About This Project
The SonOff is a small device containing an ESP8266, relay, power supply LED and button on a footprint of 8.5x4 cm. AC/DC goes straight in (and out) the device so precaution should be well in place;
- The device gets hotter (than i.e. a Wemos D1 R2)
- the AC/DC lines do not have an 100% strain relief.
But for $5 a piece you have a complete device to play with. There is already a lot to be found in forums about the SonOff. So far I missed an useful sketch which connected the SonOff to Cayenne MQTT.
- With Over the Air.
- Without credentials for Wifi and Cayenne MQTT inside sketch but inside EEPPROM
And more important I was able to read and understand a bit of it, at least enough to tweak it to my liking.
The sketch is Heavily inspired by: https://github.com/idreamsi/SonoffBoilerplate and GitHub - tzapu/WiFiManager: ESP8266 WiFi Connection manager with web captive portal . I only convert it and made it suitable for myself and the Cayenne MQTT environment.
This is my second attempt to convert the SonOffBoilerplate. In my first attempt I realised I remove too much functionality:smiley:
What’s Connected
Nothing more than the Device and two AC/DC lines
PRECAUTION
My MQTT credentials have in total a length of 112 positions, I use this information to decide if the device needs to go into AP mode to update this, If 112 is not a standard lenght this part of the sketch should be updated
// standard lenght of Cayenne MQTT settings (?) are 36 + 40 + 36 = 112 so if the total size not equal to 112 reset (go into AP-mode)
int sizeme = strlen(settings.MQTT_username) + strlen(settings.MQTT_Password) + strlen(settings.MQTT_ClientID);
Serial.print("lenght setting MQTT strings : ");
Serial.println(sizeme);
if ( sizeme != 112) {
reset();
}
BTW Each field stored in EEPROM is one position longer so this explains the following lines:
#include <EEPROM.h>
#define EEPROM_SALT 12663
typedef struct {
int salt = EEPROM_SALT;
char MQTT_username[37] ; // MQTT username
char MQTT_Password[41] ; // MQTT password
char MQTT_ClientID[37] ; // MQTT Client ID
}
With this principle in mind it becomes easy to add parameter/fields to your sketch, update these in AP modes and store in EEPROM
Preparation:
- follow instructions: GitHub - mirko/SonOTA: Flashing Itead Sonoff devices with custom firmware via original OTA mechanism
- create hex from verified sketch and upload though: GitHub - arendst/Tasmota: Alternative firmware for ESP8266 and ESP32 based devices with easy configuration using webUI, OTA updates, automation using timers or rules, expandability and entirely local control over MQTT, HTTP, Serial or KNX. Full documentation at
- continue inside Arduino IDE
Remarks:
- no need to connect first to eWelink
- DO NOT INSTALL LATEST FIRMWARE eWelink (did once result divice could not use SonOTA)
- Make sketch non distructive comment out things like reset(), restart() if you loop into this you are screwed!
- preferred testing sketch on easy access ESP8266 device like Wemos D1 R2
- a reboot/restart normally goes into error and freeze so this is removed from the Cayenne dashboard as button, with the physical button the SonOff automatically goes into a reboot it you continuously hold the button, if you would do this inside the sketch it will create errors do to a programming error inside the ESP8266
Objectives:
- Solderless programming
- Over the Air updating sketch
- No Wifi and Cayenne MQTT credentials in sketch
- On the fly change of Wi-Fi and MQTT credentials and store in EEPROM (this sometimes requires a second time)
- Synchronisation of SonOff Relay, button and Cayenne Actuator (regardless initiator)
Additional Functionality
- time (from NTP-server)
- Dailight Saving Time / Summertime
- Scheduling based on sunset and sunrise
- Display Wifi signal
- uptime in days, hours minutes (bit stupid)
- version displayed (bit more stupid)
A Puzzle to solve
It puzzled me for a long time how to access Cayenne MQTT, First my sketch stopped at point:
- Cayenne.begin(settings.MQTT_username, settings.MQTT_Password, settings.MQTT_ClientID, SSID, wifiPassword)
At one point a solution was to disconnect WiFI, which worked but still required hard coded SSID and wifiPassword. Next I tried to pick up the SSID and password from WifiManager which is possible but I stranded to convert the array into a string. With my next T&A I just did a very simple thing. Realising I am already on Wi-Fi I just shortened the Cayenne.begin to:
Cayenne.begin(settings.MQTT_username, settings.MQTT_Password, settings.MQTT_ClientID)
Life can be simple sometimes 
Holding physical button SonOff
What happens if you hold the physical button?
- shorter than 1.5 seconds → toggle relay and sync
- between 1.5 - 5.0 seconds → going into AP-modus
- longer → restart SonOff
This is a small change to the original sketch.
Additional SONOFF details:
- Upload as Generic ESP8266 - Flash mode: DOUT - size: 1MB (64 SPIFFS)
- Sonoff header (if you are not working solderless anymore)
1 - vcc 3v3
2 - rx
3 - tx
4 - gnd
5 - gpio 14
The Sketch
SonOff_BoilerPlate_Cayenne.txt (17.9 KB)
Due to problems with upload previous file:
SonOff_BoilerPlate_Cayenne.ino.txt (18.0 KB)
