Hi Chris,
I am using a KL17 and the I2C interface operates as slave.
I read the note about the TCF flag, but it lacks clarity. "during or immediately following" unfortunately does not give one much to go by. It just mentions the TCF bit is cleared when reading/writing the data register, but doesn't mention what else clears this bit. The fact that this flag is invalid when the ISR is finally fired does show this to be true of course, but the mechanism behind it is not clear. Regardless, I can't do much about that which is why I want to delay the following Stop bit and Start bit.
I am aware that the PIT ISR is quite lengthy, but the calculations have a strict time requirement, so I have yet to work out a work-around for this. Until I do, I'm stuck with it.
Which brings me to my actual issue, which is the FACK functionality. In my original post, I mentioned that there is no more respone after the 'manual' ACK. I also mentioned that in the idle state, I reset the FACK bit to '0', as to auto-acknowledge an addressmatch (because in the SMBUS spec, a slave always has to acknowledge addressing, I am however not implementing SMBUS, even though the FACK functionality seems to be meant for SMBUS).
This seemed a bit too complicated however, and upon examining the proposed flow chart for an SMBUS implementation (just to know how to use the FACK functionality), I see that an addressmatch is not auto-acknowledged, but just 'manually' acknowledged.
So I modified (simplified) my implementation to always leave the FACK bit at '1'. When I do this, I never receive any IRQ. Not even once. So even Start and Stop don't generate an IRQ.
Some details:
- the I2C is running on priority 0 (maximum), so the PIT cannot disturb it
- I'm using Kinetis Design Studio, provided by NXP
- When not setting the FACK bit to '1', I do get interrupts
The initialization of the module looks like this:
void init_IWF_I2C(void) {
i2c_slave_config_t I2C_slaveConfig;
I2C0->SMB |= 0x80; // Disable automatic ACK transmission to extend ACK or NACK
I2C_slaveConfig.addressingMode = kI2C_Address7bit;
I2C_slaveConfig.enableGeneralCall = false;
I2C_slaveConfig.enableWakeUp = false;
I2C_slaveConfig.enableHighDrive = false;
I2C_slaveConfig.enableBaudRateCtl = false;
I2C_slaveConfig.enableSlave = true;
I2C_slaveConfig.slaveAddress = 0x42;
I2C_SlaveInit(I2C0, &I2C_slaveConfig);
/* Enable I2C0 slave NVIC interrupt. */
NVIC_SetPriority(I2C0_IRQn, 0);
EnableIRQ(I2C0_IRQn);
I2C_EnableInterrupts(I2C0, kI2C_GlobalInterruptEnable | kI2C_StartStopDetectInterruptEnable);
}
The ISR starts like this:
void I2C0_IRQHandler(void) {
DEBUG_PIN_TOGGLE; // toggles oscilloscope C3
//... rest of ISR
}
I found no hint as to why interrupts would be absent hen enabling ('1') the FACK bit.
Edit: I forgot to mention that, on the oscilloscope, all I see now is Start -> address -> NACK -> Stop, and the DEBUG_IN remaining static all the time.
