If you apply power to the Metro through the power jack, you can disconnect/reconnect from p5.js. There’s a tiny power switch between the USB port and power connector that needs to be flipped to handle external power.
- Connect Arduino to computer, download sketch.
- Disconnect Arduino, collect data
- Connect Arduino to computer, run p5.js connection and read data
Here’s a simple Arduino sketch and p5.js script: memory-example