I’m very new to programming and I’m playing with a aht21 temp and humidity sensor with my duo. I’m working off the C sdk. I’ve been able to recognize the sensor and send the 3 byte trigger measurement command with WriteReg16 . The sensor returns 7 bytes of information and I need to read all of them. WiringX doesn’t seem to have a way to do this. If I try to use 7 individual wiringXI2CRead(), I just get the 1st byte over and over. Like I said I’m new to all of this so I hope this is easy. Thanks
1 Like
I tried to do it with WiringX, but unless I am mistaken it can’t be done with WiringX. I ported some of my old MicroPython i2c bitbang code over to C and got it working. It can definitely be improved, but it works. I start it with a shell script to pinmux the pins I used as GPIO. Don’t forget your pullup resistors on the SDA and SCL lines. Have fun with it. (Oh ya, if you’re trying to copy my breadboard wiring a lot of those wires are leftovers from the Sharp Memory LCD. I didn’t feel like pulling them all out yet.)
aht21b.c
#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <wiringx.h>
#include "aht21b.h"
unsigned char i2c_address = 0x38;
int dat = 10;
int clk = 11;
int dely = 10;
int delyhalf = 5;
unsigned char tri[3];
unsigned long int six[6];
unsigned char temp[1];
int main(){
float temperature_c,temperature_f,humidity;
init();
while(1){
i2c_address = i2c_address & 0xfe; //clear low bit to write
i2c_start();
write3(0xac,0x33,0x00); //trigger measurement
i2c_stop();
usleep(100000); //wait for measurement
//should check status here, but delay is long enough
i2c_address = i2c_address | 0x01; //set low bit to read
i2c_start();
for(int i=0;i<5;i++) //read first 5 bytes of measurement
six[i] = i2c_read();
six[5] = i2c_read_nack(); //read 6th byte with nack to end (skip crc)
i2c_stop();
//convert temperature
float i = ((six[3] & 0x0f) << 16) | (six[4] << 8) | six[5];
temperature_c = ((i / 1048576) * 200) -50;
temperature_f = ((temperature_c * 9) / 5) + 32;
printf("Temperature: %.1fF - %.1fC\n",temperature_f,temperature_c);
//convert humidity
i = ((six[1] << 16) | (six[2] << 8) | six[3]) >> 4;
humidity = (i / 1048576) * 100;
printf("Humidity: %.1f\n\n",humidity);
sleep(2);
}
}
void write3(unsigned char one,unsigned char two,unsigned char three){
tri[0] = one;
tri[1] = two;
tri[2] = three;
for(int i=0;i<3;i++)
i2c_write(tri[i]);
}
int init(void){
if(wiringXSetup("duo", NULL) == -1) {
wiringXGC();
return -1;
}
// shift address over to high bits and slide in write bit at 0
i2c_address = i2c_address << 1;
pinMode(dat,PINMODE_OUTPUT);
pinMode(clk,PINMODE_OUTPUT);
digitalWrite(dat, LOW); //dat == 0 when set as output
digitalWrite(clk, LOW); //clk == 0 when set as output
pinMode(dat,PINMODE_INPUT); //dat pin high
pinMode(clk,PINMODE_INPUT); //clk pin high
usleep(100000); //stabilization delay
}
//*************************
//* bitbang I2C functions *
//*************************
unsigned char i2c_write(unsigned char x){
unsigned char i;
usleep(dely);
for(i=0;i<8;i++){ //clock out data byte
pinMode(dat,PINMODE_OUTPUT); //set data bit low
if(x & 0x80) //if output bit is high
pinMode(dat,PINMODE_INPUT); //then set data bit high
i2c_clock(); //clock it out
x <<= 1; //shift next bit into position
}
//get ack
pinMode(dat,PINMODE_INPUT); //set data high
pinMode(clk,PINMODE_INPUT); //set clock high
usleep(delyhalf); //wait half a clock pulse
if(digitalRead(dat)) //sample the data bit
return(1); //if high then nack error
usleep(delyhalf); //ack good, wait other half of clock pulse
pinMode(clk,PINMODE_OUTPUT); //set clock low
usleep(dely);
pinMode(dat,PINMODE_INPUT); //set data high
return(0);
}
void i2c_start(void){ //send start condition
pinMode(dat,PINMODE_OUTPUT); //set data low
usleep(dely);
pinMode(clk,PINMODE_OUTPUT); //set clock low
usleep(dely);
i2c_write(i2c_address);
}
void i2c_stop(void){ //send stop condition
pinMode(dat,PINMODE_OUTPUT); //set data low
usleep(dely);
pinMode(clk,PINMODE_INPUT); //set clock high
usleep(dely); //stop delay
pinMode(dat,PINMODE_INPUT); //set data high
usleep(dely);
}
void i2c_clock(void){
pinMode(clk,PINMODE_INPUT); //set clock high
usleep(dely);
pinMode(clk,PINMODE_OUTPUT); //set clock low
usleep(dely);
}
void i2c_restart(void){ //send start condition
pinMode(dat,PINMODE_INPUT); //release data
usleep(dely);
pinMode(clk,PINMODE_INPUT);
usleep(dely);
pinMode(dat,PINMODE_OUTPUT);
usleep(dely);
pinMode(clk,PINMODE_OUTPUT);
usleep(dely);
}
unsigned char i2c_read(void){
unsigned char i,tmp = 0;
static unsigned char mbit = 0;
usleep(dely); //10uS delay
for(i=0;i<8;i++){
pinMode(dat,PINMODE_INPUT); //data pin high
usleep(dely); //minimum clock low time
pinMode(clk,PINMODE_INPUT); //clk high
usleep(delyhalf); //1/2 min clock high time
mbit = digitalRead(dat); //read the data bit
if(mbit) //store it in tmp
tmp = tmp | 0x01;
usleep(delyhalf); //last 1/2 min clock high time
if(i < 7)
tmp <<= 1; //shift left for next bit
pinMode(clk,PINMODE_OUTPUT); //clk low
usleep(dely); //minimum clock low time
}
pinMode(dat,PINMODE_OUTPUT);
digitalWrite(dat, 0); //clear data & send ACK
usleep(dely); //data settle time
i2c_clock(); //pulse the clock
pinMode(dat,PINMODE_INPUT); //release ACK
usleep(dely); //gap between next byte
return(tmp);
}
unsigned char i2c_read_nack(void){
unsigned char i,tmp = 0;
static unsigned char mbit;
usleep(dely);
for(i=0;i<8;i++){
pinMode(dat,PINMODE_INPUT); //data high
usleep(dely); //minimum clock low time
pinMode(clk,PINMODE_INPUT); //clk high
usleep(delyhalf); //1/2 min clock high time
mbit = digitalRead(dat); //read the data bit
if(mbit) //store it in tmp
tmp = tmp | 0x01;
usleep(delyhalf); //last 1/2 min clock high time
if(i < 7)
tmp <<= 1; //shift left for next bit
pinMode(clk,PINMODE_OUTPUT); //clk low
usleep(dely); //minimum clock low time
}
pinMode(dat,PINMODE_OUTPUT);
digitalWrite(dat,LOW); //clear data
pinMode(dat,PINMODE_INPUT); //send NACK
usleep(dely); //data settle time
i2c_clock(); //pulse the clock
return(tmp);
}
aht21b.h
void write3(unsigned char,unsigned char,unsigned char);
int init(void);
unsigned char i2c_read(void);
unsigned char i2c_read_nack(void);
unsigned char i2c_write(unsigned char);
void i2c_start(void);
void i2c_restart(void);
void i2c_stop(void);
void i2c_clock(void);
aht21b-script
duo-pinmux -w GP10/GP10
duo-pinmux -w GP11/GP11
./aht21b
1 Like
Thanks. It totally answers my question, it’s too bad you can’t use wiringX to read the aht21. I’ll give you code a try. I should be able to get it running.
2 Likes
See if you think temperature readings seem a little bit high with the AHT21B. If you’ve read my web page about it, I was musing about whether it reads high (probably not), or the conversion isn’t quite right (maybe), or if it’s spot on and my thermostats are both off. But last night I had thermostat set to 70F - house seemed comfortable. And the AHT21B program said it was 72.9F! I don’t think so, but maybe. I might tinker with calibration later.
1 Like
I got a DHT-11 sort of working on the Duo last night. According to its measurements the AHT21B is dead on. My Honeywell T4 Pro thermostat reads almost 3 degrees F too low. Guess I should open it up and see if there’s a calibration trimpot in there somewhere.
Getting DHT-11 working with no access to timers is a bit hard, and so far it’s not reliable. My crappy code gets stuck pretty often. Using C clock is too slow, as the DHT-11 uses timing of 26 to 28uS. Maybe I can fix it today. Maybe not.
1 Like
I guess my other thermometers are reading low as well because I was getting readings that were a little high as well.
1 Like
You got it working with your library?
Does this mean that wiringX library is broken?
1 Like
I got the aht21 working on my rpi pico, I havn’t been able to get to work with the duo and wiring x. You cloud bitbang it with wiringx or write driver that controls the i2c peripheral on the chip directly . As far as that temp sensor, yes wiringx is broken. I haven’t explored using i2c tools and the linux system to control that sensor. It would be nice if we could get the source code for wiringx as I don’t think it would be that much of a change to get it to read 3 bytes in a row. In general I’ve found wiringx to be a disappointment if you want to do anything more than turn a gpio on and off.
1 Like
I have found this: GitHub - wiringX/wiringX: Modular GPIO interface , but it doesn’t support duo…
1 Like
Yeah, I’ve used that a lot to try and figure out how to use some features of wiringx, but we really need the code for the port to the duo.
1 Like
Maybe we don’t even need that wiringx library
Check this doc @ page 20
1 Like
Thats very interesting, I I wondered if wiringx was going thru the kernel space to access the peripherals or addressing the hardware it’s self? I did make a program to run ws2812 and I used the pwm directly and I still had trouble getting the speed I needed. I highly doubt going thru the kernel would have been fast enough. Either way I’ll have to look at it some more.
1 Like
Did you get the WS2812s working? I wanted to try to control 4 of them on my board.
1 Like
yes I did for the 64. it should work on pin GP2/PWM10 if I recall correctly.
2 Likes