I2C interface with HTU21D using nrf51822

RE: I2C interface with HTU21D using nrf51822

au — Wed, 21 Mar 2018 13:48:45 GMT

I think for reading temperature with no hold the correct address is 0xF3 instead of 0xE3:

uint8_t trigger_temperature_no_hold_master = 0xF3; //Address to temperature reading with no hold of twi lines

instead of:

uint8_t trigger_temperature_no_hold_master = 0xE3; //Address to temperature reading with no hold of twi lines

RE: I2C interface with HTU21D using nrf51822

samchang — Wed, 05 Oct 2016 12:30:20 GMT

Hello ,thanks for the examples. when I using in this example,the values (humidity or temperature)is correct initially in a small period of time (various about 3~10 minutes) after that ,the values might change to humidty -6, temperature -46 ,I wonder to kown there is the problem ?? Thanks!

RE: I2C interface with HTU21D using nrf51822

rushin — Wed, 27 Jan 2016 15:16:05 GMT

i used my humidity function. now its working. thanks for your help

RE: I2C interface with HTU21D using nrf51822

rushin — Wed, 27 Jan 2016 15:13:59 GMT

what to write in main??

RE: I2C interface with HTU21D using nrf51822

Fredrik Sundt Brynhildsvoll — Wed, 27 Jan 2016 15:10:03 GMT

Great, then we have one less problem. I might have a solution. I have edited the code above a bit by adding a short delay after receiving the bytes from the humidity sensor. I have previously experienced that this is needed. Could you try the above code? And can you add the code (from main) where you call these functions?

RE: I2C interface with HTU21D using nrf51822

rushin — Wed, 27 Jan 2016 14:39:57 GMT

your temperature function is working. giving me 28 degree. but humidity function is not working

RE: I2C interface with HTU21D using nrf51822

Fredrik Sundt Brynhildsvoll — Wed, 27 Jan 2016 14:29:01 GMT

Is the humidity and temperature changing or are they constant?

RE: I2C interface with HTU21D using nrf51822

rushin — Wed, 27 Jan 2016 14:19:08 GMT

got humidty -6, temperature -46

RE: I2C interface with HTU21D using nrf51822

rushin — Wed, 27 Jan 2016 14:18:32 GMT

here i am also getting wrong humidity

RE: I2C interface with HTU21D using nrf51822

rushin — Wed, 27 Jan 2016 14:05:08 GMT

thanks. i tried it. but its not working for me

RE: I2C interface with HTU21D using nrf51822

Fredrik Sundt Brynhildsvoll — Wed, 27 Jan 2016 12:07:13 GMT

Edit: Added a function that read the temperature.

Is this question resolved? I have actually implemented this sensor (HTU21D) in one of my projects, so I should be able to help.

First of all: I would recommend you to use the function nrf_delay_ms() to delay the microcontroller. To use this you must include "nrf_delay.h"

You are writing to the registers 0xE3 and 0xE5. As stated in the datasheet of HTU21D this is "hold master" mode. When using a hold master mode the argument xfer_pending must be set to 'true': nrf_drv_twi_tx(p_twi_master,slave_addr, &reg_addr,1,true);

I have rewritten your function for reading the humidity. I cannot test it right now, but I believe it should work.

void HTU21D_Humidity1(int *r) {
ret_code_t ret_code;
uint8_t htu21d_address = 0x40; //7 bit address of HTU21D
uint8_t trigger_humidiy_no_hold_master = 0xF5; //Address to humidity reading with no hold of twi lines
uint8_t returned_over_I2C[3] = {0,0,0}; //Array to hold data

ret_code = nrf_drv_twi_tx(p_twi_master, htu21d_address, &trigger_humidiy_no_hold_master, 1, true);//Writing 0xE5 to HTU21D tell the sensor to start humidity readings and hold the master
nrf_delay_ms(50);//Delay 50 ms, which is the maximum measurement time stated in datasheet
ret_code = nrf_drv_twi_rx(p_twi_master, htu21d_address, returned_over_I2C, 3, false); //Get raw humidity data
nrf_delay_ms(5);
//Calculate humidity
uint16_t rawHumidity = ((unsigned int) returned_over_I2C[0] << 8) | (unsigned int) returned_over_I2C[1];
float tempRH = rawHumidity / (float)65536; //2^16 = 65536
float rh = -6 + (125 * tempRH); //From page 14 in datasheet
*r = (int)(rh); // this could be change to (int)(rh*10), then one decimal of the humidity data will be kept (but 34.5  = 345 ) 
}

Function that read the temperature:

void HTU21D_Temperature1(float *r){
ret_code_t ret_code;
uint8_t htu21d_address = 0x40; //7 bit address of HTU21D
uint8_t trigger_temperature_no_hold_master = 0xE3; //Address to temperature reading with no hold of twi lines
uint8_t returned_over_I2C[3] = {0,0,0}; //Array to hold data

ret_code = nrf_drv_twi_tx(&p_twi_instance, htu21d_address, &trigger_temperature_no_hold_master, 1, true);//Writing 0xE3 to HTU21D tell the sensor to start temperature readings and hold the master
nrf_delay_ms(50);//Delay 50 ms, which is the maximum measurement time stated in datasheet
ret_code = nrf_drv_twi_rx(&p_twi_instance, htu21d_address, returned_over_I2C, 3, false); //Get raw temperature data
nrf_delay_ms(5);
uint16_t x = (returned_over_I2C[0]<<8) | returned_over_I2C[1];
float tempRH = x /(float) 65536; //2^16 = 65536
float rh = -46.85 + (175.72 * tempRH);
*r=rh;
}

RE: I2C interface with HTU21D using nrf51822

rushin — Tue, 26 Jan 2016 14:22:10 GMT

yes but these are much and random delay. i will change it and update it

RE: I2C interface with HTU21D using nrf51822

bjorn-spockeli — Tue, 26 Jan 2016 14:06:07 GMT

In HTU21D_Temperature you have a two 200 second delays, delay_ms(200000) and in HTU21D_Humidity you have two 10 second delays, delay_ms(10000). Is that correct?

RE: I2C interface with HTU21D using nrf51822

rushin — Tue, 26 Jan 2016 13:55:38 GMT

but i have not put delay in temperature function as per datasheet. may be this is reason. so first i should check this then i will tell you

RE: I2C interface with HTU21D using nrf51822

rushin — Tue, 26 Jan 2016 13:54:34 GMT

yes i am facing problem

RE: I2C interface with HTU21D using nrf51822

bjorn-spockeli — Tue, 26 Jan 2016 13:51:58 GMT

So you get incorrect values if you call HTU21D_Temperature() and HTU21D_Humidity() back to back?

RE: I2C interface with HTU21D using nrf51822

rushin — Sat, 23 Jan 2016 14:56:31 GMT

anyone have solution??

RE: I2C interface with HTU21D using nrf51822

rushin — Sat, 23 Jan 2016 04:55:53 GMT

it is working for other microcontroller. so i think problem is in code. can anyone suggest me??

RE: I2C interface with HTU21D using nrf51822

rushin — Fri, 22 Jan 2016 13:19:22 GMT

i think i should use interrupt handler. like when one I2C read is completed then second I2C read will start

RE: I2C interface with HTU21D using nrf51822

rushin — Fri, 22 Jan 2016 13:15:17 GMT

how to check clock?? i have not DSO. I think there is problem in code.

RE: I2C interface with HTU21D using nrf51822

Alex — Fri, 22 Jan 2016 13:12:00 GMT

Sorry for misunderstanding. I mean if I were you I would check clock. So you check clock and may be try to match line with resistor or even small cap.

RE: I2C interface with HTU21D using nrf51822

rushin — Fri, 22 Jan 2016 13:04:54 GMT

ok check it and tell me

RE: I2C interface with HTU21D using nrf51822

Alex — Fri, 22 Jan 2016 08:10:58 GMT

I'd check I2C clock line, can be noisy/ringing.

RE: I2C interface with HTU21D using nrf51822

rushin — Thu, 21 Jan 2016 15:28:29 GMT

in BMP180 there is common register for temperature and pressure 0XF6. so i am facing same problem

RE: I2C interface with HTU21D using nrf51822

rushin — Thu, 21 Jan 2016 15:26:34 GMT

I am facing same problem in bmp180