gu50
commented
1 year ago This can be closed. In the end, it seems to have been caused by a marginal Pico that incidently started working as soon as a small capacitance (i.e. oscilloscope probe or trimmer) was added to the clock pin and always stopped working when removed.
A different Pico solved the issue, so there's nothing special needed for the I2C network between the two hosts I tried.
I've tried a few ways to cable two Picos on a pico VGA baseboard together for an I2c network game. Looking on pins 18 and 19, with an oscilloscope, the host seems to at least be doing something (I can see some activity on both), but as soon as I start the second one as a client the activity dies and the 3.3V sometimes even drops down to zero persistently until I cut power and restart the pico.
I've added pull-ups to 3.3V on both lines via 10k at first, then went down to 4.7k - both didn't change much, only the host's signal quality seemed to be better this way. Grounds were also bound together between the two raspies, in order to see if that helps.
Is there anything I'm missing? Would it maybe be possible to add a quick network cabeling how-to to the repo if I just royally messed up here? ;)