Wemos D1 and MAX6676 Thermocouple

It took me a while to find out how to connect MAX6676 to Wemos D1 to read temperature. Many references suggested to use Wemos D1 pins D6-D8 but this fails. Following pinout works:

  • D5 – SCK
  • D6 – CS
  • D7 – S0

Here is the sample code with correct pin definitions:

  Average Thermocouple
  Reads a temperature from a thermocouple based
  on the MAX6675 driver and displays it in the default Serial.
  Created by Yurii Salimov, May, 2019.
  Released into the public domain.
#include <MAX6675_Thermocouple.h>
#include <Thermocouple.h>

#define SCK_PIN D5
#define CS_PIN D7
#define SO_PIN D6

Thermocouple* thermocouple;

// the setup function runs once when you press reset or power the board
void setup() {

  thermocouple = new MAX6675_Thermocouple(SCK_PIN, CS_PIN, SO_PIN);

// the loop function runs over and over again forever
void loop() {
  // Reads temperature
  const double celsius = thermocouple->readCelsius();
  const double kelvin = thermocouple->readKelvin();
  const double fahrenheit = thermocouple->readFahrenheit();

  // Output of information
  Serial.print("Temperature: ");
  Serial.print(" C, ");
  Serial.print(" K, ");
  Serial.println(" F");

  delay(500); // optionally, only to delay the output of information in the example.

OTA Update for an ESPhome Device

After installing the ESPhome firmware to my SH-P01s I quickly noticed I had to update the firmware settings. It turned out that updating the firmware is easy after the device is running on ESPhome.

First I had to find out the IP of the device. I used nmap for this. First I connected my laptop to the same network with the relays and then:

$ nmap -sL

Starting Nmap 7.60 ( https://nmap.org ) at 2020-02-24 22:11 EET
Nmap scan report for
Nmap scan report for
Nmap scan report for
Nmap scan report for relay_1.your.localdomain (
Nmap scan report for
Nmap scan report for
Nmap scan report for relay_2.your.localdomain (
Nmap scan report for
Nmap scan report for
Nmap done: 256 IP addresses (0 hosts up) scanned in 0.32 seconds

It was easy to find the relay 1 and its IP from the nmap output. Now I could edit the firmware configuration and re-compile the firmware. I used the dockerised version of ESPhome:

docker run --rm -v "${PWD}":/config -it esphome/esphome relay_1.yaml upload --upload-port

INFO Reading configuration relay_1.yaml…
INFO Connecting to
INFO Uploading relay_1/.pioenvs/relay_1/firmware.bin (428624 bytes)
Uploading: [============================================================] 100% Done…

INFO Waiting for result…
INFO OTA successful
INFO Successfully uploaded program.


Reflashing Deltaco Smartplug SH-P01 to Work With Home Assistant

Note! This document is not valid any more. The SH-P01 devices I purchased on late 2021 were running a patched firmware. Thus, the Tuya-convert is not able to flash the SH-P01s.

This is a documentation of a ongoing work where I’m trying to get Deltaco Smartplug SH-P01 to work with Home Assistant.

Since the Home Assistant does not have a native support for the device I’m planning to:

  • Create an ESPhome firmware with the configuration I found from the Home Assistant discussion board
  • Flash the firmware with tuya-convert
  • Finally, control the device with Home Assistant

Creating ESPhome Firmware

Since I already had Docker installed on my laptop I entered

docker pull esphome/esphome

and got the ESPhome Docker image. After this I created relay_1.yaml with following content:

  name: relay_1
  platform: ESP8266
  board: esp01_1m

# Your WiFi SSID and passphrase is defined here
# https://esphome.io/components/wifi.html
  ssid: "YOUR_WLAN_SSID"

# Enable fallback hotspot (captive portal)
# In case the device can't connect the host defined above
# it starts to work as an access point with these settings
# https://esphome.io/components/captive_portal.html
    ssid: "Smartplug Deltaco 1"


# Enable logging

# Enable Home Assistant API
# https://esphome.io/components/api.html

# Enable Over The Air update component
# https://esphome.io/components/ota.html

  - platform: gpio
      number: GPIO13
      mode: INPUT_PULLUP
      inverted: True
    name: "Deltaco SH-P01 Button"
      - switch.toggle: deltaco_relay_1
  - platform: status
    name: "Deltaco SH-P01 Status"

  - platform: esp8266_pwm
    id: deltaco_smartplug_blue_led
      number: GPIO5
      inverted: True
  - platform: gpio
    name: "Deltaco SH-P01 Relay"
    id: deltaco_relay_1
    pin: GPIO12

  - platform: monochromatic
    name: "Deltaco SH-P01 blue LED"
    output: deltaco_smartplug_blue_led

This was taken from the discussion board referred above. All I needed to do was to edit the SSIDs and passwords and compile a new firmware:

docker run --rm -v "${PWD}":/config -it esphome/esphome relay_1.yaml compile

This printed a lot of debug information and ended with following lines:

Building .pioenvs/relay_1/firmware.bin
Retrieving maximum program size .pioenvs/relay_1/firmware.elf
Checking size .pioenvs/relay_1/firmware.elf
DATA: [===== ] 45.3% (used 37148 bytes from 81920 bytes)
PROGRAM: [==== ] 41.5% (used 425048 bytes from 1023984 bytes)
Creating BIN file ".pioenvs/relay_1/firmware.bin" using ".pioenvs/relay_1/firmware.elf"
========================= [SUCCESS] Took 29.83 seconds =========================
INFO Successfully compiled program.

And yes, the compiled firmware was at .esphome/build/relay_1/.pioenvs/relay_1/firmware.bin! All I needed to do is to get this firmware to the device.

Flashing the Firmware with tuya-convert

The tuya-convert offers a docker image to make the flashing, but I could not make it work. Therefore I installed the script and required packages directly to my Ubuntu as instructed in the README:

git clone https://github.com/ct-Open-Source/tuya-convert
cd tuya-convert
nano -w config.txt
# Changed value WLAN to my device name, wlx7cdd901255af
# Enumerate your device names with "ifconfig"
sudo ./install_prereq.sh

At this point I disconnected by WLAN from the local access point so it was available for tuya-convert. I also copied the ESPhome firmware.bin to tuya-convert/files/relay_1.bin. Then it was time to start the flashing script:

sudo ./start_flash.txt

When instructed I joined my phone to new WLAN access point “vtrust-flash” and after this was done I reset my SH-P01. It took me a while to understand why it did not respond when I pressed the button for the magic 6 seconds. Finally it turned out that the device already had connected to the AP.

The script did the trick. First it downloaded the firmware backup and after that it asked which binary file I wanted to install. After a while the relay_1.bin was uploaded.

Installing Home Assistant

Since I have a Xen server I installed the Home Assistant to a fresh VM running Debian Stretch. The Home Assistant configuration was quite uneventful as everything went as planned.

Since the server and the SH-P01 were on the same network segment (same LAN) the switch was discovered right away. All I needed to do was to give the API password I defined in relay_1.yaml and wrote to the ESPhome firmware.

Everything worked: the relay, the light and the button.

Flashing More Devices

To add more devices just make a copy of the ESPhome configuration (relay_1.yaml) and edit the esphome:name -setting:

  name: relay_2
  platform: ESP8266
  board: esp01_1m

The device names must be unique and they’re used for example as a hostname of the device. Home Assistant creates its ID:s from device names (e.g. “Deltaco SH-P01 Relay” becomes “switch.deltaco_sh_p01_relay”). In case you’re worried about these entity ID:s you might want to give distinctive names to avoid overloading (“switch.deltaco_sh_p01_relay_2”, “switch.deltaco_sh_p01_relay_3” etc.). You might also want to change some of the passwords. After this just repeat the steps with the new firmware.

The sample configuration toggles the relay when the button is pressed. If you don’t want this behaviour but want to control the relays by the Home Assistant automations just remove this codeblock:

  - switch.toggle: deltaco_relay_1