CALIBRE
UCA93 I2C Communications Adapter
Issue 1.0
01/07/2003
Calibre UK Ltd 2003
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CALIBRE
Contents
INTRODUCTION
1
1
1
1.1. General Introduction
1.2. Packing List
1.3. Configuring the Adapter
1.4. Bus Termination and Protection
1
1
1.5. Connecting the Adapter to your System
1.6. Bus Capacitance Limitations/Cable Choice
1.7. Variable Voltage Bus Power Supply
INSTALLING THE ADAPTER UNDER WINDOWS
2.1. Introduction
1
2
2
3
3
2.2. Installing the Adapter
LIBRARIES FOR PROGRAMMING IN MICROSOFT WINDOWS ENVIRONMENTS
3.1. Introduction
3
4
4
3.2. Function Prototypes
5
3.3. Function Description
3.3.1. Setup
7
7
3.3.2. SendAddress
7
3.3.3. WriteByte
8
3.3.4. ReadByte
8
3.3.5. SendStop
8
3.3.6. Restart
8
3.3.7. GetStatus
9
3.3.8. Recover
9
3.3.9. SlaveLastByte
9
3.3.10. BlockWrite
3.3.11. SetBlockData
3.3.12. BlockWriteStatus
3.3.13. BlockRead
3.3.14. GetBlockData
3.3.15. BlockReadStatus
3.3.16. BlockSlaveTransmittter
3.3.17. BlockSlaveTransmitterStatus
3.3.18. BlockSlaveReceiver
3.3.19. BlockSlaveReceiverStatus
3.3.20. CheckBusVoltage
3.3.21. CheckPullupVoltage
3.3.22. Write_IO_Pin
3.3.23. Read_IO_Pin
3.3.24. SendAddressNoStatus
3.3.25. WriteByteNoStatus
3.3.26. ReadByteNoStatus
3.3.27. SendStopNoStatus
3.3.28. RestartNoStatus
10
10
10
10
11
11
11
12
12
13
13
13
14
14
15
15
15
15
16
17
18
19
22
22
22
The Real-Time Bus Monitor
Appendix A I2C Communications Adapter Status Codes
Appendix B Migration Notes for Existing Calibre I2C Customers
When the THE MOST COMMONLY ASKED I2C QUESTIONS
General Questions
Windows Questions
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CALIBRE
INTRODUCTION
1.1.
General Introduction
The UCA93 is a USB V1.1 to I2C Adapter based on the PIC 16F874 microcontroller using a Philips
PCF8584 for the bus monitor function. It features full I2C bi-directional compatibility as either a master or
slave. I2C connections are made via a 9 way “D” socket. This product complies with the requirements of
EEC Directive 89/336 for EMC and is CE marked.
The UCA93 provides full software control of the I2C bus voltage, bus speed and pull up resistors. Two
spare IO pins are available to the user.
The software functions supplied with the Adapter have been designed to feel as familiar as possible to
customers with existing Calibre AT or PCI bus I2C adapters. Nevertheless there are some unavoidable
differences between the way the UCA93 works and previous generations of products. Customers are
strongly recommended to read Appendix B which deals with migration issues.
New software block functions have been added to take advantage of the USB port’s high data rate.
1.2.
Packing List
Your I2C Communications Adapter is supplied with the following items:-
A.
B.
I2C CD ROM
The UCA93 Adapter and USB cable
1.3.
Configuring the Adapter
NOTE
There are no user adjustable components within the Adapter. The Adapter contains static
sensitive devices.
Read the following section to change the configuration.
1.4.
Bus Termination and Protection
Normally the system to which the I2C Communications Adapter is to be connected should already have
master pull up resistors fitted to the SCL and SDA lines. If this is not the case, pull up resistors to the
+V(adjustable) can be configured as part of the software set up.
1.5.
Connecting the Adapter to your System
The USB cable MUST be connected between the PC and the Adapter.
All I2C connections are made via a 9 way “D” socket:
Pin
1
Function
0V
2
0V
3
0V
4
0V
5
NC
6
7
8
9
SDA (Bi-directional)
+V (variable voltage)
SCL (Bi-directional)
NC
The Adapter also provides two digital input / output pins, which are connected via a 0.1” 4 way PCB
connector.
IO 0 is an open drain output which requires an external pull up and can be used on systems which are
not 5V tolerant. If IO 0 is used as an input it MUST be connected to a 5V system.
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IO 1 is a 5V TTL input and can only be used on 5V tolerant systems.
Pin
1
Function
NC – DO NOT CONNECT
2
3
4
IO 0
IO 1
0V
1.6.
Bus Capacitance Limitations/Cable Choice
The maximum allowable capacitance on the I2C bus in normal mode depends on the value of the SCL
and SDA master pull-ups, but never exceeds 400pF. Refer to Phillips Technical Handbook Book 4 Parts
12a and 12b for further details. Care should be taken in choosing a length and type of interconnecting
cable, which will not exceed this limit.
For most systems with a distance of a few metres between the I2C Communications Adapter and the
target system, screened cable is NOT recommended, as it is likely to introduce too much capacitance.
However, the EMC performance of an unscreened cable is always potentially poorer than a screened
one. The Adapter's EMC performance even with an unscreened cable is good - but this may not be true
of the target system! If you are in any doubt at to the best way to connect up your system with EMC in
mind please contact your supplier or Calibre for advice.
1.7.
Variable Voltage Bus Power Supply
Pin 7 on the “D” connector is connected to the variable bus voltage power rail. Power for external
circuitry can be drawn from here, but care should be taken never to short it to 0V or to exceed 250mA
loading. It is short circuit and overload protected by a self-resetting thermal fuse but prolonged shorting
could cause the UCA93 to generate an excessive amount of heat.
The bus voltage is set via software, in the range 2V to 5V.
NOTE that if a bus voltage greater 4.2V is selected the output will be 5V.
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INSTALLING THE ADAPTER UNDER WINDOWS
2.1.
Introduction
2
This section details the installation of the UCA93 I C communications Adapter under Windows 98® /
Windows2000® and Windows XP®.
The appearance of the dialog boxes during the installation of new hardware varies depending on the
version of Windows.
The Adapter supports plug and play via the USB port.
2.2.
Installing the Adapter
Connect the Adapter to the PC using the USB cable, the power light will illuminate.
The operating system will detect the installation of new hardware, follow the set up wizard instructions.
Either browse the CD or select the “have disc” option select the FTD2XX.inf.
The wizard will then install the device drivers.
IMPORTANT NOTE
Windows XP includes a driver for the USB interface device used in the Adapter, and will normally install
this. The driver installed from the XP disc WILL NOT WORK with this Adapter.
If you are using Windows XP you can check that the correct driver is installed by
1)
2)
3)
4)
5)
Right click on the “My Computer Icon”
Select properties
Select the Hardware Tab and click “Device Manager”
Expand the “Universal Serial Bus Controllers”
If the driver is provided by Microsoft you need to select the update driver then browse
for and select the FTD2XX.inf
6)
Once installed correctly the FTDI FT8U2XX Device should be listed
PLEASE NOTE The FTD2XX.inf is NOT digitally signed but is correct.
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LIBRARIES FOR PROGRAMMING IN MICROSOFT WINDOWS ENVIRONMENTS
3.1.
Introduction
Each utility is documented in a standard format which lists its name, usage, function and effect on the
Adapter is given. The Adapter should be setup prior to any data transfer.
Within the DLL there are two versions of some functions e.g. SendAddress and SendAddressNoStatus,
the first provides legacy support for software written for other Calibre UK Ltd I2C products, the second
format does not return the status.
3.1.1. Legacy Function
The following changes have had to be made to the legacy functions
1) The parameters passed to the setup function are specific to the Adapter
2) The status wait has been removed and is now controlled by hardware, the Adapter will wait up
to 500 micro seconds before returning an error code indicating that the transfer failed.
3) The Setnack is now changed on the read you require the acknowledge state to change NOT on
the byte before.
4) There is no longer a need to perform a Trash read after a restart.
3.1.2. No Status Functions
The xxNoStatus functions provide faster transfers as they do not require the USB bus to change
direction between writing and reading. The function prototypes are included in the manual but care
MUST be taken when using these functions not to corrupt the I2C with uncontrolled transfers. These
functions are ONLY to be used when users are 100% certain that all devices on the I2C WILL
acknowledge their address and that there is a single master.
PLEASE NOTE NO TECHNICAL SUPPORT IS AVAILABLE FOR THESE FUNCTIONS
Calibre UK recommend using the block functions detailed below
3.1.3. Block Functions
To aid users wishing to transfer data without the complication of having to write a I2C transfer protocol a
number of Block functions have been added. DO NOT exceed the data transfer limitations described in
the individual functions as this will cause errors and data corruption.
C and C++ users will undoubtedly wonder why they are passing data to the DLL when they could much
more efficiently pass a pointer, unfortunately not all the development environments this Adapter will be
used on support pointers.
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3.2.
Function Prototypes
If you are using ‘C’ or ‘C++’ copy the file CALUCA.H into the directory containing your project and add
the line:
#include " CALUCA.H"
The following functions are implemented in the windows libraries:-
extern __declspec(dllimport) int WINAPI Setup (int, int, int, int, int);
extern __declspec(dllimport) int WINAPI SendAddress (int, int);
extern __declspec(dllimport) int WINAPI WriteByte(int);
extern __declspec(dllimport) int WINAPI ReadByte(int);
extern __declspec(dllimport) int WINAPI SendStop(void);
extern __declspec(dllimport) int WINAPI Restart (int, int);
extern __declspec(dllimport) int WINAPI GetStatus(void);
extern __declspec(dllimport) int WINAPI recover(void);
extern __declspec(dllimport) void WINAPI SlaveLastByte(void);
extern __declspec(dllimport) int WINAPI DLLVersion(void);
extern __declspec(dllimport) void WINAPI SendAddressNoStatus(int , int, int);
extern __declspec(dllimport) void WINAPI RestartNoStatus(int , int, int );
extern __declspec(dllimport) void WINAPI WriteByteNoStatus(int );
extern __declspec(dllimport) void WINAPI ReadByteNoStatus(int );
extern __declspec(dllimport) void WINAPI SendStopNoStatus(void);
extern __declspec(dllimport) int WINAPI SetBlockData(int);
extern __declspec(dllimport) int WINAPI BlockWriteStatus (void);
extern __declspec(dllimport) int WINAPI BlockWrite(int , int , int ,int, int );
extern __declspec(dllimport) int WINAPI GetBlockData(void);
extern __declspec(dllimport) int WINAPI BlockReadStatus(void);
extern __declspec(dllimport) int WINAPI BlockRead(int , int , int , int, int );
extern __declspec(dllimport) int WINAPI BlockSlaveTransmitterStatus(void);
extern __declspec(dllimport) int WINAPI BlockSlaveTransmitter( int );
extern __declspec(dllimport) int WINAPI BlockSlaveReceiverStatus(void);
extern __declspec(dllimport) int WINAPI BlockSlaveReceiver(int , int );
extern __declspec(dllimport) int WINAPI Write_IO_Pin (int , int );
extern __declspec(dllimport) int WINAPI Read_IO_Pin (int );
extern __declspec(dllimport) int WINAPI CheckBusVoltage(void);
extern __declspec(dllimport) int WINAPI CheckPullupVoltage(void);
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If you are using Visual Basic copy the file UCA93LV.BAS into the directory containing your project and
add the file UCA93LV.BAS to your project:
The following functions are implemented in the windows libraries:-
Public Declare Function Setup% Lib "USBDLL_XP.dll" (ByVal OwnAddress%, ByVal Sclk%, ByVal
BusVoltage%, ByVal PullUpsOn%, ByVal SlaveBlockTimeout%)
Public Declare Function SendAddress% Lib "USBDLL_XP.dll" (ByVal SlaveAddress%, ByVal setnack%)
Public Declare Function Restart% Lib "USBDLL_XP.dll" (ByVal SlaveAddress%, ByVal setnack%)
Public Declare Function WriteByte% Lib "USBDLL_XP" (ByVal wrdata%)
Public Declare Function ReadByte% Lib "USBDLL_XP.dll" (ByVal setnack%)
Public Declare Function SendStop% Lib "USBDLL_XP.dll" ()
Public Declare Function GetStatus% Lib "USBDLL_XP.dll" ()
Public Declare Function Recover% Lib "USBDLL_XP.dll" ()
Public Declare Function SlaveLastByte% Lib "USBDLL_XP.dll" ()
Public Declare Function DLLVersion% Lib "USBDLL_XP.dll" ()
Public Declare Function SetBlockData% Lib "USBDLL_XP.dll" (ByVal DataVal%)
Public Declare Function GetBlockData% Lib "USBDLL_XP.dll" ()
Public Declare Function BlockSlaveTransmitter% Lib "USBDLL_XP.dll" (ByVal TimeOut%)
Public Declare Function BlockSlaveTransmitterStatus% Lib "USBDLL_XP.dll" ()
Public Declare Function BlockSlaveReceiver% Lib "USBDLL_XP.dll" (ByVal NoBytesToTransmit%,
ByVal TimeOut%)
Public Declare Function BlockSlaveReceiverStatus% Lib "USBDLL_XP.dll" ()
NOTE A type is defined in UCA93LV.BAS to help passing parameters to the DLL, if you do not
wish to use this local variables MUST be declared as static
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3.3.
Function Description
3.3.1.
Setup
Function specification int Setup(int OwnAddress, int ClockSpeed, int BusVoltage, int PullUpsOn, int
SlaveBlockTimeout)
Parameters are:
int ownaddress
This is the I2C address to which the Adapter is to respond in slave mode. This
forms the upper 7 bits of the 8 bit address, the lowest bit being the read(1) or
write(0) bit. This means that if ownaddress = 57H the card will respond to a
write address of AEH and a read address of AFH.
int ClockSpeed
2
This is the clock rate (bit rate for the I C serial bus) when operating as a
master. For 400kHz enter 400, for 90kHz enter 90.
Maximum value 400 minimum value 25
int BusVoltage
The desired bus voltage multiplied by 100 e.g. 330 would give a bus voltage
3.3V. Please note that if a value between 4.2V and 5V is requested the output
will be 5V.
Maximum value 500 (5V) Minimum value 180 (1.8V).
int PullUpsOn
Set (1) to turn the pull up resistors on, clear (0) to turn them off.
int SlaveBlockTimeout
This parameter is only used by the slave block functions. If the Master has not
completed the transfer in this period (seconds) the Adapter will abort the
transfer and return an error code.
Range 1 – 255 seconds. NOTE: setting this value to 0 will prevent the Adapter
from timing out the slave block function.
Parameters returned
Prerequisites
If the software fails to find the driver error code 8000H is returned otherwise the
status is returned.
None.
2
Functional description This function initialises Adapter ready for I C transfers.
3.3.2.
SendAddress
Function specification Int SendAddress(int SlaveAddress, int SetNack)
Parameters are:
int SlaveAddress
This is the address to be accessed via the I2C, e.g. A0H.
int SetNack
2
This controls whether the Adapter transmits an acknowledge down the I C bus
on reception of a byte. The last byte received during a transfer must not be
acknowledged, in all other cases acknowledge must be enabled. If SetNack = 0
then acknowledge is enabled, if SetNack = 1 then acknowledge is disabled.
Normally there will be another transfer (data read or write) after the
SendAddress and so SetNack is enabled (0);
Parameters returned
Prerequisites
int ErrCode.
If the transfer time out occurs error code 8001H is returned otherwise the
status is returned.
The Adapter must be configured by running Setup.
Functional description The function waits for the bus to be free then sends the slave address.
The function waits for the address to be sent. Should a time-out occur during
the sending of an address then an error code 8001H is returned, otherwise the
status is returned.
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WriteByte
Function specification Int WriteByte(int DataByte)
Parameters are:
int DataByte
This is the byte of data to be written.
Parameters returned
int ErrCode.
If the transfer time out occurs error code 8002H is returned otherwise the
status is returned.
Prerequisites
Adapter must be configured using Setup, start and write address sent by
SendAddress.
Functional description The function writes the data to the Adapter and then waits for it to be sent.
Should a time-out occur during the sending of the data then error code 8002H
is returned, otherwise the status is returned.
WriteByte is compatible with both master write and slave write modes.
3.3.3.
ReadByte
Function specification Int ReadByte(int SetNack)
Parameters are:
int SetNack
2
This controls whether the Adapter transmits an acknowledge down the I C bus
on reception of a byte. The last byte received during a transfer must not be
acknowledged, in all other cases acknowledge must be enabled. If SetNack = 0
then acknowledge is enabled, if SetNack = 1 then acknowledge is disabled.
int I2CData
If a time-out occurs the ErrCode 8003H is returned, otherwise the data is
returned.
Parameters returned
Prerequisites
Adapter must be configured using Setup, start and read address sent by
SendAddress.
Functional description The data is read from the Adapter.
ReadByte is compatible with both master read and slave read modes.
3.3.4.
SendStop
Function specification Int SendStop(void)
Parameters are:
None
Parameters returned
int ErrCode.
If the transfer time out occurs error code 8006H is returned otherwise the
status is returned.
Prerequisites
Adapter must be configured using Setup. Should normally only be used at the
end of a transmission. Correct acknowledge sequence must have been applied
if the transmission was a read.
Functional description Instructs the Adapter to send a stop code and wait for it to be sent.
Should a time-out occur during the sending of a stop then an error code 8006H
is returned, otherwise the status is returned.
3.3.5.
Restart
Function specification Int Restart(int SlaveAddress, int SetNack)
Parameters are:
int slaveaddress
The address to be accessed via the I2C, e.g. A1H.
int SetNack
2
This controls whether the Adapter transmits an acknowledge down the I C bus
on reception of a byte. The last byte received during a transfer must not be
acknowledged, in all other cases acknowledge must be enabled. If SetNack = 0
then acknowledge is enabled, if SetNack = 1 then acknowledge is disabled. It is
normal to read data after a restart and hence SetNack will normally be 0.
int ErrCode
Parameters returned
Prerequisites
If the transfer time out occurs error code 8004H is returned otherwise the
status is returned.
Adapter must be configured using Setup. A start and slave address must have
previously been sent using SendAddress.
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Usually a data pointer would already have been written using WriteByte.
Functional description Sends a start code and the slave address.
The function waits for the address to be sent. Should a time-out occur during
the sending of an address then an error code 8004H is returned, otherwise the
status is returned.
3.3.6.
GetStatus
Function specification: Int GetStatus(void)
Parameters are:
None
Parameters returned
int I2Cstatus
The current value of the bus status is returned.
Adapter must be configured using Setup.
Prerequisites
Functional description The function reads status word from the Adapter and returns it.
3.3.7.
Recover
Function specification Int Recover(void)
Parameters are:
None
Parameters returned
int ErrCode.
If the bus recovery failed error code 800FH is returned otherwise the status is
returned.
Prerequisites
Adapter must be configured using Setup.
Functional description This function clears all USB buffers and issues three consecutive stop
commands on the bus, with a delay of about 5uS in between. It then clears the
Adapter registers and reads the status. This should normally set the Adapter
into a known idle state when a bus error or other problem has occurred.
If the status does not indicate bus free or the Bus Error bit is still set then
800FH is returned otherwise the status is returned.
3.3.8.
SlaveLastByte
Function specification void SlaveLastByte(void)
Parameters are:
Parameters returned
Prerequisites
None
None.
Adapter must be configured using setup. This function would normally only be
called following the end of a transmission in slave write mode - when the
Adapter is being read as a slave, by another master, not when writing to a slave
using the Adapter.
Functional description This function is used when the Adapter is a slave being read by a master
elsewhere on the bus - the Adapter is in slave write mode. The function must
be called immediately after the master indicates the last byte has been read (by
2
not acknowledging that byte). This function is required to clear the I C data
lines so that the master can send a stop signal.
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3.3.9.
BlockWrite
Function specification void BlockWrite(int SlaveWriteAddress, int MSB_WordAddress, int
LSB_WordAddress,int NoBytesToSend, int NoTries )
Parameters are:
int SlaveAddress
This is the address to be accessed via the I2C, e.g. A0H
int MSB_WordAddress, int LSB_WordAddress
This is the location within the slave for the data. The use of two bytes allows
users to communicate with devices requiring two byte pointers e.g. 24C64
EEPROMS. If one (or both) of the word addresses are not required set the
value to a number greater than 255 and it will not be transmitted.
int NoBytesToSend
The number of bytes to be sent which MUST be pre loaded into the driver
buffers. The maximum size of this buffer is 2048 exceeding this WILL cause
the data to be corrupted.
Int NoTries
This is the number of times the Adapter is to try to send the address.
Parameters returned
Prerequisites
None.
Adapter must be configured using Setup. The data MUST be loaded into the
driver buffers PRIOR to calling this functions (see SetBlockData).
Functional description This function causes the Adapter to send a block of data via the I2C bus.
3.3.10.
SetBlockData
Function specification int SetBlockData(int DataVal)
Parameters are:
Parameters returned
Prerequisites
Int DataVal
Returns an unused integer.
Adapter must be configured using setup.
Functional description This stores data in the driver buffers read to be sent by the BlockWrite function.
MAXIMUM DATA SIZE 2048 bytes.
3.3.11.
BlockWriteStatus
Function specification int BlockWriteStatus (void))
Parameters are:
None
Parameters returned
int TransferStatus.
Returns 0 if the transfer has not been completed.
Returns the I2C Bus status if the transfer is completed.
Returns 9009H if the transfer time out.
Adapter must be configured using Setup. Data must have been sent using the
BlockWrite function.
Prerequisites
Functional description Returns the current status of the BlockWrite transfer NOTE this function will
time out if the block is not sent in NoBytes / 100 seconds (or 1 second which
ever is the greater).
3.3.12.
BlockRead
Function specification void
BlockRead(int
SlaveAddress,
int
MSB_WordAddress,
int
LSB_WordAddress, int NoBytesToRead, int NoTries )
Parameters are:
int SlaveAddress
This is the address to be accessed via the I2C, e.g. A0H If the SlaveAddress is
is a read address then the Word Addresses WILL NOT be sent.
int MSB_WordAddress, int LSB_WordAddress
This is the location within the slave for the data. The use of two bytes allows
users to communicate with devices requiring two byte pointers e.g. 24C64
EEPROMS. If one (or both) of the word addresses are not required set the
value to a number greater than 255 and it will not be transmitted.
int NoBytesToRead
The number of bytes to be sent which MUST be pre loaded into the driver
buffers. The maximum size of this buffer is 2048 exceeding this WILL cause
the data to be corrupted.
Int NoTries
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This is the number of times the Adapter is to try to send the address.
Parameters returned
Prerequisites
None.
Adapter must be configured using setup.
Functional description This function causes the Adapter to read a block of data via the I2C bus.
3.3.13.
GetBlockData
Function specification int GetBlockData(void)
Parameters are:
Parameters returned
Prerequisites
None
int RdData.
Adapter must be configured using Setup. The block read function MUST have
been called and the BlockReadStatus should be called to determine if the
transfer has been completed
Functional description Read data from the driver buffers. MAXIMUM DATA SIZE 2048 bytes.
3.3.14.
BlockReadStatus
Function specification int BlockReadStatus (void))
Parameters are:
None
Parameters returned
int TransferStatus.
Returns 0 if the transfer has not been completed.
Returns the I2C Bus status if the transfer is completed.
Returns 900AH if the transfer time out.
Adapter must be configured using Setup. The transfer must be started using
the BlockRead function.
Prerequisites
Functional description Returns the current status of the BlockWrite transfer NOTE this function will
time out if the block is not sent in NoBytes / 100 seconds (or 1 second which
ever is the greater).
3.3.15.
BlockSlaveTransmittter
Function specification int BlockSlaveTransmitter(int NoBytesToTransmit, int Timeout)
Parameters are:
int NoBytesToTransmit
The number of bytes to be sent which MUST be pre loaded into the driver
buffers. The maximum size of this buffer is 2048 exceeding this WILL cause
the data to be corrupted.
Int Timeout
If the transfer is not completed within Timeout seconds the
BlockSlaveTansmitStatus will return a Timeout error.
Returns an unused integer.
Adapter must be configured using Setup. The data MUST be loaded into the
driver buffers PRIOR to calling this functions (see SetBlockData).
Parameters returned
Prerequisites
Functional description This function causes the Adapter to respond to I2C master requests for data.
This function supports transfers where the master sends WordAddress pointers
to data locations within the transfer block. If the master does not request to
read data from the beginning of the data block the Adapter will remove the data
from the buffer until the byte requested by the master is reached it will then
transmit the data.
Should the master exceed the number of bytes available the Adapter will
honour all requests for data and the overflow will be reported see
BlockSlaveTransmitterStatus.
This function allows the user to emulate simple slave devices e.g. EEPROM
BUT once the master has completed the transfer the Adapter will NOT respond
to any further requests for data until the BlockSlaveTransmitter is called again.
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3.3.16.
BlockSlaveTransmitterStatus
Function specification int BlockSlaveTransmitterStatus (void))
Parameters are:
None
Parameters returned
int TransferStatus.
Returns 0 if the transfer has not been completed.
Returns the a status if the transfer is completed (see below).
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Set if a write address received
Set if word address 0 received
Set if word address 1 received
Set if restart received
Stop detected
Set if the transfer timeout (Value in Setup function) occurred
Returns 900BH if the transfer time out.
Prerequisites
Adapter must be configured using Setup. The transfer must be started using
the BlockSlaveTransmittter function.
Functional description Returns the current status of the BlockSlaveTransmittter transfer NOTE this
function will time out the BlockSlaveTransmittter function.
Read two bytes of data from the Adapter using GetBlockData to determine
where the master read from in the block (high byte first), read the next two
bytes to determine how many bytes of data the master read from the slave
(high byte first), read 1 byte to determine the status.
3.3.17.
BlockSlaveReceiver
Function specification int BlockSlaveReceiver (int NoBytesToReceive, int Timeout)
Parameters are:
int NoBytesToReceive
The number of bytes to expected from the master. NOTE if the protocol
requires the master to transmit one or more word address bytes these MUST
be included in the NoBytesToReceive. The maximum size of this buffer is 2048
exceeding this WILL cause the data to be corrupted.
PLEASE NOTE THIS MUST INCLUDE THE NUMBER OF WORD ADDRESS
BYTES IF THEY ARE TRANSMITTED BY THE MASTER
Int Timeout
If the transfer is not completed within Timeout seconds the
BlockSlaveReceiverStatus will return a Timeout error.
Returns an unused integer.
Parameters returned
Prerequisites
Adapter must be configured using Setup.
Functional description This function causes the Adapter to respond to I2C master transmission of
data. This function supports transfers where the master sends WordAddress
pointers to data locations within the transfer block.
Should the master exceed the number of bytes expected the Adapter will
honour all transfers for data and the overflow will be reported see
BlockSlaveReceiverStatus.
This function allows the user to emulate simple slave devices e.g. EEPROM
BUT once the master has completed the transfer the Adapter will NOT respond
to any further requests for data until the BlockSlaveReceiver is called again.
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3.3.18.
BlockSlaveReceiverStatus
Function specification int BlockSlaveReceiverStatus (void))
Parameters are:
None
Parameters returned
int TransferStatus.
Returns 0 if the no data has been received.
Returns the a status if the transfer is completed (see below).
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Not Used
Not Used
Not Used
Not Used
Stop detected
Set if the transfer timeout (Value in Setup function) occurred
Returns 900DH if the expected number of bytes is exceeded
Returns 900CH if the transfer time out.
Prerequisites
Adapter must be configured using Setup. The transfer must be started using
the BlockSlaveReceiver function.
Functional description Returns the current status of the BlockSlaveReceiver transfer NOTE this
function will time out the BlockSlaveReceiver function.
Read two bytes of data from the Adapter using GetBlockData to determine how
many bytes of data the master read from the slave.
Read the first two bytes to determine how many bytes of data the master read
from the slave (high byte first), read 1 byte to determine the status.
3.3.19.
CheckBusVoltage
Function specification int CheckBusVoltage (void))
Parameters are:
None
Parameters returned
int BusVoltage
Returns the I2C bus output voltage multiplied by 100.
Returns 0x800C if the transfer timed out.
Adapter should be configured using Setup. If this is not done the I2C bus
voltage will default to 3.3V.
Prerequisites
Functional description Returns the current bus voltage multiplied by 100 as measured on pin 7 of the
output socket. For example, will return 330 for a 3.3V bus voltage , 500 for a
5.0V bus voltage and 200 for a 2.0V bus voltage.
3.3.20.
CheckPullupVoltage
Function specification int CheckPullupVoltage (void))
Parameters are:
None
Parameters returned
int PullupVoltage
Returns the I2C pullup voltage multiplied by 100 measured upstream of the
output overcurrent protection device.
Returns 0x800C if the transfer timed out.
Adapter should be configured using Setup. If this is not done the I2C bus
voltage will default to 3.3V.
Prerequisites
Functional description The pullup voltage is the same as the I2C output voltage but measured
upstream of the resettable polyfuse protection device. Returns the current
pullup voltage multiplied by 100. For example, will return 330 for a 3.3V pullup
voltage , 500 for a 5.0V pullup voltage and 200 for a 2.0V pullup voltage. If the
pullup voltage differs from the bus voltage (measured by the previous function)
by more than a few tens of millivolts then too much current is being drawn from
the Adapter. No more than 250mA should be drawn from the Adapter.
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3.3.21.
Write_IO_Pin
Function specification int Write_IO_Pin (int IONumber, int IOState)
Parameters are:int IONumber
The number of the IO pin (0 or 1) to be driven
int IOState
The required state (0 or 1) of the selected IO pin
Parameters returned
Prerequisites
int
Returns a 0 if function successful.
Returns 0x800D if the transfer timed out.
None
Functional description Two spare IO pins are available to drive external logic. IO0 is on PL1 pin 2 and
is an open drain driver. When driven low it can sink up to 10mA, when high it is
high impedance and cannot source current. A pullup resistor should be fitted to
the desired rail which should not exceed +5V. IO1 is on PL1 pin 3 and is a
complementary driver which can source or sink up to 10mA. Its logic levels are
fixed at 0V and +5V nominal.
3.3.22.
Read_IO_Pin
Function specification int Read_IO_Pin (int IONumber)
Parameters are:int IONumber
The number of the IO pin (0 or 1) to be read
int
Parameters returned
Returns the state (0 or 1) of the chosen IO pin if function successful.
Returns 0x800D if the transfer timed out.
Prerequisites
None
Functional description Two spare IO pins are available which can be driven by external logic. IO0 is
on PL1 pin 2 and IO1 is on PL1 pin 3. These pins are normally high impedance
input unless specifically driven by the Write_IO_Pin function. They can be
driven high or low by external logic then read by the Read_IO_Pin function.
Normal 5V CMOS logic levels (0 < 1.5V, 1 > 3.5V) should be applied for reliable
reading.
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3.3.23.
SendAddressNoStatus
Function specification void SendAddressNoStatus(int SlaveAddress, int SetNack, int NoTries)
Parameters are:
int SlaveAddress
This is the address to be accessed via the I2C, e.g. A0H.
int SetNack
2
This controls whether the Adapter transmits an acknowledge down the I C bus
on reception of a byte. The last byte received during a transfer must not be
acknowledged, in all other cases acknowledge must be enabled. If SetNack = 0
then acknowledge is enabled, if SetNack = 1 then acknowledge is disabled.
Normally there will be another transfer (data read or write) after the
SendAddress and so SetNack should be enabled (0);
Int NoTries
This is the number of times the Adapter is to try to send the address.
Parameters returned
Prerequisites
None.
The Adapter must be configured by running Setup.
Functional description The function waits for the bus to be free. Then sends the slave address with the
appropriate acknowledge.
The acknowledge must equal 0.
The function will generate a start and send the address. If the slave does not
acknowledge then the Adapter will generate a stop. It will try to send the
address a number of times equal to NoTries.
3.3.24.
WriteByteNoStatus
Function specification void WriteByteNoStatus(int DataByte)
Parameters are:
int DataByte
This is the byte of data to be written.
Parameters returned
Prerequisites
None.
Adapter must be configured using Setup, start and write address sent by
SendAddressNoStatus.
Functional description The function writes the data to the Adapter and then waits for it to be sent.
WriteByteNoStatus is compatible with both master write and slave write modes.
3.3.25.
ReadByteNoStatus
Function specification Int ReadByte(int SetNack)
Parameters are:
int SetNack
2
This controls whether the Adapter transmits an acknowledge down the I C bus
on reception of a byte. The last byte received during a transfer must not be
acknowledged, in all other cases acknowledge must be enabled. If SetNack = 0
then acknowledge is enabled, if SetNack = 1 then acknowledge is disabled.
None
Adapter must be configured using Setup, start and read address sent by
SendAddressNoStatus.
Parameters returned
Prerequisites
Functional description The data is read from the Adapter.
ReadByteNoStatus is compatible with both master read and slave read modes.
3.3.26.
SendStopNoStatus
Function specification void SendStopNoStatus(void)
Parameters are:
Parameters returned
Prerequisites
None
None.
Adapter must be configured using Setup. Should normally only be used at the
end of a transmission.
Functional description Instructs the Adapter to send a stop code and wait for it to be sent.
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3.3.27.
RestartNoStatus
Function specification void RestartNoStatus(int SlaveAddress, int SetNack, int NoTries)
Parameters are:
int SlaveAddress
The address to be accessed via the I2C, e.g. A1H.
int SetNack
2
This controls whether the Adapter transmits an acknowledge down the I C bus
on reception of a byte. The last byte received during a transfer must not be
acknowledged, in all other cases acknowledge must be enabled. If SetNack = 0
then acknowledge is enabled, if SetNack = 1 then acknowledge is disabled. It is
normal to read data after a restart and hence SetNack will normally be 0.
Int NoTries
This is the number of times the Adapter is to try to send the address
Parameters returned
Prerequisites
None
Adapter must be configured using Setup. A start and slave address must have
previously been sent using SendAddressNoStatus.
Usually
a
data pointer would already have been written using
WriteByteNoStatus.
Functional description Sends a start code and the slave address.
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The Real-Time Bus Monitor
To install the monitor run the setup program located in the \CD_USB\USB_Monitor folder, follow the
instructions given by the installation wizard.
Before attempting to run the monitor program ensure that the device drivers are installed correctly in
accordance with this manual.
The program UI2C_MONITOR.EXE is a windows based non-invasive real-time bus monitor which
records activity on an I2C-bus. The transfers are processed into a simple to read format which can be
saved to the PC hard disc.
The monitor can be configured to capture all transfers or alternatively it can capture all transfers
between a start and end address. These features allow the user to capture only those transfers which
are of interest.
Every effort has been made to ensure that the monitor captures all of the transfers it is possible that the
program may miss part of a transfer on heavily loaded I2C buses, this is due to the operating system
servicing other hardware and / or applications. To minimise the amount of data missed we recommend
that you close as many windows applications as possible especially all windows messaging applications,
e-mail and FindFast. We also recommend that you run the application from a 900MHz PC (or better),
note the application will run on a lesser specification PC but you are likely to miss more data.
The following mnemonics are used by the monitor program.
SaXX Start code followed by address, acknowledged.
SnXX Start code followed by address, not acknowledged.
DaXX Data byte, acknowledged.
DnXX Data byte, not acknowledged.
STOP Stop code.
BUS ERROR A bus error has occurred. This is non-fatal to the monitor but a small amount of data
may have been lost whilst recovery was taking place.
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Appendix A I2C Communications Adapter Status Codes
This is an eight bit register, read using the GetStatus routine. Each individual bit has its own meaning as
follows:
Bit 7 (MSB) - The (old) PIN Bit
To all intents and purposes, this bit is now redundant. Previous Calibre I2C products used this bit to
synchronise data transfers between the I2C bus and the host PC. On the UCA93 synchronisation is
achieved by the Adapter returning a status byte to the host when the requested function has completed
or timed out. Whereas the value of the PIN bit used to be important, now it is whether or not the status
byte has been returned to the host that is important. The PIN bit roughly mimics the behaviour of the
old products so that customers still feel comfortable with it, but software should not rely on it. Other bits
in the status word are still important, and should be interpreted as below.
Bit 6 – The Timeout Bit Normally this bit should read as a 0. If it is set the Adapter timed out when
attempting some master activity. This could mean that another master has control of the bus or that a
bus error has occurred or that a slave device is seriously slowing down the bus. Timeout normally
occurs about 500uS after a master function is requested. This is a new bit which was not implemented
on previous generations of Calibre products.
Bit 5 - The (old) STS Bit
This bit normally reads as a 0 and is set this way only as legacy support. On previous Calibre I2C
products indicated that a stop had been detected whilst in slave receiver mode. Software should not rely
on this bit.
Bit 4 - The BER (Bus Error) Bit
This bit should normally read as a 0. It is set high when a misplaced Start or Stop has been detected.
This can be quite serious since the I2C devices on the bus may be left in an undefined state after a bus
error has occurred - in some circumstances the only way to get the bus going again may be to reset all
the I2C devices on it.
Bit 3 - The Ack Bit
This bit indicates the state of the 9th I2C bit which is the acknowledge bit. It is active low so reads as 0
for if the receiver acknowledged and 1 if the receiver did not acknowledge. In a master SendAddress or
Restart function it indicates whether the slave is present or not. In a master write operation it indicates
whether the slave acknowledged the data byte or not, in a master read it indicates whether or not the
master was requested to acknowledge the data from the slave or not.
Bit 2 - The (old) AAS Bit
This bit should normally read as a 0 and is set this way for legacy support. On previous Calibre I2C
products indicated that a device had been addressed whilst in a slave mode. Software should not rely
on this bit.
Bit 1 - The LAB (Lost Arbitration) Bit
This bit should read as a 0. It is set = 1 when, in multimaster operation (more than one master present
on the I2C bus) arbitration is lost to another master on the I2C bus.
Bit 0 - The BB (Bus Busy) Bit
This bit reads as a 1 when the bus is idle. Once a Start has been detected it goes low and stays low
until the transfer is terminated correctly with a Stop. New transmissions should therefore not be
attempted if this bit is low – it may be that another master has control. If there is no other master on the
system it may be that a slave is stuck or a bus error has occurred in which case a Recover may free up
the bus.
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Appendix B Migration Notes for Existing Calibre I2C Customers
These notes are intended for customers who have code working on one or more of Calibre UK’s
existing AT or PCI based adapters and wish to convert it to work with the new UCA93 Adapter. The
fundamental differences are a much reduced reliance on polling the status register, a new way of calling
slave functions and the introduction of new block transfer functions.
USB Bus Characteristics
The USB V1.1 bus is fast – data transfer rates can approach a 1 million 8-bit bytes per second. A brief
period of USB bus housekeeping is performed at 1mS intervals then the rest of that 1mS time slice is
available for data transfer to a particular peripheral in a particular direction. All transfers are initiated by
the host PC – it is very much in charge of the system. Direction changes cost bandwidth because even
a single byte transfer in a particular direction will occupy a time slice of 1mS. Single byte transfers in
alternate directions will effectively reduce the bus bandwidth to 1kHz! – similar to RS232. Software
functions for the UCA93 are fundamentally designed to reduce data direction changes and that is why
some of the traditional Calibre software method have had to be re-thought.
Polling the Status Register (and how to avoid it)
Traditional Calibre software requests a function (say SendAddress) then polls the status register until
the status indicates that the function has completed. On the UCA93 this is replaced by a function of the
type
I2CStatus = SendAddress(SlaveAddress);
which instructs the adapter to generate the start transmit the address then waits for a single status byte
to be returned from the adapter indicating how the transfer went. See Appendix A for details. One
status byte will always be returned even if the function fails and times out (about 500uS). Multiple polls
are not needed nor desirable and should be removed from code.
Previous Calibre I2C products used the PIN bit to synchronise data transfers between the I2C bus and
the host PC but this now is all handled by the PIC16F874 microcontroller on the Adapter.
Communication between the Adapter and host is now synchronised differently so to all intents and
purposes this bit is now redundant.
Block Functions
Block functions are I2C master functions designed to take advantage of the high bandwidth of the USB
bus whilst minimising data direction changes which slow the bus down. Instead of piecing together I2C
functions the user can for example load data into an array, then call a BlockWrite function.
Block Write Function
On receiving the BlockWrite function the adapter will generate the start and address, then optionally a
single or double pointer followed by a block of data up to 2048 bytes which is preset by the
SetBlockData function. If the slave device does not acknowledge, the adapter will send a stop after the
address, then repeat the sequence again up to Tries times to rouse the slave. If the slave still does not
acknowledge, the function will terminate cleanly. The user should keep track of the BlockWrite function
by immediately calling the BlockWriteStatus function which will return the status byte indicating how the
BlockWrite function got on and how it terminated.
Block Read Function
On receiving the BlockRead function the adapter will generate the start and address, then optionally a
single or double pointer. If the slave device does not acknowledge, the adapter will send a stop after the
address, then repeat the sequence again up to Tries times to rouse the slave. If the slave still does not
acknowledge, the function will terminate cleanly. The user should keep track of the BlockRead function
by immediately calling the BlockReadStatus function which will return the status byte indicating how the
BlockRead function got on and how it terminated. The data returned from the slave to the host via the
adapter can be accessed by calling the BlockRead function which accesses a global variable.
Slave Functions
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The slave functions of the UCA93 differ most from traditional Calibre AT and PCI bus based products.
A user must make a pre-determined decision whether to put the adapter into master, slave transmitter
or slave receiver modes. The adapter’s own address is established as part of the Setup function. If the
adapter is in master mode (the default) , it will not respond to its own address if this is generated by
another master on the system. If the adapter is in either slave mode it will recognise its own address
and an acknowledge will be generated on the I2C bus.
Slave Transmitter Function
When the BlockSlaveTransmittter function is called the user sends a data block of selectable size (max
2048bytes) into a buffer together a timeout time in seconds. When a master generates the adapter’s
own address (either write or read) the adapter will generate an acknowledge on the I2C bus.
If the address was even (master write) the adapter will assume that the master wishes to send a pointer
to a location in the data block. The pointer can be one or two bytes. If the pointer is single the upper
byte will default to 0x00. If the master fails to send a pointer both bytes will default to 0x00 and if the
master send more than two bytes on the last two will be used – the others will be discarded. Data in the
block will then be discarded so that the first byte aligns with the pointer sent. Note that the adapter will
hold SCL low during this alignment which slows down the I2C bus – the master should be able to
tolerate this.
If the address was odd (master read) the adapter will assume that the master does not wish to send a
pointer and that data transmission should start from the beginning of the data block.
If the master has sent a pointer the master should then generate a restart followed by the adapter’s read
address which will be acknowledged.
Data is then transmitted from the adapter to the master starting at the pointer location. Remembering
that the master is in charge of the length of the transfer and the generation of the stop, the adapter will
transmit data to the master for as long as required. If the transfer is longer than the available data the
last available byte in the block will be repeated; if it is shorter then not all the data in the block will be
used.
When the transmission is terminated by the master the adapter will send a single byte back to the host.
The BlockSlaveTransmitterStatus function waits for this byte and the byte is interpreted as described
the function definition. Note that this byte may return either as a result of a timeout (when the master
fails to initiate a transfer to the adapter within the timeout seconds) or the master correctly terminating
the transfer.
When the BlockSlaveTransmittter function terminates the adapter goes back into an idle state – it will
not acknowledge its own address or repeat any other slave behaviour until the slave function is called
again.
Users will note that the BlockSlaveTransmittter function is designed as much as possible to emulate the
behaviour of an EEPROM. The only differences are that the block size is limited to 2048 byte, there
may be some delay on the bus white data is aligned with the pointer and the function only runs once
without being recalled. The function is also designed to keep the transmission going even if a mistake
is made in the master’s protocol although it is important that the master generates a stop eventually.
Slave Receiver Function
The BlockSlaveReceiver function is simpler than the previous function! When it is called the user must
instruct the adapter on how many bytes it wishes to receive back (max 2048) and on a timeout in
seconds.
When the master generates the adapter’s own address the adapter will generate an acknowledge on
the I2C bus. Since the adapter is about to receive data this should be an even (write) address.
The master then transmits data to the adapter and the adapter will acknowledge each byte then put it
into the pre-determined size buffer to be transmitted to the host. The adapter will accept data from the
master for as long as the master sustains the transfer. If too much data is sent by the master, the
adapter keeps on acknowledging the master but stops putting data into the buffer. Likewise, if the
master terminates the transfer before the buffer is full, the adapter pads out the buffer with 0xFFs to the
predetermined size.
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When the master terminates the transfer, the adapter completes sending the data block to the host
together with a single status byte indicating how the transfer went, and the data is put into a global
variable. The BlockSlaveReceiverStatus function waits for this status byte and the byte can be
interpreted as in the function definition.
When the BlockSlaveReceiver function terminates the adapter goes back into an idle state – it will not
acknowledge its own address or repeat any other slave behaviour until the slave function is called again.
If the master erroneously sends a read address when the BlockSlaveReceiver function has been called
the adapter will send a fixed sequence of 0x55s until the master terminates the transfer.
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When the THE MOST COMMONLY ASKED I2C QUESTIONS
General Questions
Question
I get corrupted transfers why is this?
Answer
The most likely reason for corrupted transfers is either incorrect bus termination or
excessive capacitance - see the manual for details.
Question
Do you have software to talk to my........?
Answer
Unfortunately there are too many I2C devices for us to be able to offer complete
solutions - although we can supply a windows based application called WINI2C which is
designed for those just starting I2C or wishing to perform simple I2C tasks, please
information.
Question
I am trying to read from a device, the first time my software works fine but when I
try again I can't get anything what's wrong?
Answer
Please check that you are changing the value of Setnack in accordance with the
manual, it is likely that you have not made Setnack 1 for the last byte being read.
Windows Questions
Question
I have read the manual and still cannot get the communications to run. What do I
do next?
Answer
Check that you have fully implemented the protocol between the Adapter and the other
I2C devices see the device manufacturers data sheet for details.
Check that the software you have written is logically and syntactically correct - this is
probably the most common cause of software faults we have to deal with.
Send us the following details:-
1)The link settings of the Adapter.
2)A sketch of the relevant I2C hardware including the location of bus termination.
3)The type and speed of processor within your PC and which operating system, you are
running.
4)Brief software listings, or which Calibre software you are running.
5)The serial number of your I2C Adapter, or when you purchased it.
PLEASE EMAIL YOUR QUERY TO:
OR FAX YOUR QUERY TO:
44-1274-730960
We will endeavour to help you.
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