Anat Ruangrassamee

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8 years, 11 months ago.

HDC1000 with Nucleo 401RE

Hello

I am using the HDC1000 temp sensor by ControlEverything with the Nucleo 401RE. https://shop.controleverything.com/products/humidity-and-temperature-sensor-3-rh-0-2-c

I tried to review some information on I²C and HDC1000 for mbed is here

https://developer.mbed.org/handbook/I2C https://developer.mbed.org/users/kenjiArai/code/HDC1000/ https://developer.mbed.org/users/yasuyuki/code/mbed_HDC1000/

I used the following code but I got the temp = -39.88 C. What was wrong in my code? Thanks.

my code

#include "mbed.h"
 
// Read temperature 
 
I2C I²C (PB_9, PB_8);  //for STM32F401RE
 
const int addr = 0x40;
 
Serial pc(USBTX, USBRX);
 
int main() {
    char cmd[2];
    pc.baud(9600);
    
    while (1) {
        cmd[0] = 0x02;
        cmd[1] = 0x30;
        I²C .write(addr, cmd, 2);
 
        wait(0.5);
 
        cmd[0] = 0x00;
        I²C .write(addr, cmd, 2);
        
        wait(1.0);
        
        I²C .read(addr, cmd, 2);
 
        float tmp = (float((cmd[0]<<8)|cmd[1]));
        float cTemp = (tmp / 65536.0) * 165.0 - 40;
        pc.printf("Temp = %.2f deg C\n", cTemp);
        
    }
}

Anat,

Do you have pull up resistors on both i2c lines? values from 1.5k to 10k probably will do! :)

Regards,

Andrea, team mbed

posted by Andrea Corrado 06 Jun 2017

Thank you. After changing the address from 0x40 to 0x80, it works! The issue was about the 7-bit vs 8-bit address.

posted by Anat Ruangrassamee 06 Jun 2017
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