I2C Slave on startkit

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I2C Slave on startkit

Postby Folknology » Tue Jul 15, 2014 12:25 pm

I need to do some I2C control work that involves the XMOS side to operate in slave mode (It's externally operated and configured via I2C). So I figured I would play around with the I2C_Module part of SC_I2C in github xcore.

I took my prompt from the XDK test app which uses this module to create master and slave for testing, here is the code I used:

Code: Select all

#include <xs1.h>
#include <i2c.h>
#include <xscope.h>
#include <print.h>
struct r_i2c i2c_slave  = { XS1_PORT_1E, XS1_PORT_1F };
struct r_i2c i2c_master  = { XS1_PORT_1G, XS1_PORT_1H };
struct i2c_data_info i2c_slave_data, i2c_master_data;
int main(void) {
  i2c_master_init(i2c_master); // not actually needed
  par {
  return 0;

static void i2c_tx(){
  unsigned int ret_ms;

  i2c_master_data.data_len = 5;
  i2c_master_data.data[0] = 0x81;
  i2c_master_data.data[1] = 0x40;
  i2c_master_data.data[2] = 0x81;
  i2c_master_data.data[3] = 0xA1;
  i2c_master_data.data[4] = 0x55;
  i2c_master_data.clock_mul = 1;
  ret_ms = i2c_master_tx(0x10, 0x06,i2c_master_data,i2c_master);
  printstr("Master return = ");

static void i2c_rx(){
  unsigned int ret_sl;

  ret_sl = i2c_slave_rx(0x10,i2c_slave_data,i2c_slave);
  printstr("Slave return = ");
  if(ret_sl) {
    printstr("Data Len = ");
    printstr("Data = ");
    for(int i=0; i < i2c_slave_data.data_len; i++ ) {

My Makefile file includes only the I2C_Module.

When I run this I get (what I presume are) ACK failures:

Code: Select all

awood@Al:~/xcorelibs/winder$ xrun --xscope-io-only bin/Winder.xe Starting
Slave return = 0
Master return = 0
I am connecting 1F->1H and 1E->1G and have added 2 external pull up resistors to +3v3

It may be I am missing something, I have little I2C slave experience , any ideas?

I am wondering if this module is actually up to date as I also found this I2C tutorial which has this rather ominous comment at the bottom:
Known issues

This project was made during my spare time as a submission for the XCore github challenge

Only seems to work with 10.4.2 tools, this is to do with the sc_i2c package which also fails to run under 11.2 and higher (or at least in my attempts it did). I have submitted a bug report for this.
I also seem to remember something about the I2C_Module being deprecated into separate Master/Slave modules.

Thus I would like to know if the I2C_module is no longer supported or is it planned to be fixed.

Is there an alternate Slave implementation that does work

And can we get the sc_I2C library sorted out, it's as confusing as hell to me

Any help appreciated....


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