[solved] ESP-01, i2c, MCP23017 and the arduino IDE

[StefanL38]

If you use wire.begin() without any parameters the wire-library will use those IO-pins that are used as the default for I2C. And these IO-pins are GPIO 4 and 5 which are not accessible on an ESP-01

I did a quoogling with keywords "arduino esp8266 using other io-pins for I2C"

and found this

ESP8266 Change i2c pins

spycatcher2k: GPIO 4 is SDA GPIO 5 is SCL 2 seconds on GOOGLE : ESP8266-12 Pinout was all it took. There is another, perhaps more up to date, point of view on this matter: ESP8266 Thing Hookup Guide - SparkFun Learn It implies that one can indeed change the I2C pins: Wire – The ESP8266 should work with any I2C sensor you can throw at it – just use the same Wire API calls you’re used to. There are a few differences: Pin definition: The ESP2866 doesn’t actually have any hardware I2C pins…

so user @Deva_Rishi found a tutorial how to use a ESP8266-01 module to use I2C.

To me personal this is too much hassle for using an adapterboard for programming the ESP-01. I prefer using ESP32 nodeMCU-boards with which 8 PWM-channels can be created without any additional chips.

Plug in USB-cable upload code and it is ready to run the 8 PWM-channels

best regards Stefan