static extern int ExternalIoCtl(int fd, uint request, ref i2c_rdwr_ioctl_data xfer);
/// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
/// <summary>
/// Writes/Reads a buffer in from an I2C slave device using I2C_RDWR function.
///
/// </summary>
/// <param name="devID">The I2C Device ID to write to</param>
/// <param name="txByteBuf">The buffer with bytes to write, can be null for read only</param>
/// <param name="txBytes">The number of bytes to write, can be 0 for read only
/// <param name="rxByteBuf">The buffer with bytes to read, can be null for write only</param>
/// <param name="rxBytes">The number of bytes to read, can be 0 for write only
/// <history>
/// 19 Dec 18 Ridler - Originally written
/// </history>
public void I2CTransfer(int devID, byte[] txByteBuf, int txBytes, byte[] rxByteBuf, int rxBytes)
{
int ioctlRetVal = -1;
if (i2CPortFD <= 0)
{
throw new Exception("I2C port is not open, fd=0");
}
if (PortIsOpen == false)
{
throw new Exception("I2C port is not open");
}
i2c_msg[] msgs = new i2c_msg[2];
uint nmsgs = 0;
IntPtr txBufPtr = IntPtr.Zero;
IntPtr rxBufPtr = IntPtr.Zero;
if (txByteBuf != null && txBytes != 0)
{
txBufPtr = Marshal.AllocHGlobal(txBytes + 1);
// copy the data from the tx buffer to our pointer
Marshal.Copy(txByteBuf, 0, txBufPtr, txBytes);
msgs[nmsgs].addr = (UInt16)devID;
msgs[nmsgs].flags = 0;
msgs[nmsgs].len = (UInt16)txBytes;
msgs[nmsgs].buf = txBufPtr;
nmsgs++;
}
if (rxByteBuf != null && rxBytes != 0)
{
rxBufPtr = Marshal.AllocHGlobal(rxBytes + 1);
msgs[nmsgs].addr = (UInt16)devID;
msgs[nmsgs].flags = 1; // I2C_M_RD;
msgs[nmsgs].len = (UInt16)rxBytes;
msgs[nmsgs].buf = rxBufPtr;
nmsgs++;
}
// interpret it as an input error if nothing has to be done
if (nmsgs == 0)
{
throw new Exception("I2CTransfer on I2C device " + devID.ToString() + " has nothing to write or read!");
}
int msg_size = Marshal.SizeOf(typeof(i2c_msg)); // should be 12....
IntPtr msgbuffer = Marshal.AllocHGlobal(msg_size * 2);
IntPtr ptr = msgbuffer;
for (uint ndx = 0; ndx < nmsgs; ndx++)
{
Marshal.StructureToPtr(msgs[ndx], ptr, false);
ptr += msg_size;
}
i2c_rdwr_ioctl_data i2c_data = new i2c_rdwr_ioctl_data();
i2c_data.msgs = msgbuffer;
i2c_data.nmsgs = nmsgs;
try
{ ioctlRetVal = ExternalIoCtl(i2CPortFD, I2C_RDWR, ref i2c_data);
if (ioctlRetVal < 0)
{ // it failed
throw new Exception("ExternalIoCtl on I2C device " + devID.ToString() + " failed. retval=" + ioctlRetVal.ToString());
}
// did the caller supply a receive buffer
if (rxByteBuf != null)
{ // yes they did, copy the returned data in
Marshal.Copy(rxBufPtr, rxByteBuf, 0, rxBytes);
}
}
finally
{ if (txBufPtr != IntPtr.Zero)
{
Marshal.FreeHGlobal(txBufPtr);
}
if (rxBufPtr != IntPtr.Zero)
{
Marshal.FreeHGlobal(rxBufPtr);
}
Marshal.FreeHGlobal(msgbuffer); }
}