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ST HAL I2C generating wrong address.

Question asked by jcastells on Feb 12, 2016
Latest reply on Feb 15, 2016 by Clive One
Hello,

I've been working with ST HAL libraries for an STM32F030R8T6, using the NUCLEO board, and I'm having some problems with the I2C API. Probably it's a configuration issue but for the love of me, I can't find it.

The problem:
I call the function HAL_I2C_Master_Transmit_XX with address 0x3E. I attach a logic analyzer to the output to check the lines, and the address does not match. The address I see on the line is 0x1F.

My main test code is the following. (Just to reproduce this situation) It is a direct copy from the NUCLEO examples.
I skip over the SystemClock_Config and MspInit, since I can see data on the lines (I2C is sending data correcly) and they don't provide information for my current problem.
01.#define I2C_ADDRESS        0x3E
02.#define I2C_TIMING      0x00A51314
03.uint8_t bTransferRequest = 0;
04. 
05.//(other stuff)
06. 
07.int main(void)
08.{
09.  HAL_Init();
10.   
11.  /* Configure the system clock to 48 MHz */
12.  SystemClock_Config();
13.   
14.  /*##-1- Configure the I2C peripheral ######################################*/
15.  I2cHandle.Instance             = I2C1;
16. 
17.  I2cHandle.Init.Timing                      = I2C_TIMING;
18.  I2cHandle.Init.OwnAddress1           = I2C_ADDRESS;
19.  I2cHandle.Init.AddressingMode     = I2C_ADDRESSINGMODE_7BIT;
20.  I2cHandle.Init.DualAddressMode   = I2C_DUALADDRESS_DISABLE;
21.  I2cHandle.Init.OwnAddress2           = 0xFF;
22.  I2cHandle.Init.GeneralCallMode     = I2C_GENERALCALL_DISABLE;
23.  I2cHandle.Init.NoStretchMode        = I2C_NOSTRETCH_DISABLE; 
24.   
25.  if(HAL_I2C_Init(&I2cHandle) != HAL_OK)
26.  {
27.    /* Initialization Error */
28.    Error_Handler();
29.  }
30. 
31.  /* Enable the Analog I2C Filter */
32.  HAL_I2CEx_ConfigAnalogFilter(&I2cHandle,I2C_ANALOGFILTER_ENABLE);
33. 
34. 
35.  while(1){
36.      HAL_I2C_Master_Transmit(&I2cHandle, (uint16_t)I2C_ADDRESS, (uint8_t*)&bTransferRequest, 1, 1000);
37.      HAL_Delay(1000);
38.  }
39. 
40.return 0;
41.}

This code, when examining the output with the logic analyzer, generates the following SDA/SCL sequence.

LA_I2C_Capture.PNG

The Theory:
I went down to the ST code generating the address.
/*******************************************************************************
  * @file    stm32f0xx_hal_i2c.c
  * @author  MCD Application Team
  * @version V1.3.0
  * @date    26-June-2015
 ******************************************************************************/
//(etc)
 
static void I2C_TransferConfig(I2C_HandleTypeDef *hi2c,  uint16_t DevAddress, uint8_t Size, uint32_t Mode, uint32_t Request){
//(etc)
  /* update tmpreg */
  tmpreg |= (uint32_t)(((uint32_t)DevAddress & I2C_CR2_SADD) | (((uint32_t)Size << 16 ) & I2C_CR2_NBYTES) | \
            (uint32_t)Mode | (uint32_t)Request);
 
  /* update CR2 register */
  hi2c->Instance->CR2 = tmpreg;

And from the reference manual for STM32F0 devices, section 25.7.2, Control Register 2 (I2C_CR2):
Bits 9:8 SADD[9:8]: Slave address bit 9:8 (master mode)
    This bit are don’t care
Bits 7:1 SADD[7:1]: Slave address bit 7:1 (master mode)
    These bits should be written with the 7-bit slave address to be sent
Bit 0 SADD0: Slave address bit 0 (master mode)
    This bit is don’t care

I understand that on 7 bit address mode, the CR2 bits used to generate the address are SADD[7:1] neglecting the value of SADD0. But the ST HAL driver seems to write the value directly (with no shifting at all),
hence the "transformation" from 0x3E to 0x1F:
I2C_CR2[7:0] = 0x3E
I2C_CR2[7:1] = 0x1F
This would be fine for 10 bit addresses, but I'm having trouble with 7 bit.

I tested using an I2C temperature sensor (address 0x40). And I can't read anything at all using 0x40, but everything is fine and dandy when using 0x80.

Could somebody please point me to any configuration flag that I may have missed?

Salut!

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