How to configure pull-up resistors for i2c?

I remember having some trouble with the internal pullups for I2C, and not being able to get it to work (but that could have been on the F1-based original Espruino, not the Pico).

If you wanted to try it, you'd have to use poke to change the value in the pin's registers though, as I believe I2c needs to be in af_opendrain mode, but pinMode won't do that while also providing a pullup.

poke itself isn't desperately dangerous - you can crash Espruino so it needs a reboot, but it would be quite hard to cause physical damage.

... but in short, I'd say external pullups are easier - especially if it's just a solder jumper!