Max6675 Thermocouple project

  • Hi, just started to explore the MySensors possibilities. The first project I'm building is a High temperature MAX6675 Thermocouple which send data to the MQTT broker.

    So I ordered some parts and started building the gateway with an arduino uno and Ethernet shield. Than connected the Max6675 and gave it a go!

    Although the set-up seems to be quit simple I can not get any temperature read from the sensor?
    If I connect it like some of the samples I found I end up with this:

    0;255;3;0;9;MCO:BGN:INIT GW,CP=R-NGA--,VER=2.1.1
    MAX6675 test
    0;255;3;0;9;MCO:REG:NOT NEEDED
    0;255;3;0;9;MCO:BGN:INIT OK,TSP=NA
    0;255;3;0;9;Attempting MQTT connection...
    0;255;3;0;9;MQTT connected
    0;255;3;0;9;Sending message on topic: mygateway1-out/0/255/0/0/17
    0;255;3;0;9;Sending message on topic: mygateway1-out/0/255/3/0/11
    0;255;3;0;9;Sending message on topic: mygateway1-out/0/255/3/0/12
    0;255;3;0;9;Sending message on topic: mygateway1-out/0/10/0/0/6
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan
    Deg C = nan	 Deg F = nan

    I used this example for the wiring: link to max6675-temp-module-wiring

    Also had a look at the post about the max6675 here on the forum. After trying several combinations I run out of ideas. So maybe one of you can point me in the right direction to get this finally working 🙂

    This is the sketch I ended up after changing it several times.

     * The MySensors Arduino library handles the wireless radio link and protocol
     * between your home built sensors/actuators and HA controller of choice.
     * The sensors forms a self healing radio network with optional repeaters. Each
     * repeater and gateway builds a routing tables in EEPROM which keeps track of the
     * network topology allowing messages to be routed to nodes.
     * Created by Henrik Ekblad <>
     * Copyright (C) 2013-2015 Sensnology AB
     * Full contributor list:
     * Documentation:
     * Support Forum:
     * This program is free software; you can redistribute it and/or
     * modify it under the terms of the GNU General Public License
     * version 2 as published by the Free Software Foundation.
     * Version 1.0 - Henrik Ekblad
     * The W5100 MQTT gateway sends radio network (or locally attached sensors) data to your MQTT broker.
     * The node also listens to MY_MQTT_TOPIC_PREFIX and sends out those messages to the radio network
     * LED purposes:
     * - To use the feature, uncomment WITH_LEDS_BLINKING in MyConfig.h
     * - RX (green) - blink fast on radio message recieved. In inclusion mode will blink fast only on presentation recieved
     * - TX (yellow) - blink fast on radio message transmitted. In inclusion mode will blink slowly
     * - ERR (red) - fast blink on error during transmission error or recieve crc error
     * See for wiring instructions.
     * nRF24L01+  ESP8266
     * VCC        VCC
     * CE         GPIO4
     * CSN/CS     GPIO15
     * SCK        GPIO14
     * MISO       GPIO12
     * MOSI       GPIO13
     * Not all ESP8266 modules have all pins available on their external interface.
     * This code has been tested on an ESP-12 module.
     * The ESP8266 requires a certain pin configuration to download code, and another one to run code:
     * - Connect REST (reset) via 10K pullup resistor to VCC, and via switch to GND ('reset switch')
     * - Connect GPIO15 via 10K pulldown resistor to GND
     * - Connect CH_PD via 10K resistor to VCC
     * - Connect GPIO2 via 10K resistor to VCC
     * - Connect GPIO0 via 10K resistor to VCC, and via switch to GND ('bootload switch')
      * Inclusion mode button:
     * - Connect GPIO5 via switch to GND ('inclusion switch')
     * Hardware SHA204 signing is currently not supported!
     * Make sure to fill in your ssid and WiFi password below for ssid & pass.
    // Enable debug prints to serial monitor
    #define MY_DEBUG
    // Enables and select radio type (if attached)
    //#define MY_RADIO_NRF24
    //#define MY_RADIO_RFM69
    // Set this node's subscribe and publish topic prefix
    #define MY_MQTT_PUBLISH_TOPIC_PREFIX "mygateway1-out"
    #define MY_MQTT_SUBSCRIBE_TOPIC_PREFIX "mygateway1-in"
    // Set MQTT client id
    #define MY_MQTT_CLIENT_ID "mysensors-1"
    // W5100 Ethernet module SPI enable (optional if using a shield/module that manages SPI_EN signal)
    //#define MY_W5100_SPI_EN 4
    // Enable Soft SPI for NRF radio (note different radio wiring is required)
    // The W5100 ethernet module seems to have a hard time co-operate with
    // radio on the same spi bus.
    #if !defined(MY_W5100_SPI_EN) && !defined(ARDUINO_ARCH_SAMD)
    #define MY_SOFTSPI
    #define MY_SOFT_SPI_SCK_PIN 14
    #define MY_SOFT_SPI_MISO_PIN 16
    #define MY_SOFT_SPI_MOSI_PIN 15
    // When W5100 is connected we have to move CE/CSN pins for NRF radio
    #ifndef MY_RF24_CE_PIN
    #define MY_RF24_CE_PIN 5
    #ifndef MY_RF24_CS_PIN
    #define MY_RF24_CS_PIN 6
    // Enable these if your MQTT broker requires usenrame/password
    #define MY_MQTT_USER ""
    #define MY_MQTT_PASSWORD ""
    // Enable MY_IP_ADDRESS here if you want a static ip address (no DHCP)
    #define MY_IP_ADDRESS 192,168,0,87
    // If using static ip you need to define Gateway and Subnet address as well
    #define MY_IP_GATEWAY_ADDRESS 192,168,0,1
    #define MY_IP_SUBNET_ADDRESS 255,255,255,0
    // MQTT broker ip address or url. Define one or the other.
    #define MY_CONTROLLER_IP_ADDRESS 192, 168, 0, 36
    // The MQTT broker port to to open
    #define MY_PORT 1883
    // Enable inclusion mode
    // Enable Inclusion mode button on gateway
    // Set inclusion mode duration (in seconds)
    // Digital pin used for inclusion mode button
    // Set blinking period
    // Flash leds on rx/tx/err
    // Uncomment to override default HW configurations
    //#define MY_DEFAULT_ERR_LED_PIN 16  // Error led pin
    //#define MY_DEFAULT_RX_LED_PIN  16  // Receive led pin
    //#define MY_DEFAULT_TX_LED_PIN  16  // the PCB, on board LED
    #include <Ethernet.h>
    #include <MySensors.h>
    // Sample Arduino MAX6675 Arduino Sketch
    #include "max6675.h"
    #define MY_NODE_ID 10
    #define CHILD_ID_TEMP 10
    int thermoSO = 8;
    int thermoCS = 9;
    int thermoSCLK = 10;
    MAX6675 thermo(thermoSCLK, thermoCS, thermoSO);
    int vccPin = 3;
    int gndPin = 2;
    MyMessage msg(CHILD_ID_TEMP, S_TEMP);
    void presentation()  { 
      // Send the sketch version information to the gateway and Controller
      sendSketchInfo("Temp Sensor", "0.1");
      // Register all sensors to gateway (they will be created as child devices)
      present(CHILD_ID_TEMP, S_TEMP);
    void setup() {
    // use Arduino pins 
      pinMode(vccPin, OUTPUT); digitalWrite(vccPin, HIGH);
      pinMode(gndPin, OUTPUT); digitalWrite(gndPin, LOW);
      Serial.println("MAX6675 test");
      // give the MAX a little time to settle
    void loop() {
      // basic readout test
       Serial.print("Deg C = "); 
       Serial.print("\t Deg F = ");



  • Any ideas on this any one? How to troubleshoot this? Would be nice to get this working. Thanks