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// This piece of code allows me to control my dimmer using voice commands. It sends the brightness via I2C to
// an ATTiny-coprocessor, which is connected to a zero-cross-detectore/phase-start-triac module.
// This is mainly a generated example from the fauxmo library for ESP8266, to control the light via Alexa/Amazon-Echo-Dot.
// Example altered to send brightness via I2C (Wire library) to ATTINY Coprocessor, and added OTA update.
// I took the external webserver version instead of the embedded one, to have the option to add some
// html / rest-api calls later on. Not used yet (just a debug message on the root html page).
// Connect ESP D3 to SDA pin 5 of the ATTiny Coprocessor (see+use AvrDimmerCoprocessor_V3).
// Connect ESP D4 to SCK pin 7 of the ATTiny.
// Thijs Kaper, October 2019.
#include <Arduino.h>
#include <ESP8266WiFi.h>
#include <ESPAsyncWebServer.h>
#include "fauxmoESP.h"
#include <ESP8266mDNS.h>
#include <WiFiUdp.h>
#include <ArduinoOTA.h>
#include <Wire.h>
#define SDA_PIN D3 // 0 // GPIO0 - this pin has an external pull-up resistor, which is needed for I2C also.
#define SCL_PIN D4 // 2 // GPIO2 - same comment as above...
const int16_t I2C_MASTER = 0x42;
const int16_t I2C_SLAVE = 0x08;
int brightness = 0; // range 0-100% to I2C
int current_brightness = 1;
// Ugly hardcoded WIFI settings - new WifiManger wouldn't work together with old fauxmo library at first attempt (gave up on it).
#define WIFI_SSID "xxxx"
#define WIFI_PASS "xxxx"
fauxmoESP fauxmo;
AsyncWebServer server(80);
#define SERIAL_BAUDRATE 115200
// -----------------------------------------------------------------------------
// Wifi
// -----------------------------------------------------------------------------
void wifiSetup() {
// Set WIFI module to STA mode
// Connect
Serial.printf("[WIFI] Connecting to %s ", WIFI_SSID);
// Wait
while (WiFi.status() != WL_CONNECTED) {
// Connected!
Serial.printf("[WIFI] STATION Mode, SSID: %s, IP address: %s\n", WiFi.SSID().c_str(), WiFi.localIP().toString().c_str());
String msg = "ok";
void serverSetup() {
// Custom entry point (not required by the library, here just as an example)
server.on("/index.html", HTTP_GET, [](AsyncWebServerRequest *request){
request->send(200, "text/plain", "status: " + msg);
// Custom entry point (not required by the library, here just as an example)
server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
request->send(200, "text/plain", "status: " + msg);
// These two callbacks are required for gen1 and gen3 compatibility
server.onRequestBody([](AsyncWebServerRequest *request, uint8_t *data, size_t len, size_t index, size_t total) {
if (fauxmo.process(request->client(), request->method() == HTTP_GET, request->url(), String((char *)data))) return;
// Handle any other body request here...
server.onNotFound([](AsyncWebServerRequest *request) {
String body = (request->hasParam("body", true)) ? request->getParam("body", true)->value() : String();
if (fauxmo.process(request->client(), request->method() == HTTP_GET, request->url(), body)) return;
// Handle not found request here...
// Start the server
void setup() {
// Init serial port and clean garbage
// Wire.begin(SDA_PIN,SCL_PIN); // initialize I2C (move down to initial setting of brightness)
// Wifi
// Web server
// Set fauxmoESP to not create an internal TCP server and redirect requests to the server on the defined port
// The TCP port must be 80 for gen3 devices (default is 1901)
// This has to be done before the call to enable()
fauxmo.setPort(80); // This is required for gen3 devices
// You have to call enable(true) once you have a WiFi connection
// You can enable or disable the library at any moment
// Disabling it will prevent the devices from being discovered and switched
// You can use different ways to invoke alexa to modify the devices state:
// "Alexa, turn dimmer on" ("dimmer" is the name of the first device below)
// "Alexa, turn on dimmer"
// "Alexa, set dimmer to fifty" (50 means 50% of brightness)
// Add virtual device(s)
fauxmo.onSetState([](unsigned char device_id, const char * device_name, bool state, unsigned char value) {
// Callback when a command from Alexa is received.
// You can use device_id or device_name to choose the element to perform an action onto (relay, LED,...)
// State is a boolean (ON/OFF) and value a number from 0 to 255 (if you say "set dimmer light to 50%" you will receive a 128 here).
// Just remember not to delay too much here, this is a callback, exit as soon as possible.
// If you have to do something more involved here set a flag and process it in your main loop.
// if (0 == device_id) digitalWrite(RELAY1_PIN, state);
// if (1 == device_id) digitalWrite(RELAY2_PIN, state);
// if (2 == device_id) analogWrite(LED1_PIN, value);
Serial.printf("[MAIN] Device #%d (%s) state: %s value: %d\n", device_id, device_name, state ? "ON" : "OFF", value);
// use map function to change 0-255 to 0-100 range.
brightness = map(value, 0, 255, 0, 100);
if (!state) {
// OFF
brightness = 0;
if (brightness < 0) brightness = 0;
if (brightness > 100) brightness = 100;
// text for display on the "root" html page of this device, simple wireless debugging...
msg = "state " + String(state) + ", value " + String(value) + ", brightness " + String(brightness);
// Make this updateable over the air...
// Note: reminder for myself: DO NOT FORGET to enable SPIFFS memory in the arduino gui, e.g. flash 4M, spiffs 2M.
// No OTA possible without SPIFFS.
ArduinoOTA.setPassword((const char *)"xxxx");
Wire.begin(0, 2); // initialize I2C
Wire.write((byte) brightness);
void loop() {
// fauxmoESP uses an async TCP server but a sync UDP server
// Therefore, we have to manually poll for UDP packets
// I did have some OTA issues, and someone suggested to add MDNS.update().
// In the end I do not think it is needed, but does not do any harm also.
// My OTA issue is that when on cable internet, my router does not pass on the MDNS stuff from the Wifi.
// Both mylaptop and ESP must be on Wifi to have OTA working.
// This is a sample code to output free heap every 5 seconds
// This is a cheap way to detect memory leaks
static unsigned long last = millis();
if (millis() - last > 5000) {
last = millis();
Serial.printf("[MAIN] Free heap: %d bytes\n", ESP.getFreeHeap());
if (current_brightness != brightness) {
Wire.write((byte) brightness);
current_brightness = brightness;
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