MCP23017 library won't compile in Arduino IDE

TECHNICAL SUPPORT Sensors & Modules
1

Customer:

I’m unable to compile blink.ino with the MCP23017 library.

Attachment omitted in migration: Error message Soldered blink 071125.txt

Originally submitted via email support on 7 November 2025. Migrated to the forum for community visibility.

2

Soldered Support:

We were able to compile this on Dasduino CONNECTPLUS, ESP32 dev module and Inkplate board definitions. You need to install the library in your /libraries folder in documents/Arduino, not just in your project folder. This library also uses easyC.hpp internally.

The Arduino compiler requires specific directory structure. Install the library in /libraries and then try File > Examples > Soldered MCP23017 Arduino Library > Blink.