TWI is not working with SoftDevice

[diode]

This seems to be a common problem after searching in this forum. In my case, I need to read from an I2C slave and send the data out in BLE. I have made it work without SoftDevice using this library code http://pastebin.com/qLLAy418 . However, it failed to work with SoftDevice. I also tried with another version which has SoftDevice knobs http://pastebin.com/AV6cQK0x. It doesn't work either. I also tried other code github.com/.../twi_hw_master.c that someone claimed to work (devzone.nordicsemi.com/.../), but it doesn't work for me. Can anyone provide any suggestion on this problem?

[RK]

What does 'doesn't work' mean? Crashes, sends erratically, goes to the hardfault handler, the board bursts into flames, what?

The TWI handler in the library works with the softdevice quite happily, as it should, they are entirely separate things.

So what exactly happens when you use the nordic TWI driver from the SDK for your board with and without the softdevice?

[diode]

I used two versions of TWI drivers from nRF51 SDK8.0.0. One is "twi_sw_master.c", and the other is "twi_hw_master.c". For "twi_sw_master.c", when I read it from an I2C slave (with SoftDevice), the code got stopped the while (TWI_SCL_READ() == 0) line in this function:

static bool twi_master_wait_while_scl_low(void)
{
#if TWI_MASTER_TIMEOUT_COUNTER_LOAD_VALUE != 0
    uint32_t volatile timeout_counter = TWI_MASTER_TIMEOUT_COUNTER_LOAD_VALUE;
#endif
    // Pull SCL high just in case if something left it low
    TWI_SCL_HIGH();
    TWI_DELAY();
    while (TWI_SCL_READ() == 0)
    {.....}
}

I can set TWI_MASTER_TIMEOUT_COUNTER_LOAD_VALUE to nonzero value to avoid this, but return status is not success. For "twi_hw_master.c", read will just return false.

If you have a working TWI example with SoftDevice, could you please share?