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Level 2
Level 2
Dear support,

I would really need support with the I2C-bus.

Have a system with XMC4500 up and running, it can operate for several weeks until suddenly the I2C-bus stops responding.

The XMC4500 is master, and have two slave pheriperals: a IO-expander and a RTC.

It uses I2C001-app 1.0.28 with FIFO buffers for both RX and TX.
I queue up all TDF-codes and data to the FIFO. The interrupt handler counts ack-interrupts and sets a semaphore when the stop condition is transfeered. I can therefore verify a successful write without doing "busy wait".

It works great until a fault conditon occurs. I have in the past already implemented a fail recovery mechanism which is called once before i issue a new I2C start condition:

if(I2C001_Handle0.I2CRegs->TCSR & USIC_CH_TCSR_TDV_Msk){
//Recover from an error state

I2C001_Handle0.I2CRegs->PSCR |= 0x3FF;

// Flush FIFO buffer

// Modify Transmit Data Valid
I2C001_Handle0.I2CRegs->FMR |= (((uint32_t) 2) << USIC_CH_FMR_MTDV_Pos) & USIC_CH_FMR_MTDV_Msk;

This has proven to not be sufficient - the I2C-bus still stays in a non responding state.

Have read the reference manual, and I belive that it must be due to out of synch with one of the pheriperals. Maybe the bus has switched direction, and the
bus is not idle once i issue a new start condition. It can also be out of synch with the state machine of the pheriperal - the TDF-code is not accepted at the current state.

But how do i recover from this state? By the reference manual it seems like i need to act different depending on current state. But this is quite complicated when using a FIFO - What command did it go wrong? How to react? ...

Isn't there a fool-prof way of resetting the bus forceing it back to idle?
1 Reply
Hi Andersr,

Do you have an I2C bus analyzer? I would recommend that you use an I2C bus analyzer to better understand what is going on with the I2C bus when the failure case occurs. If one of the I2C slaves is hanging up the bus, then you may need a way to reset the slave device.

I use a Logic 8 I2C bus analyzer from Saleae: https://www.saleae.com/ and it is very helpful for understanding and resolving I2C bus communications.