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Hello,

I'm working on an application that will use the PCA9536 I2C i/o expander. It seems pretty straightforward, but all of the I2C transactions are timing out. This is the first time I've used the I2C library, so I could be missing something basic. The outline of what I'm doing and the code for reading and writing is shown below. If anyone can comment on what I might be doing wrong, I'd appreciate it. The status value returned by all of the I2C functions is 4 (I2C_TIMEOUT).

Joe


Platform is SB70LC.
Pins[16].function( PIN16_SDA )
Pins[17].function( PIN17_SCL )
7-bit I2C address is 65.
#include <i2cmaster.h>
I2CInit() is called before any other I2C function.
Write to DIRECTION register (3) to set i/o function.
Write to OUTPUT register (1) to set output values.
Read from INPUT register (0) to read input values.

BYTE PCA9536_GetRegister( BYTE regnum )
{
BYTE data = 0;

int status;
status = I2CStart( 65, I2C_START_WRITE );
status = I2CSend( regnum );
status = I2CRestart( 65, I2C_START_READ );
status = I2CRead( &data );
I2CStop();

return data;
}

void PCA9536_SetRegister( BYTE regnum, BYTE data )
{
int status;
status = I2CStart( 65, I2C_START_WRITE );
status = I2CSend( regnum );
status = I2CSend( data );
I2CStop();
}

I was able to get the driver for PCA9536 working by using what NB calls the simple I2C functions rather than the advanced ones. I don't know what I was doing wrong with the advanced functions, which seem pretty straightforward, but I guess that's why they provide the simple ones. Thanks, NB. Note that I2CInit() must be called before calling any other I2C function.

Joe

One note about using NB's standard RTC with the SB70LC. Our board has both the PCA9536 i/o expander and also the NB standard PCF8563 real-time clock. For some reason, the RTC module is not included in the SB70LC library. I simply copied system/rtc.cpp and include/rtc.h from the MOD5270 folder to my project folder, added #include <rtc.h> in main.cpp, and it builds and runs fine.

Joe