Need help with thermistor temp reading on: ESP32C3 xiao

ticsy · February 6, 2024, 11:41am

hi. I have made an thermistor temp reading that shos temp on a oled, it works great on arduino uno, only 5 wires in total, but then i bought an ESP32C3, and now it dosent work, i have been reading and asking people for days now, no one is good enough in esp to help
only thing i get on the display is: -273 blinking like hell...

here is my code:
#include <Wire.h> #include <Adafruit_GFX.h> #include <Adafruit_SSD1306.h>


#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, -1);
int ThermistorPin = 0;

int Vo;

float R1 = 10000;

float logR2, R2, T, Tc;

float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;
void setup(){

display.begin(SSD1306_SWITCHCAPVCC,0x3C); //OLED address

display.clearDisplay();

Serial.begin(9600);

}
void loop(){

Vo = analogRead(ThermistorPin);

R2 = R1 * (1023.0 / (float)Vo - 1.0);

logR2 = log(R2);

T = (1.0 / (c1 + c2logR2 + c3logR2logR2logR2));

Tc = T - 273.15;
display.clearDisplay();

display.setTextSize(2);

display.setTextColor(WHITE);

display.setCursor(70, 0);

display.println("C");

display.display();

display.setTextSize(2);

display.setTextColor(WHITE);

display.setCursor(3, 0);

display.println(Tc);

display.display();

delay(10);

}

sterretje · February 6, 2024, 11:59am

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DaveX · February 6, 2024, 12:57pm

The esps have a 12 bit ADC so dividing by 1023 is wrong.

jim-p · February 6, 2024, 12:58pm

Change
Vo = analogRead(ThermistorPin);
To
uint32_t Vo = analogReadMillivolts(ThermistorPin);

Change
R2 = R1 * (1023.0 / (float)Vo - 1.0);
To
R2 = R1 * (((3.3*1000.0)/ float(Vo))-1.0);

ticsy · February 7, 2024, 7:27am

thanks for reply, it worked on arduino uno? so shouldn't it work on esp?
When i change the sentence: uint32_t Vo = analogReadMillivolts(ThermistorPin);
I get error: Compilation error: 'analogReadMillivolts' was not declared in this scope; did you mean 'analogReadMilliVolts'?

jim-p · February 7, 2024, 7:33am

Which board do you select when you compile and upload the sketch?

ticsy · February 7, 2024, 7:37am

xiao_esp32c3

jim-p · February 7, 2024, 7:49am

Try this sketch

void setup() {
  // initialize serial communication at 115200 bits per second:
  Serial.begin(115200);
  
  //set the resolution to 12 bits (0-4096)
  analogReadResolution(12);
}

void loop() {
  // read the analog 
  int analogValue = analogRead(A0);
  int analogVolts = analogReadMilliVolts(A0);
  
  // print out the values you read:
  Serial.printf("ADC analog value = %d\n",analogValue);
  Serial.printf("ADC millivolts value = %d\n",analogVolts);
  
  delay(500);  // delay in between reads for clear read from serial
}

jim-p · February 7, 2024, 7:53am

Use A0 for the pin number

ticsy · February 7, 2024, 7:53am

like this:

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <driver/adc.h>

#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, -1);

int ThermistorPin = 2;
int Vo;
float R1 = 10000;
float logR2, R2, T, Tc;
float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;


void setup() {
  // initialize serial communication at 115200 bits per second:
  Serial.begin(115200);
  
  //set the resolution to 12 bits (0-4096)
  analogReadResolution(12);
}

void loop() {
  // read the analog 
  int analogValue = analogRead(0);
  int analogVolts = analogReadMilliVolts(0);
  
  // print out the values you read:
  Serial.printf("ADC analog value = %d\n",analogValue);
  Serial.printf("ADC millivolts value = %d\n",analogVolts);
  
  delay(500);  // delay in between reads for clear read from serial
}

Now the display is only solid showing: "nan c"

jim-p · February 7, 2024, 7:56am

I trying to find out why it does not like analogReadMillivolts.
Use the sketch exactly as I show in post #9
Check the readings on the serial monitor

ticsy · February 7, 2024, 7:58am

yes it's strange :S, now i lost the screen..

it's like such an easy thing to do in arduino, made it in like 10-15 min, but switch over to the xiao_esp32c3 and everything is messed up xD

jim-p · February 7, 2024, 8:02am

There is no screen in the sketch.
So it did compile with analogReadMillis(A0)
What does the serial monitor show?

ticsy · February 7, 2024, 8:05am

ADC analog value = 3565

ADC millivolts value = 2456

ADC analog value = 3550

ADC millivolts value = 2456

ADC analog value = 3551

ADC millivolts value = 2457

jim-p · February 7, 2024, 8:10am

So the analogReadMillivolts is working.
You must have made a typo when you first tried it.
So your original sketch with the modifications I suggested should compile and work
Try it again

ticsy · February 7, 2024, 8:12am

this is what i have now:

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <driver/adc.h>

#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, -1);

int ThermistorPin = A0;
int Vo;
float R1 = 10000;
float logR2, R2, T, Tc;
float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;


void setup(){
  display.begin(SSD1306_SWITCHCAPVCC,0x3C); //OLED address 
  display.clearDisplay();
  Serial.begin(115200);
  
  //set the resolution to 12 bits (0-4096)
  analogReadResolution(12);
}

void loop(){
  int analogValue = analogRead(A0);
  int analogVolts = analogReadMilliVolts(A0);
  
  // print out the values you read:
  Serial.printf("ADC analog value = %d\n",analogValue);
  Serial.printf("ADC millivolts value = %d\n",analogVolts);
  
  delay(500);  // delay in between reads for clear read from serial
  R2 = R1 * (((3.3*1000.0)/ float(Vo))-1.0);
  logR2 = log(R2);
  T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2));
  Tc = T - 273.15;

  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(70, 0);
  display.println("C");
  display.display();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(3, 0);
  display.println(Tc);
  display.display();
  delay(10);
}

Now it's just showing "-273,15" on display :S

ticsy · February 7, 2024, 8:13am

I copied and pasted the line: uint32_t Vo = analogReadMillivolts(ThermistorPin);

so I couldnt made an typo

ticsy · February 7, 2024, 8:17am

the word volts was with a smal "v" xD but now i could upload this code:

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <driver/adc.h>

#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, -1);

int ThermistorPin = A0;
int Vo;
float R1 = 10000;
float logR2, R2, T, Tc;
float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;


void setup(){
  display.begin(SSD1306_SWITCHCAPVCC,0x3C); //OLED address 
  display.clearDisplay();
  Serial.begin(115200);
  uint32_t Vo = analogReadMilliVolts(ThermistorPin);
  //set the resolution to 12 bits (0-4096)
  analogReadResolution(12);
}

void loop(){
  int analogValue = analogRead(A0);
  int analogVolts = analogReadMilliVolts(A0);
  
  // print out the values you read:
  Serial.printf("ADC analog value = %d\n",analogValue);
  Serial.printf("ADC millivolts value = %d\n",analogVolts);
  
  delay(500);  // delay in between reads for clear read from serial
  R2 = R1 * (((3.3*1000.0)/ float(Vo))-1.0);
  logR2 = log(R2);
  T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2));
  Tc = T - 273.15;

  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(70, 0);
  display.println("C");
  display.display();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(3, 0);
  display.println(Tc);
  display.display();
  delay(10);
}

But still: just blinking -273

jim-p · February 7, 2024, 8:17am

Try this code

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#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, -1);

int ThermistorPin = A0;
int Vo;
float R1 = 10000.0;
float logR2, R2, T, Tc;
float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;

void setup() {
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C); //OLED address
  display.clearDisplay();
  Serial.begin(9600);
}

void loop() {
  Vo = analogReadMilliVolts(2);
  R2 = R1 * (((3.3*1000.0)/ float(Vo))-1.0);
  logR2 = log(R2);
  T = (1.0 / (c1 + c2logR2 + c3logR2logR2logR2));
  Tc = T - 273.15;

  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(70, 0);
  display.println("C");
  display.display();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(3, 0);
  display.println(Tc);
  display.display();
  delay(10);

ticsy · February 7, 2024, 8:19am

now i got: Compilation error: 'c2logR2' was not declared in this scope; did you mean 'logR2'?

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Need help with thermistor temp reading on: ESP32C3 xiao

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