How to enable Home-Assistant MQTT auto-discovery on Tasmota

First, upgrade your Tasmota to the latest firmware. For me, only firmware 10.1.0+ worked with Home-Assistant MQTT autodiscovery.

Then, configure your MQTT server and username/password using the webinterface.

After that, open the console in the webinterface and enter

SetOption19 1

and press return. Now reboot Tasmota using the webinterface.

Posted by Uli Köhler in Home-Assistant

How to fix Tasmota Upload Failed: Upload buffer miscompare on Nous A1T


When trying to do a Tasmota firmware upgrade on the Nous A1T, you see this error message:

Upload Failed
Upload buffer miscompare


This issue occurs because in the default configuration there is not enough flash space to flash the firmware.
However, this is easy to fix: First, flash the tasmota-minimal.bin.gz firmware, then flash the regular tasmota.bin.gz firmware using the webinterface of the minimal firmware.

Download link for the minimal firmware
Download link for the regular firmware

After that, upgrades will work just fine.

Posted by Uli Köhler in Home-Assistant, MQTT

LIRC Setup for Raspberry Pi (Receiver)

Quite simple. Just install it using

sudo apt-get install lirc

Update /boot/config.txt with dtoverlay=gpio-ir,gpio_pin=18

To use lirc in “default” mode (the default mode after installation is “devinput” mode) modify by sudo nano /etc/lirc/lirc_options.conf.

Change to driver = default

BTW: My first post on this blog 🙂

Posted by Tobias Gutmann in Raspberry Pi

How to fix Homeassistant “403: forbidden” on login

When Homeassistant shows you 403: forbidden instead of the login prompt, the most likely cause is that your user got banned due to too many failed login attempts.

Edit configuration.yaml and set

login_attempts_threshold: 100

from the default 5, which should unban you. You might also need to configure the trusted_proxies to contain the IP of a reverse proxy server (typically running on If that does not help, disable the IP ban entirely. This is a complete configuration.yml http section that works:

  use_x_forwarded_for: true
  ip_ban_enabled: false
  login_attempts_threshold: 500


Posted by Uli Köhler in Home-Assistant

How long does portMAX_DELAY actually wait in FreeRTOS?

Although portMAX_DELAY is listed as value for waiting indefinitely, it will only actually wait indefinitely if INCLUDE_vTaskSuspend is enabled in the FreeRTOS config.

portMAX_DELAY is typically defined as 0xFFFFFFFF i.e. 2^32-1:

#define portMAX_DELAY ( TickType_t ) 0xffffffffUL

(however if 16 bit ticks are enabled using configUSE_16_BIT_TICKS it will be defined as 0xFFFF (2^16-1).

In case INCLUDE_vTaskSuspend is enabled, this is treated as a special value and will actually wait indefinitely. If INCLUDE_vTaskSuspend is not defined, it will only wait for 0xFFFFFFFF ticks (assuming 32-bit system ticks.

In other words, this will wait for only about 7 weeks if FreeRTOS is defined to tick every millisecond.

Posted by Uli Köhler in Embedded, FreeRTOS

How to fix PlatformIO ArduinoJSON .pio/libdeps/ESP32/ArduinoJson/src/ArduinoJson/Variant/ConverterImpl.hpp:43:5: error: static assertion failed: To use 64-bit integers with ArduinoJson, you must set ARDUINOJSON_USE_LONG_LONG to 1


While trying to compile your PlatformIO project, you see an error message like

.pio/libdeps/ESP32/ArduinoJson/src/ArduinoJson/Variant/ConverterImpl.hpp:43:5: error: static assertion failed: To use 64-bit integers with ArduinoJson, you must set ARDUINOJSON_USE_LONG_LONG to 1. See https://arduinojson.org/v6/api/config/use_long_long/
In file included from .pio/libdeps/ESP32/ArduinoJson/src/ArduinoJson.hpp:30,
                 from .pio/libdeps/ESP32/ArduinoJson/src/ArduinoJson.h:9,
                 from include/MQTT/StatusMessage.hpp:2,
                 from src/MQTT/StatusMessage.cpp:1:
.pio/libdeps/ESP32/ArduinoJson/src/ArduinoJson/Variant/ConverterImpl.hpp: In instantiation of 'static void ArduinoJson6185_1::Converter<T, Enable>::toJson(const T&, ArduinoJson6185_1::VariantRef) [with T = long long int (*)(); Enable = void]':
.pio/libdeps/ESP32/ArduinoJson/src/ArduinoJson/Variant/VariantRef.hpp:98:27:   required from 'bool ArduinoJson6185_1::VariantRef::set(T*) const [with T = long long int()]'
.pio/libdeps/ESP32/ArduinoJson/src/ArduinoJson/Object/MemberProxy.hpp:58:5:   required from 'ArduinoJson6185_1::MemberProxy<TParent, TStringRef>::this_type& ArduinoJson6185_1::MemberProxy<TParent, TStringRef>::operator=(TChar*) [with TChar = long long int(); TObject = ArduinoJson6185_1::JsonDocument&; TStringRef = const char*; ArduinoJson6185_1::MemberProxy<TParent, TStringRef>::this_type = ArduinoJson6185_1::MemberProxy<ArduinoJson6185_1::JsonDocument&, const char*>]'


Add -DARDUINOJSON_USE_LONG_LONG=1 to the build_flags in platformio.ini. If build_flags does not exist in platformio.ini, create it after [env:...]



Posted by Uli Köhler in Arduino, Electronics, ESP8266/ESP32, PlatformIO

How to install KiCAD 6.0 on Ubuntu

Run this to install KiCAD 6.0:

sudo add-apt-repository ppa:kicad/kicad-6.0-releases
sudo apt update -y
sudo apt -y install kicad


Posted by Uli Köhler in KiCAD, Linux

ESP32 Wireguard example with HTTP access over Wireguard (PlatformIO)

In this example we will use Wireguard-ESP32-Arduino in order to make HTTP requests over Wireguard on the ESP32.

platform = espressif32
board = esp32-gateway
framework = arduino
monitor_speed = 115200
lib_deps =
    ciniml/[email protected]^0.1.5
#include <WiFi.h>
#include <WireGuard-ESP32.h>

// WiFi configuration --- UPDATE this configuration for your WiFi AP
char ssid[] = "MyWifiESSID";
char password[] = "my-wifi-password";

// WireGuard configuration --- UPDATE this configuration from JSON
char private_key[] = "gH2YqDa+St6x5eFhomVQDwtV1F0YMQd3HtOElPkZgVY=";
IPAddress local_ip(10, 217, 59, 2);
char public_key[] = "X6NJW+IznvItD3B5TseUasRPjPzF0PkM5+GaLIjdBG4=";
char endpoint_address[] = ""; // IP of Wireguard endpoint to connect to.
int endpoint_port = 19628;

static WireGuard wg;

void setup()
    Serial.println("Connecting to the AP...");
    WiFi.begin(ssid, password);
    while( !WiFi.isConnected() ) {
    Serial.println("Adjusting system time...");
    configTime(9 * 60 * 60, 0, "ntp.jst.mfeed.ad.jp", "ntp.nict.jp", "time.google.com");

    Serial.println("Connected. Initializing WireGuard...");

void loop()
    WiFiClient client;

     * Connect to
     * python3 -m http.server
    if( !client.connect("", 8000) ) {
        Serial.println("Failed to connect...");
    } else { // Client connected successfully. Send dummy HTTP request.
        client.write("GET /wireguard-test HTTP/1.1\r\n");
        client.write("Host: wireguard.test.com\r\n");


Remember to replace by the IP address of the computer your ESP32 should connect to (i.e. the computer running WireGuard). You also need to enter the correct Wifi credentials.

On the computer, deploy this WireGuard config:

# Name = Computer
PrivateKey = ONj6Iefel47uMKtWRCSMLan2UC5eW3Fj9Gsy9bqcyEc=
Address =
ListenPort = 19628

# Name = ESP32
PublicKey = H3KaL/X94984cLDNWFsM4Hx6Rs/Ku0bW2ECkDUn7wFw=
AllowedIPs =
PersistentKeepalive = 60

which is auto-generated by the following GuardMyWire config:

    "rules": {
        "Node": {
            "connect_to": ["*"],
            "keepalive": 60
    "peers": [
            "name": "Computer",
            "endpoint": "",
            "addresses": [
            "type": "Node",
            "interface_name": "wg0"
        }, {
            "name": "ESP32",
            "addresses": [
            "type": "Node",
            "interface_name": "wg0"

Enable this config and start a Python HTTP server to receive the requests using

python3 -m http.server

Now flash the firmware on the ESP32.

Using wg show you should see the ESP connecting:

interface: Computer
  public key: X6NJW+IznvItD3B5TseUasRPjPzF0PkM5+GaLIjdBG4=
  private key: (hidden)
  listening port: 19628

peer: H3KaL/X94984cLDNWFsM4Hx6Rs/Ku0bW2ECkDUn7wFw=
  allowed ips:
  latest handshake: 5 seconds ago
  transfer: 11.71 MiB received, 10.43 MiB sent
  persistent keepalive: every 1 minute

Look for the

latest handshake: 5 seconds ago


On the shell running python3 -m http.server you should see the dummy HTTP requests: - - [31/Dec/2021 02:36:48] "GET /wireguard-test HTTP/1.1" 404 - - - [31/Dec/2021 02:36:48] code 404, message File not found - - [31/Dec/2021 02:36:48] "GET /wireguard-test HTTP/1.1" 404 - - - [31/Dec/2021 02:36:48] code 404, message File not found - - [31/Dec/2021 02:36:48] "GET /wireguard-test HTTP/1.1" 404 - - - [31/Dec/2021 02:36:48] code 404, message File not found
Posted by Uli Köhler in ESP8266/ESP32, PlatformIO, Wireguard

How to fix HomeAssistant [homeassistant.components.mqtt] Unable to connect to the MQTT broker: Connection Refused: not authorised.


When starting up HomeAssistant, e.g. using docker-compose up, you see this error message:

homeassistant    | 2021-12-27 19:55:46 WARNING (Recorder) [homeassistant.components.recorder.util] The system could not validate that the sqlite3 database at //config/home-assistant_v2.db was shutdown cleanly                                                                                  
homeassistant    | 2021-12-27 19:55:47 ERROR (Thread-3) [homeassistant.components.mqtt] Unable to connect to the MQTT broker: Connection Refused: not authorised.                                                                                                                                 
homeassistant    | 2021-12-27 19:55:47 WARNING (Thread-3) [homeassistant.components.mqtt] Disconnected from MQTT server (5)
homeassistant    | 2021-12-27 19:55:48 ERROR (Thread-3) [homeassistant.components.mqtt] Unable to connect to the MQTT broker: Connection Refused: not authorised.                                                                                                                                 


Your configuration.yml does not have the correct username and/or password for your MQTT server.

This is an example section that works if the MQTT server has the correct user:

  broker: ""
  username: "homeassistant"
  password: "ep2ooy8di3avohn1Ahm6eegheiResh"

Also check if the MQTT server such as Mosquitto has the correct user with the correct password.

Posted by Uli Köhler in Home-Assistant

Simple HomeAssistant docker-compose setup

First, create a directory where HomeAssistant will reside. I use /opt/homeassistant.

Create docker-compose.yml:

version: '3.5'
    container_name: homeassistant
    restart: unless-stopped
    image: ghcr.io/home-assistant/home-assistant:stable
    network_mode: host
    privileged: true
      - TZ=Europe/Berlin
      - ./homeassistant_config:/config
      - mosquitto
    image: eclipse-mosquitto
    network_mode: host
      - ./mosquitto_conf:/mosquitto/config
      - ./mosquitto_data:/mosquitto/data
      - ./mosquitto_log:/mosquitto/log

Now start homeassistant so it creates the default config files:

docker-compose up

Once you see

homeassistant    | [services.d] done.

Press Ctrl+C to abort.

Now we’ll create the Mosquitto MQTT server config file in mosquitto_conf/mosquitto.conf:

persistence true
persistence_location /mosquitto/data/
log_dest file /mosquitto/log/mosquitto.log

listener 1883
## Authentication ##
allow_anonymous false
password_file /mosquitto/config/mosquitto.passwd

Now create the mosquitto password file and fix the permissions using

touch mosquitto_conf/mosquitto.passwd
chown -R 1883:1883 mosquitto_conf

We can now start create the homeassistant mosquitto user using

docker-compose run mosquitto mosquitto_passwd -c /mosquitto/config/mosquitto.passwd homeassistant

Enter a random password that will be used for the homeassistant user

Now we can edit the homeassistant config homeassistant_config/configuration.yml. This is my config – ensure to insert the random MQTT password we used before instead of ep2ooy8di3avohn1Ahm6eegheiResh:

# Configure a default setup of Home Assistant (frontend, api, etc)

  use_x_forwarded_for: true
  ip_ban_enabled: true
  login_attempts_threshold: 5

  broker: ""
  username: "homeassistant"
  password: "ep2ooy8di3avohn1Ahm6eegheiResh"

# Text to speech
  - platform: google_translate

group: !include groups.yaml
automation: !include automations.yaml
script: !include scripts.yaml
scene: !include scenes.yaml

Now we can start the server using

docker-compose up

You can also use our script to generate a systemd service to autostart the docker-compose config on boot:

curl -fsSL https://techoverflow.net/scripts/create-docker-compose-service.sh | sudo bash /dev/stdin

Now login to the web interface on port 8123 and configure your HomeAssistant!

Posted by Uli Köhler in Container, Docker, Home-Assistant, MQTT

FreeRTOS task queue minimal example

This is how you create and use a task queue in FreeRTOS:

Global declaration

Declare the structure of a task (I recommend to use a task type enum class in order to keep the flexibility of using multiple task types:

#include <freertos/queue.h>

enum class I2CTaskType : uint8_t {
    MyTaskType = 0

struct I2CTask {
    I2CTaskType type;
    // Parameters
    int16_t value;
static QueueHandle_t i2cTaskQueue;

Initialization code

Call this once, before using it:

// Create task queue
i2cTaskQueue = xQueueCreate(8 /* Number of queue slots */, sizeof(I2CTask));

In the thread processing the queue

if (xQueueReceive(i2cTaskQueue, (void *)&task, portMAX_DELAY /* Wait infinitely for new tasks */) == pdTRUE) {
    if(task.type == I2CTaskType::MyTaskType) {
        // TODO process task
        Serial.printf("My task type: %d\r\n", task.value);

How to add a task to the queue

void AddTask(int16_t val) {
    I2CTask task;
    task.type = I2CTaskType::MyTaskType;
    task.value = val;
    xQueueSend(i2cTaskQueue, (void*)&task, 10 / portTICK_PERIOD_MS /* timeout */);


Posted by Uli Köhler in C/C++, Embedded, FreeRTOS, PlatformIO

ESPAsyncWebserver handler example with String query argument

This example is based on our basic example and shows how to use an String query parameter, e.g.

server.on("/api/test", HTTP_GET, [](AsyncWebServerRequest *request) {
      String param = request->getParam("param")->value();
      // TODO: Do something with param!

      // Respond with JSON {"status": "ok"}
      AsyncResponseStream *response = request->beginResponseStream("application/json");
      DynamicJsonDocument json(1024);
      json["status"] = "ok";
      json["param"] = param;
      serializeJson(json, *response);


Posted by Uli Köhler in ESP8266/ESP32, Networking

How to insert “null” value in ArduinoJSON

Just use nullptr:

json["myvalue"] = nullptr;

If nullptr is not available, use the equivalent (char*)0:

json["myvalue"] = (char*)0;


Posted by Uli Köhler in Arduino, Embedded

How to fix error: invalid conversion from ‘int’ to ‘esp_mqtt_event_id_t’ on the ESP8266 or ESP32

If you see an error message like

src/main.cpp: In function 'void InitMQTT()':
/home/uli/.platformio/packages/framework-arduinoespressif32/tools/sdk/esp32/include/esp_event/include/esp_event_base.h:37:32: error: invalid conversion from 'int' to 'esp_mqtt_event_id_t' [-fpermissive]
 #define ESP_EVENT_ANY_ID       -1               /**< register handler for any event id */

src/main.cpp:80:44: note: in expansion of macro 'ESP_EVENT_ANY_ID'
     esp_mqtt_client_register_event(client, ESP_EVENT_ANY_ID, mqtt_event_handler, client);

replace ESP_EVENT_ANY_ID by MQTT_EVENT_ANY and recompile. This will fix the issue. Using ESP_EVENT_ANY_ID was possible in an outdated version of the MQTT library.


Posted by Uli Köhler in Arduino, Embedded, ESP8266/ESP32, MQTT, Networking, PlatformIO