thank you for your reply. I'v tried to only use the CS pin and it works, but... yes, there is always a but :-) the results are not very accurate. From the moment a set a brightness in the screen, the values of the temperatures grows.

I try to read the temp in a separate task, but it didn't change anything.

Here is my code

#include "Adafruit_MAX31855.h"
#include <SPI.h>
#include <M5Stack.h>

// Example creating a thermocouple instance with software SPI on any three
// digital IO pins.
#define MAXCS   17

Adafruit_MAX31855 thermocouple(MAXCS);

void task1(void * pvParameters) {
  for (;;) {
    float avg = 0;

    /* Read nbReadToAvg times to make an average of the temp */
    for (int i = 0; i < nbReadToAvg; i++) {
      float c = thermocouple.readCelsius();
      avg = avg + c;
      delay(100);
    }

    avg = avg / nbReadToAvg;
    Serial.println(avg);
  }
}


void setup() {

  Serial.begin(115200);
  Serial.print("MOSI=");
  Serial.println(MOSI);
  Serial.print("MISO=");
  Serial.println(MISO);
  Serial.print("SCK=");
  Serial.println(SCK);
  Serial.print("SS=");
  Serial.println(SS);

  thermocouple.begin();
  
  Serial.print("Internal Temp = ");
  Serial.println(thermocouple.readInternal());

  while (!Serial) delay(1); // wait for Serial on Leonardo/Zero, etc

  Serial.println("MAX31855 Initializing ...");

  //  M5.Lcd.setTextColor(WHITE, BLACK);

  // wait for MAX chip to stabilize
  delay(1000);

  xTaskCreatePinnedToCore(
    task1,
    "task1",
    4096,
    NULL,
    1,
    NULL,
    0
  );

  Serial.println("M5 begin without LCD");
  M5.begin(false, false);
  delay(10000);
  Serial.println("LCD Start");
  M5.Lcd.begin();
  for(int j=0;j<100;j++) {
    //Serial.printf("Brigthness=%d\n", j);
    M5.Lcd.setBrightness(j);
    delay(200);
  }
  //delay(10000);
  Serial.println("LCD Shutdown set Brightness to 20");
  M5.Lcd.setBrightness(10);
  //M5.Lcd.sleep();
  M5.Lcd.setTextSize(4);
  M5.Lcd.print("test");
  M5.update();
}

void loop() {

}

And here is the result :

20.27
20.50
20.35
20.45
20.27
18.52
20.12
20.58
20.42
LCD Start
20.27
18.60
21.55
22.73
21.58
21.77
21.98
20.87
21.40
22.40
21.65
23.60
23.40
24.02
24.48
24.62
24.55
29.67
26.83
25.52
29.15
LCD Shutdown set Brightness to 20
23.48
22.27
22.15
21.50
22.92
20.50
21.67
22.60
21.92
22.12
22.42

Why can see that between the line LCD start and the LCD shutdown, the temperature grows and that why the brightness of the screen is increasing. After the line "LCD Shutdown" the brightness is set to 20 and the value are higher that the values at the beginning but they don't moved.

MAX DO -> M5Stack MISO (GPIO19)
MAX CS -> M5Stack GPIO17
MAX CLK -> M5Stack CLK (GPIO18)

Looks like You have connection prepared corectly...

Change only Your sketch like this:

#include <SPI.h>
#include <Adafruit_MAX31855.h>
//#include <M5Stack.h>

// Example creating a thermocouple instance with software SPI on any three digital IO pins.
//#define MAXDO   19
//#define MAXCLK  18
#define MAXCS   17

Adafruit_MAX31855 thermocouple(MAXCS);

void setup() {
  //M5.begin();
  Serial.begin(115200);
  Serial.print("Internal Temp = ");
  Serial.println(thermocouple.readInternal());
  
  while (!Serial) delay(1); // wait for Serial on Leonardo/Zero, etc
  
  Serial.println("MAX31855 test");

  thermocouple.begin();

  // wait for MAX chip to stabilize
  delay(2000);
}

void loop() {

  // basic readout test, just print the current temp
  Serial.print("Internal Temp = ");
  Serial.println(thermocouple.readInternal());
  
  double c = thermocouple.readCelsius();
  if (isnan(c)) {
    Serial.println("Something wrong with thermocouple!");
  } else {
    Serial.print("C = ");
    Serial.println(c);
  }
 
  delay(1000);

  //M5.update();
}

thermocouple.begin();

Thank you for the reply.

Wich pin do you think I have to use for the CS ? No matter wich one ? In the MAX31855 I've 5 pins

• GND
• VCC (3v3)
• DO
• CS
• CLK

If I only initialize the object with the CS, what must I do with the other pins (DO and CLK) ?

Sorry for this question, but I'm a begginer

Adafruit_MAX31855 thermocouple(MAXCS);

as You see at library source: https://github.com/adafruit/Adafruit-MAX31855-library/blob/master/Adafruit_MAX31855.cpp
when You declare SPI CLK line then library try read this device by software SPI implementation!

also You are forgot thermocouple.begin();

Indeed I forgot to include the SPI lib, but unfortunetaly the result isn't good. The values jump between positive and negastives and I do nothing.

Internal Temp = 68.12
Something wrong with thermocouple!
Internal Temp = -111.87
Something wrong with thermocouple!
Internal Temp = 33.75
Something wrong with thermocouple!
Internal Temp = -120.00
C = 1548.50
Internal Temp = 32.63
C = 530.00
Internal Temp = 33.56
Something wrong with thermocouple!

#include <SPI.h>

That file should already be on your system if you followed standard setup for the M5Stack - it should be located in:

C:\Users\YOUR USER NAME\Documents\Arduino\hardware\espressif\esp32\libraries\SPI\src

Perhaps give that a try with the M5Stack commands enabled.

Further tweaks may be required....

#include <Adafruit_MAX31855.h>
//#include <M5Stack.h>

// Example creating a thermocouple instance with software SPI on any three digital IO pins.
#define MAXDO   19
#define MAXCS   17
#define MAXCLK  18

Adafruit_MAX31855 thermocouple(MAXCLK, MAXCS, MAXDO);

void setup() {
  //M5.begin();
  Serial.begin(115200);
  Serial.print("Internal Temp = ");
  Serial.println(thermocouple.readInternal());
  
  while (!Serial) delay(1); // wait for Serial on Leonardo/Zero, etc
  
  Serial.println("MAX31855 test");

  // wait for MAX chip to stabilize
  delay(2000);
}

void loop() {

  // basic readout test, just print the current temp
  Serial.print("Internal Temp = ");
  Serial.println(thermocouple.readInternal());
  
  double c = thermocouple.readCelsius();
  if (isnan(c)) {
    Serial.println("Something wrong with thermocouple!");
  } else {
    Serial.print("C = ");
    Serial.println(c);
  }
 
  delay(1000);

  //M5.update();
}

And the result is

Internal Temp = 32.50
C = 17.25
Internal Temp = 32.56
C = 15.25
Internal Temp = 32.56
C = 18.25
Internal Temp = 32.50
C = 16.50
Internal Temp = 32.56
C = 17.25
Internal Temp = 32.63
C = 18.50
Internal Temp = 32.56
C = 18.25
Internal Temp = 32.63

But if I uncomment the line 3 lines to include M5 to the projet, the result is:

Internal Temp = 0.00
C = 0.00
Internal Temp = 0.00
C = 0.00
Internal Temp = 0.00
C = 0.00
Internal Temp = 0.00
C = 0.00
Internal Temp = 0.00
C = 0.00
Internal Temp = 0.00
C = 0.00

I think is something about the SPI, but I'm not sure. I try to use other pins but unfortunately unsucessfully

When I test my code in a ESP32, it's OK. When I test my code in the M5Stack without the M5.begin(), it's ok, but when I include de M5.begin, the value returned by the MAX6675 are 0

Is there any solution ?

Thanks!

Going to try using a different LCD library.

Should get back to work... looking forward to having a hack tonight :)

I should also point out that the M5Stack device is the master, and the slave is receiving the data ok, the M5Stack device is just not getting the ACK/getting the reply.