Introduction

As mentioned in the Device specific interface layout section of the Impact Acquire API manuals, the "I2CControl" is a feature which allows the mvBlueFOX device to communicate with custom-specific peripherals via the I2C interface.

Setting up the device

The following steps will explain how to connect the mvBlueFOX with an I2C device. In this use case, a LM75 I2C Digital Temperature Sensor is used:

Figure 1: ImpactControlCenter - I2C Interface Control

Start ImpactControlCenter
Initialize the mvBlueFOX device
Navigate to "Digital I/O -> I2CControl"
Enter the connection settings to address the I2C device memory (4).
E.g. to read the temperature of the example sensor, set I2CDeviceAddress to "0x09F".
Set I2CDeviceSubAddress to "0x00", because reading the temperature of this sensor does not need a sub address.
Set I2CBufferLength (5) to 2, because this sensor stores the temperature in a register of two bytes length.
Set the I2COperationMode (1) to Read. The least significant bit (LSB) of the device address will automatically be overwritten by 0 for writing and by 1 for reading.
Navigate to the int I2COperationExecute( void ) function (2). Click on the 3 dots next to the function name or right-click on the command and then select Execute from the context menu to send the current message to the I2C device.
The I2COperationStatus property (3) will display if the operation was successful.
On success, the data is now displayed in the I2CBuffer property (5). This value is a hexadecimal number and needs to be interpreted depending on the I2C device.

Note

The following I2C addresses will be blocked for access from an application:

i2c address range	affected devices
0x20-0x3F	all mvBlueFOX devices
0x66-0x67	all mvBlueFOX devices
0x90-0x91	mvBlueFOX-200w only
0xA0-0xA3	all mvBlueFOX devices
0xA6-0xA7	all mvBlueFOX devices
0xBA-0xBB	mvBlueFOX-202a and mvBlueFOX-205 only

Programming the I2C interface

The following lines of source code are meant to give an overview of the possibilities of the I2CControl class.

I2CControl i2cc( pBF ); // assuming 'pBF' to be a valid 'Device*' instance to an mvBlueFOX device
if( i2cc.I2COperationMode.isValid() )
{
  // direct property access
  i2cc.I2CBufferLength.write( 0 );
  i2cc.I2COperationMode.write( I2ComRead );
  assert( ( i2cc.I2COperationExecute.call() == DMR_INVALID_PARAMETER ) && "Unexpected driver behaviour" );
  assert( ( i2cc.I2COperationStatus.read() == I2CosNotEnoughData ) && "Unexpected driver behaviour" );
  i2cc.I2CBufferLength.write( 1 );
  // assuming we write to an invalid address
  assert( ( i2cc.I2COperationExecute.call() == DMR_EXECUTION_FAILED ) && "Unexpected driver behaviour" );
  assert( ( i2cc.I2COperationStatus.read() == I2CosFailure ) && "Unexpected driver behaviour" );
  i2cc.I2COperationMode.write( I2ComWrite );
  i2cc.I2CBuffer.writeBinary( string() );
  assert( ( i2cc.I2COperationExecute.call() == DMR_INVALID_PARAMETER ) && "Unexpected driver behaviour" );
  assert( ( i2cc.I2COperationStatus.read() == I2CosNotEnoughData ) && "Unexpected driver behaviour" );
  {
    char binData[2] = { 'A', 'B' };
    i2cc.I2CBuffer.writeBinary( string(binData, sizeof(binData)) );
  }
  // assuming we write to an invalid address
  assert( ( i2cc.I2COperationExecute.call() == DMR_EXECUTION_FAILED ) && "Unexpected driver behaviour" );
  assert( ( i2cc.I2COperationStatus.read() == I2CosFailure ) && "Unexpected driver behaviour" );
  // Write some data. This will only work if several conditions are met:
  // - there is a device that can be written to at address 0xA6
  // - the sub-address 0x04 is valid
  // - the device is designed to work with 8 bit sub-addresses
  // - the device can deal with 9 bytes in a single command
  i2cc.I2CDeviceAddress.write( 0xA6 );
  i2cc.I2CDeviceSubAddress.write( 0x04 );
  i2cc.I2CDeviceSubAddressWidth.write( 8 );
  {
    char binData[9] = { 'D', 'E', 'A', 'D', ' ', 'B', 'E', 'E', 'F' };
    i2cc.I2CBuffer.writeBinary( string( binData, sizeof( binData ) ) );
  }
  i2cc.I2COperationMode.write( I2ComWrite );
  int I2COperationExecuteResult = i2cc.I2COperationExecute.call();
  if( I2COperationExecuteResult != DMR_NO_ERROR )
  {
    printf( "'I2COperationExecute' write failed. Return value: %s(%d).\n", ImpactAcquireException::getErrorCodeAsString( I2COperationExecuteResult ).c_str(), I2COperationExecuteResult );
  }
  printf( "'I2COperationStatus' after write: %s.\n", i2cc.I2COperationStatus.readS().c_str() );
  // Read some data. Similar condition as for write apply
  const int bytesToRead = 4;
  i2cc.I2CDeviceAddress.write( 0xA8 );
  i2cc.I2CDeviceSubAddress.write( 0x00 );
  i2cc.I2CDeviceSubAddressWidth.write( 8 );
  i2cc.I2CBufferLength.write( bytesToRead ); // read 'bytesToRead' bytes
  i2cc.I2COperationMode.write( I2ComRead );
  i2cc.I2COperationExecute.call();
  I2COperationExecuteResult = i2cc.I2COperationExecute.call();
  if( I2COperationExecuteResult != DMR_NO_ERROR )
  {
    printf( "'I2COperationExecute' read failed. Return value: %s(%d).\n", ImpactAcquireException::getErrorCodeAsString( I2COperationExecuteResult ).c_str(), I2COperationExecuteResult );
  }
  printf( "'I2COperationStatus' after read: %s.\n", i2cc.I2COperationStatus.readS().c_str() );
  if( i2cc.I2CBuffer.binaryDataBufferSize() != bytesToRead )
  {
    printf( "'I2CBuffer' reports %d bytes of data while %d bytes where expected.\n", i2cc.I2CBuffer.binaryDataBufferSize(), bytesToRead );
  }
  // usage of the convenience functions
  i2cc.I2CWrite( 0xA4, 0x00, 8, string("TEST") );
  const string i2cReadBuffer = i2cc.I2CRead( 0xA4, 0x00, 8, 4 );
}
else
{
  printf( "I2CControl not available.\n" );
}