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Help needed with STM32 discovery and I2C

Question asked by delpu.gregory on Apr 12, 2011
Dear all,

My name is Gregory and I live in France (so excuse my poor english). I am a newbie in STM32 world, but I come from the Arduino world and have some good basis in C programing.

I try to use a DS1307 chip with my discovery board but I'm facing a problem for a few days now that I can't overcome.

Here below is the code of my main.c file, I try to read values in the RTC DS1307 chip, I sniff the I2C bus with a logic analyzer and I can clearly see the start command followed by the slave adresse + the direction bit and then a NACK, the chip is working (tested on my arduino board) and I can't understand why I get a NACK (I expect the slave to ACK and then send the bytes from the eeprom). Moreover, I never get the event EV6

I will be great if you can help me.

Code : 

#include "stm32f10x.h"

#define I2C_SPEED                     100000 /*!< I2C Speed */
#define I2C1_SLAVE_ADDRESS7          0b11010000
#define I2C_TIMEOUT                 100000

GPIO_InitTypeDef GPIO_InitStructureOutput; // Structure for Output Definitions
GPIO_InitTypeDef GPIO_InitStructureI2C; // Structure for I2C Definitions

I2C_InitTypeDef I2C_InitStructure; // Structure for I2

/* Private functions ---------------------------------------------------------*/

  * @brief  Main program
  * @param  None
  * @retval : None
int main(void)

       GPIO_InitTypeDef GPIO_InitStructure;
       I2C_InitTypeDef  I2C_InitStructure;
       int                   TimeOut;

       /* GPIOB Periph clock enable */
       RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

       /* I2C1 and I2C2 Periph clock enable */
       RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1, ENABLE);

       /* Configure I2C1 pins: SCL and SDA ----------------------------------------*/
       GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_6 | GPIO_Pin_7;
       GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
       GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_OD; // Open Drain, I2C bus pulled high externally
       GPIO_Init(GPIOB, &GPIO_InitStructure);

       /* Enable I2C1 -------------------------------------------------------------*/

       I2C_Cmd(I2C1, ENABLE);

       /* I2C1 configuration ------------------------------------------------------*/
       I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;
       I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;
       I2C_InitStructure.I2C_OwnAddress1 = 0x039;
       I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;
       I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;
       I2C_InitStructure.I2C_ClockSpeed = I2C_SPEED;
       I2C_Init(I2C1, &I2C_InitStructure);

       /*----- Transmission Phase -----*/

       /* Send I2C1 START condition */
       I2C_GenerateSTART(I2C1, ENABLE);

       /* Test on I2C1 EV5 and clear it */
       TimeOut = I2C_TIMEOUT;
       while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT))
            if (TimeOut == 0) return 1;

       I2C_SendData(I2C1, 0x00); // Send Year register address

       /* Send DS1307 slave Address for write */
       I2C_Send7bitAddress(I2C1, I2C1_SLAVE_ADDRESS7, I2C_Direction_Transmitter);

        //Test on I2C1 EV6 and clear it
       TimeOut = I2C_TIMEOUT;
            if (TimeOut == 0){
                 // Send I2C1 STOP Condition
                 I2C_GenerateSTOP(I2C1, ENABLE);

                 return 2;

       return 1;