No I2C communication with Nucleo-F411RE and ADXL345

[NicRoberts]

I used STM32CubeMX to set up a Nucleo board (STM32F411RE) to communicate via I2C with a ADXL345 accelerometer.

- RCC & clock settings at default

- SDA on PB9 and SCL on PB8

- I2C Fast Mode

- targeted MDK-ARM toolchain

- generated code

In `main.c` added the following code,

#define adxl_address 0x53<<1 // was told that this left shift was necessary for the HAL to fucntion properly??

uint8_t data_rec[6]; // data recieved in bytes
uint16_t x, y, z; // acc data

void adxl_write(uint8_t reg, uint8_t value)
{
uint8_t data[2];
data[0] = reg;
data[1] = value;
HAL_I2C_Master_Transmit(&hi2c1, adxl_address, data, 2, 10);
}

void adxl_read(uint8_t reg, uint8_t numberofbytes)
{
HAL_I2C_Mem_Read(&hi2c1, adxl_address, reg, 1, data_rec, numberofbytes, 100);
}

void adxl_init(void)
{
/* registers are all listed in adxl345 datasheet */
adxl_read(0x00, 1); // check if adxl is on line
adxl_write(0x2d, 0); // reset all bits
adxl_write(0x2d, 0x08); // measure bit-1, wakeup 0, 0 at 8hz
adxl_write(0x31, 0x01); // set range to +/- 4g
}

In `main()` I added the call to the adxl_init() function & in the main while loop,

  while (1)
  {
    /* USER CODE END WHILE */
    adxl_read(0x32, 6); // adxl output data register starts at 0x32
		x = (data_rec[1]<<8) | data_rec[0];
		y = (data_rec[3]<<8) | data_rec[2];
		z = (data_rec[5]<<8) | data_rec[4];
		
		HAL_Delay(10);
    /* USER CODE BEGIN 3 */
  }

I compile, all's fine, no errors, no warning. Download to the board, no issues. Open the debugger & run and get nothing! No values being read...

I've tried 2 different ADXL345s neither give any values.
ADXL set up the same as the pic below (R - 4k7)

Anyone see anything obvious?

EDIT:: I added a function to see if there was a device attached it comes up "NO" everytime

int ADXL345_ScanDeviceID()
{
	for(uint8_t address = 0; address < 255; address++)
	{
		if(HAL_I2C_IsDeviceReady(&hi2c1, address, 1, 100) == HAL_OK)
		{
			return address;
		}
	}
	return 0xff;
}

 EDIT 2:: I'm an ***, I had the wrong pins in the Nucleo board wired up!

[Andrew Neil]

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@NicRoberts wrote:

 EDIT 2:: I'm an ***, I had the wrong pins in the Nucleo board wired up!

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So is it working now?

[Tesla DeLorean]

>>I compile, all's fine, no errors, no warning.

Means its sufficiently syntatically correct, little else.

The errors returned by the function tell a more helpful story

The I2C addresses are 7-bit, not 8, and the 7-bits occupy the higher order bits, on the wire, and in the STM32

The low order bit is for read or write indication, so NOT 0 thru 255

int ADXL345_ScanDeviceID() // Will find first decoding part
{
	for(uint16_t address = 0; address < 128; address++)
	{
		if(HAL_I2C_IsDeviceReady(&hi2c1, address<<1, 1, 100) == HAL_OK)
		{
			return address;
		}
	}
	return 0xff;
}

[NicRoberts · Accepted solution]

Yes thanks, I had the wrong pins in the Nucleo board wired up and the problem was matching the Nulceo board breakout header pins with the MCU pins. In my case I needed access to PB8 & PB9 which are found on the Arduino header at D15 & D14 respectively.

[Andrew Neil]

Great - so please mark the solution:

https://community.st.com/t5/community-guidelines/help-others-to-solve-their-issues/ta-p/575256

[SofLit]

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@NicRoberts wrote:

Yes thanks (see OP for solution)

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Need to mark the comment that answered the question or at least guided you to the solution or add a comment where you give a solution or summarize it and accept it as solution. The goal is to make that solution visible so other community members can easily find it.

The solution is "I had the wrong pins in the Nucleo board wired up!" need to add that comment not to edit the original post and put it there. The solution is not visible for others.

Thank you for your understanding.

[NicRoberts]

OK done.