To read two sensor values with i2c

[ark2]

I'm trying to get the sensor value with stm32

Maybe because I connected the board to one i2c and attached two sensors, the value didn't change

Most people use cereal, but I only use C, so I have to use HAL

The sensor that allows you to read only one is HTU21

I'm doing this and that, but I only got 01 00 00 00 00

I think I didn't code properly, but I don't know where to fix it

I want to get the sensor value and use it as a hex value and float value, so please tell me how

uint8_t hum_addr = 0x40;
   uint8_t hum_sec_addr = 0xE5;  
   uint8_t buf[5] = {0x01, 0x00 }; 
   uint8_t R_buffer1[5] = {0x01, 0x00 }; 
   uint8_t R_buffer2[5] = {0x00, 0x00 };  
   HAL_StatusTypeDef ret;
 
//ret = HAL_I2C_Master_Transmit_IT(&hi2c1, (uint16_t)hum_addr, (uint8_t*)R_buffer1, 2);    
    //ret = HAL_I2C_Master_Receive_IT(&hi2c1, (uint16_t)hum_addr, (uint8_t*)R_buffer2, 2);
    ret = HAL_I2C_Mem_Read_IT(&hi2c1, (uint16_t)(hum_addr << 1), hum_sec_addr, 1, R_buffer2, 5);
      for(int i = 0; i < 5; i++){
        printf("%02X ", R_buffer2[i]);
      }
        printf("\n\r");

Humidity sensor datasheet

http://dlnmh9ip6v2uc.cloudfront.net/datasheets/BreakoutBoards/HTU21D.pdf

Humidity sensors are connected to SD0, SC1 via i2c

[Foued_KH]

Hello @ark​,

I suggest you try to use the I2C sensor address without shift:

HAL_I2C_Mem_Read_IT(&hi2c1, (uint16_t) hum_addr , hum_sec_addr, 1, R_buffer2, 5);

Hope my answer helped you!

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Foued

[Tesla DeLorean]

0xE5 doesn't seem like it can be a valid address.

[Foued_KH]

It's a measurement command (Temperature) for the read.

Foued

[S.Ma]

Take an oscilloscope (not a logic analyser guys) and observe the i2c bus. Monitor the slave address ack bit.

[raptorhal2]

The code doesn't appear to provide the 7 to 50 msec Hold during measurement. See page 5 of the data sheet.

(Edit) You might try asking for example code as stated on data sheet page 10. The data sheet date is 9 years ago, so there may be no response.