Hello,

I've been trying to set up 2 BGM13P32 on development boards with an I2C communication, where one would act as a master and the other one as a slave.

I did try to check what is the outcome on a Oscilloscope. I noticed that the integrated pull-ups are very weak and I did my own pull-ups just to see what would happen. The behavior stays the same but the signals are much more square.

Though, either the master keeps the SDA line low or the slave keeps the clock low for an indefinite amount of time after ACKing the address by the slave, which sometimes cause an Arbitration lost by the master and other times, it is just an undefined behavior of the I2C protocol.

Here is a code sample of what I have right now (yes it was taken from a few tutorials and forum questions because nothing was working as expected) : 

static volatile bool transmitting = false;

void I2C0_IRQHandler(void)
{
	uint32_t status = I2C0->IF;

	if (status & I2C_IF_ADDR){ // Receiving Address
		uint8_t addr;
		addr = I2C0->RXDATA;
		I2C_IntClear(I2C0, I2C_IFC_ADDR);

		if (addr & 0x01) { // 0x01 is the read bit
			I2C0->TXDATA = (uint32_t) tx_callback();
			transmitting = true;
		}
	} else if (status & I2C_IF_RXDATAV) { // Receiving data
		rx_callback(I2C0->RXDATA);
	} else if (status & I2C_IF_ACK) { // Ack from master after first byte of data sent
		if (transmitting) {
			I2C0->TXDATA = (uint32_t) tx_callback();
		}
		I2C_IntClear(I2C0, I2C_IEN_ACK);
	} else if (status & I2C_IF_NACK) { // Master Nack, stop sending data
		if (transmitting) {
			transmitting = false;
		}
		I2C_IntClear(I2C0, I2C_IFC_NACK);
	}
	if (status & I2C_IEN_SSTOP) { // Stop transfer
		I2C_IntClear(I2C0, I2C_IFC_SSTOP);
	}
}

void enableI2cSlaveInterrupts(void){
  I2C_IntClear(I2C0, I2C_IEN_ADDR | I2C_IEN_RXDATAV | I2C_IEN_SSTOP);
  I2C_IntEnable(I2C0, I2C_IEN_ADDR | I2C_IEN_RXDATAV | I2C_IEN_SSTOP);
  NVIC_EnableIRQ(I2C0_IRQn);
}

void setup_i2c(bool is_master) {
	// Set up SCL and SDA
	I2C0->ROUTEPEN = I2C_ROUTEPEN_SCLPEN | I2C_ROUTEPEN_SDAPEN;
	I2C0->ROUTELOC0 = (I2C0->ROUTELOC0 & (~_I2C_ROUTELOC0_SCLLOC_MASK)) | I2C_ROUTELOC0_SCLLOC_LOC15;
	I2C0->ROUTELOC0 = (I2C0->ROUTELOC0 & (~_I2C_ROUTELOC0_SDALOC_MASK)) | I2C_ROUTELOC0_SDALOC_LOC15;

    // Remove PullUp configuration and add own pull-ups
	GPIO_PinModeSet(BSP_I2C0_SCL_PORT, BSP_I2C0_SCL_PIN, gpioModeWiredAndPullUpFilter, 1); 
	GPIO_PinModeSet(BSP_I2C0_SDA_PORT, BSP_I2C0_SDA_PIN, gpioModeWiredAndPullUpFilter, 1);

	if (is_master) {
		for (unsigned int i = 0; i < 9; i++) {
			GPIO_PinOutSet(BSP_I2C0_SCL_PORT, BSP_I2C0_SCL_PIN);
			GPIO_PinOutClear(BSP_I2C0_SCL_PORT, BSP_I2C0_SCL_PIN);
		}
	}

	I2C_Init_TypeDef i2c_configuration = I2C_INIT_DEFAULT;
	i2c_configuration.master = is_master;

	I2C_Init(I2C0, &i2c_configuration);

	if (!is_master) {
		I2C0->SADDR = SLAVE_ADDRESS;
		I2C0->CTRL |= I2C_CTRL_SLAVE | I2C_CTRL_AUTOACK | I2C_CTRL_AUTOSN;
		enableI2cSlaveInterrupts();
	}
}

int main(void)
{
	/* Initialize device */
	initMcu();
	/* Initialize board */
	initBoard();

	app_init();

	setup_i2c(MASTER_NODE);

	if (MASTER_NODE) {
		printf("Master \n");
		uint8_t data[1];
		I2C_TransferSeq_TypeDef seq ={
				.addr = SLAVE_ADDRESS,
				.buf[0].data = data,
				.buf[0].len = 1,
				.flags = I2C_FLAG_READ
		};

		I2C_TransferReturn_TypeDef status;
		status= I2C_TransferInit(I2C0, &seq);

		while (status == i2cTransferInProgress){
			status = I2C_Transfer(I2C0);
		}

		printf("Sent and received : %d with status : %d \n", seq.buf[0].data[0], status);
	} else {
		printf("Slave \n");
		data_buffer[0] = 0x7F;
	}

	while (1) {

	}
}

// In app_init()
CMU_ClockEnable(cmuClock_HFPER, true);
CMU_ClockEnable(cmuClock_GPIO, true);
CMU_ClockEnable(cmuClock_I2C0, true);
RETARGET_SerialInit();

It might be my configuration that is not adequate. At this point, I cannot figure out if it is a hardware or software problem.

Thank you for your time!