Hi all,

while trying to use I2C-module of FX3 some strange behaviour occured:

1.) I can't get out a speed of 1MHz on I2C-bus! If I set the bitrate in struct CyU3PI2cConfig_t to 1000000 (1MHz) I see only the I2C-startcondition on oscilloscope and then the whole I2C-bus hangs up!
Setting the bitrate to:
100kHz => works fine
400kHz => works fine
900kHz => I2C-bus shows only ~700kHz ?!
1MHz => I2C hangs up!
VIO5 is 3.2V (measured).

2.) There might be a problem with the API CyU3PI2cTransmitBytes(). The API returns in any case CY_U3P_SUCCESS, even if there is no I2C-slave available on the bus. I called the API's CyU3PI2cTransmitBytes() and CyU3PI2cWaitForAck() subsequently (using the code below) without having a slave on the bus (so there is no ACK for sure! I checked it on oscilloscope) and the API:
CyU3PI2cTransmitBytes() returned CY_U3P_SUCCESS => I'd expect CY_U3P_ERROR_FAILURE (acc. FX3APIGuide)
CyU3PI2cWaitForAck() returned CY_U3P_ERROR_TIMEOUT as expected
This is the according code-snippet:
=> the variable dmaUsb2CpuBuffer.buffer holds a valid address (pointing to a character) and dmaUsb2CpuBuffer.count  = 1!

i2cPreamble.buffer[0] = 0xB0;
i2cPreamble.ctrlMask = 0;
i2cPreamble.length = 1;
apiRetStatus = CyU3PI2cWaitForAck (&i2cPreamble, 3);    // repeat it 3 times if didn't got ACK
if(apiRetStatus == CY_U3P_SUCCESS)
{
    CyU3PDebugPrint (4, "CyU3PI2cWaitForAck() succeeded!\r\n");
}
else
{
    CyU3PDebugPrint (4, "CyU3PI2cWaitForAck() failed: %s\r\n", appGetErrorString(apiRetStatus));
}

// write preamble and data received from USB to I2C
apiRetStatus = CyU3PI2cTransmitBytes(&i2cPreamble, dmaUsb2CpuBuffer.buffer,
                                     dmaUsb2CpuBuffer.count, 0);
if (apiRetStatus == CY_U3P_SUCCESS)
{
    CyU3PDebugPrint (4, "CyU3PI2cTransmitBytes() succeeded!\r\n");
}
else
{
    CyU3PDebugPrint (4, "CyU3PI2cTransmitBytes() failed: %s\r\n", appGetErrorString(apiRetStatus));
}

Could you pls help me to get rid of this!
I'm using SKD Beta3.1 and FX3's Dvlp-board.

Thanks a lot!
Regards,
Robert

Please create a tech support case (MyAccount -> MyCases) with this information so that one of our engineers can interact with you and addressed your concerns in the right way.

Regards,

Anand

Hi Anand,

in the FX3-ReleaseNotes of SDK V1.0 I found the following known issues about I2C:

" 4. When there is a failure in an I2C transaction, the I2C block needs to be reset. This can be
done by invoking CyU3PI2cDeInit(), followed by a CyU3PI2cInit() and a
CyU3PI2cSetConfig().
5. A delay of about 5 ms is required between an I2C write operation and the next I2C
operation. "

Do you plan do fix this issues in near future?

Regards,
Robert

Just wanna share the research-results of the Cypress support-team and me:

1.) the I2C-1MHz-mode seem to work only after setting explicitely the I2C-drivestrength to CY_U3P_DS_FULL_STRENGTH

2.) using CyU3PI2cTransmitBytes() to send only 1 byte always returns CY_U3P_SUCCESS => this is a bug