Electronic – STM32F415 weird I2C behaviour


I am using a STM32F415RGT6 embedded in the 1Bitsy Board. I want to set up the I2C Peripheral in order to read some data from a sensor. I am using the stm32f4 standard peripheral library.

My example code:

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE); 

GPIO_InitTypeDef gpioInit;


gpioInit.GPIO_Mode = GPIO_Mode_AF;

gpioInit.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;

gpioInit.GPIO_PuPd = GPIO_PuPd_UP;

gpioInit.GPIO_Speed = GPIO_Speed_25MHz; 

GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_I2C1); 

GPIO_Init(GPIOB, &gpioInit); 

RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1, ENABLE); 


I2C_InitTypeDef I2C_InitStructure;


/* I2C configuration */

I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;

I2C_InitStructure.I2C_ClockSpeed = 100000;

I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;

I2C_InitStructure.I2C_OwnAddress1 = 0x01;

I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;

I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;

I2C_Init(I2C1, &I2C_InitStructure);

I2C_Cmd(I2C1, ENABLE);

while (I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY));

/* Generate Start, send the address and wait for ACK */

I2C_GenerateSTART(I2C1, ENABLE);

while (!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));

I2C_Send7bitAddress(I2C1, 0xE0, I2C_Direction_Transmitter);


After that I want to write a 0x00, but the code always hangs in the last line, apparently the Master never reads the acknowledge. The I2C status registers always read:

I2C1 -> SR1 = 1024

I2C1 -> SR2 = 3

which means that the Acknowledge Failure bit is always set. If I analyze it using my Saleae I get the following:

STM32F415 Logic Analyzer

The Slave sends the ACK, but the STM32F415 cannot read it.

The weird thing: If I try the same code on my F407 – Disco (only with clock set to 400khz, but it's the same behaviour on both MCUs regardless of Speed), it works flawlessly:

STM32F407-DISCO Logic Analyzer

All other peripherals work fine. I already tried several workarounds, but the AF bit is always set, regardless of method. I hope you can help me.

P.S: I have tried with and without additional pullups and the I2C Slave Address is fine, because it works with STM32F0, STM32F4-DISCO and Atmel Mcus.

Best Regards and Thanks in advance!

Best Answer

thanks for all the suggestions. I found the solution and it's kind of weird. It works correctly on both boards, but on the STM32F415 it does not work with the logic analyzer capturing the data. On the F407 it does not matter. It's kind of a heisenbug, it does not happen if I don't look, but I had to look to know if it is working.

Related Topic