CM-X300: WinCE: I2C Programming

Introduction

This sample application demonstrates the I2C communication with CAT9555 GPIO extender located on SB-X300. The CAT9555 datasheet is available at: 9555.pdf.

I2C Sample

The sample application performs the following actions:

• Read the configuration registers. Normal mode clock is used.
• Write registers. Set all pins, except for pin 0, to inputs.
• Read the registers to verify write.
• Read the output port register.
• Write the output port register. Configure pin 1 on P9 in the SB-X300 to be low.

Connecting Custom Device

I2C physical interface:

Signal Name	SB-X300	CM-X300
SCL	Pin 27 of connector P12	Pin 61 on the CAMI connector P1
SDA	Pin 26 of connector P12	Pin 60 on the CAMI connector P1

I2C Driver API

The Windows CE demo image includes an I2C driver that allows interaction with I2C devices. The I2C driver is a stream driver that may be accessed using the "I2C" prefix. The following pseudo code describes the driver’s algorithm:

1.  Set the clock speed according to mClkSpeed
2.  FOR i=0 TO i=mTransaction-1
      IF (mOpCode[i] == I2C_OPCODE_WRITE) THEN
         FOR j=0 TO mTransLen[i]-1   
           write mBuffer[mBufferOffset[i]+j] to the bus.
      ELSE IF (mOpCode[i] ==  I2C_OPCODE_READ) THEN 
         FOR j=0 TO mTransLen[i]-1
           read mTransLen[i] bytes from the bus into mBuffer[mBufferOffset[i]+j]
      ELSE “Fail – OpCode not supported”

Data Types

PXA_I2C_SPEED_T

Values

PXA_I2C_FAST_SPEED - use 400KHz clock

PXA_I2C_NORMAL_SPEED - use 100KHz clock

PXA_I2C_OPERATION_CODE

Values

I2C_OPCODE_READ

I2C_OPCODE_WRITE

I2CTRANS

Fields

Name	Description
DWORD mTransactions	Number f transactions to perform
PXA_I2C_SPEED_T mClkSpeed
UCHAR mDeviceAddr	7 bit I2C address
PXA_I2C_OPERATION_CODE *mOpCode
DWORD *mBufferOffset	The offset for the data in the array for each transaction
DWORD *mTransLen	The length of each transaction
DWORD mErrorCode
UCHAR *mBuffer	The buffer with the data for all the transactions

Functions

HANDLE I2CUserOpen()

Opens an instance of the I2C Driver.

Return Values

Returns a handle that should be used to access the driver. Nonzero indicates success.

void I2CUserClose(HANDLE hDevice)

Closes the driver handle

Parameters

• hDevice - Handle to an open driver instance

void I2CUserTransact(HANDLE hDevice, I2CTRANS* pTrans)

Perform the I2C transaction

Parameters

• hDevice - Handle to an open driver instance
• pTrans

Return Values

TRUE on success