SHT31 temp/humidity sensor

[ahmedriazku]

Hi, I have a SHT31 temp/humidity sensor and want to connect it thru IIC to Lora TTGO ESP32, Somehow the ESP32 fails to read temp and humidity once the OLED is initialised. I am attaching the code which works with SDA/SCL at 21/22 pins and the OLED initialisation commented. Initializing OLED seems to put off the sensor. I guess its about the IIC already used by the OLED. Any leads or examples where SHT31 Lora ESP32 are used or any hint?

type or paste code here #include <Arduino.h>
#include <Wire.h>
#include "Adafruit_SHT31.h"
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

Adafruit_SHT31 sht31 = Adafruit_SHT31();

//OLED pins
#define OLED_SDA 4
#define OLED_SCL 15 
#define OLED_RST 16
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RST);

void setup()
{
Serial.begin(9600);
if (! sht31.begin(0x44))
{
Serial.println("Couldn't find SHT31");
while (1) delay(1);
}

//reset OLED display via software
//  pinMode(OLED_RST, OUTPUT);
//  digitalWrite(OLED_RST, LOW);
//  delay(20);
//  digitalWrite(OLED_RST, HIGH);
  
  //initialize OLED
//  Wire.begin(OLED_SDA, OLED_SCL);
//  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3c, false, false)) { // Address 0x3C for 128x32
//    Serial.println(F("SSD1306 allocation failed"));
//    for(;;); // Don't proceed, loop forever
//  }
}

void loop()
{
float t = sht31.readTemperature();
float h = sht31.readHumidity();

if (! isnan(t))
{
Serial.print("Temp *C = "); Serial.println(t);
}
else
{
Serial.println("Failed to read temperature");
}

if (! isnan(h))
{
Serial.print("Hum. % = "); Serial.println(h);
}
else
{
Serial.println("Failed to read humidity");
}
Serial.println();
delay(1000);
}

[PaulRB]

@ahmedriazku

I guess its about the IIC already used by the OLED

No, the entire point of i2c bus is that many devices share the same 2 Arduino pins. The devices must each have a different address on the bus, which in your circuit I'm pretty sure they will.

Please clarify, which pins is the sht31 connected to?

Try moving Wire.begin() before sht31.begin().

[ahmedriazku]

The SHT31 is connected : 21/SDA 22/SCL.

[ahmedriazku]

when I move the wire.begin() before sht31.begin() then i get this error: "Couldn't find SHT31"

[ruilviana]

Hi
The SHT31 has 2 I2C addresses.
You select which address to use by its ADDR pin.
I2C address A 0x44 (default) ADDR (pin 2) connected to VSS
I2C address B 0x45 ADDR (pin 2) connected to VDD.

I suggest you run I2CScanner.ino in your project and see what address it will find.

[PaulRB]

@ahmedriazku

when I move the wire.begin() before sht31.begin() then i get this error: "Couldn't find SHT31"

Moving that line should not have caused that error. Please post your updated code.

[ahmedriazku]

type or paste code heretype or paste code here #include <Arduino.h>
#include <Wire.h>
#include "Adafruit_SHT31.h"
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

Adafruit_SHT31 sht31 = Adafruit_SHT31();

//OLED pins
#define OLED_SDA 4
#define OLED_SCL 15 
#define OLED_RST 16
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RST);

void setup()
{
Serial.begin(9600);

  //initialize OLED
  Wire.begin(OLED_SDA, OLED_SCL);
if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3c, false, false)) { // Address 0x3C for 128x32
 Serial.println(F("SSD1306 allocation failed"));
  for(;;); // Don't proceed, loop forever
}

if (! sht31.begin(0x44))
{
Serial.println("Couldn't find SHT31");
while (1) delay(1);
}

//reset OLED display via software
//  pinMode(OLED_RST, OUTPUT);
//  digitalWrite(OLED_RST, LOW);
//  delay(20);
//  digitalWrite(OLED_RST, HIGH);
  

}

void loop()
{
float t = sht31.readTemperature();
float h = sht31.readHumidity();

if (! isnan(t))
{
Serial.print("Temp *C = "); Serial.println(t);
}
else
{
Serial.println("Failed to read temperature");
}

if (! isnan(h))
{
Serial.print("Hum. % = "); Serial.println(h);
}
else
{
Serial.println("Failed to read humidity");
}
Serial.println();
delay(1000);
}

[PaulRB]

Ah, I see. The error is coming from the esp, it is not a compile error.

Try i2c scanner sketch as suggested by @ruilviana

Have you tried any of the example sketches that were installed with the Adafruit_SSD1306 library? If they do not work, disconnect the sht31 and try again.

[ahmedriazku]

The above code with i2C address 0x44 works with the wire.begin() commented. Why would that conflict with Wire.begin()?

[jerryadam]

This might be due to I2C conflict, you can check the detailed tutorial on displaying the data on its own OLED display here: Interfacing SHT31 with ESP32 TTGO LoRa32 and display on its OLED display

[ahmedriazku]

Thanks. I will try and get back to you soon.

[ahmedriazku]

I tried but it shows a hazy screen on oled and on the serial it shows blank. when i rst the ttgo it gives "Couldn't find SHT31". The same ttgo and i run a short Adafruit program that does not involve oled and with gpio 21 and 22 and i get temperature and humidity on the serial.

[danzielin]

Which SHT31 is a direct connect for the Davis Instruments Advantage Pro 2 transmitter. Mine was manufactured in 2020. The humidity and temp sensor went haywire. I purchased an SHT31 board on Amazon. (Not the Davis one) Does not work. It is connected correctly. My older one was the SHT10 of which I just purchased the IC and replaced it. It worked for a few years till transmitter went haywire also.