What do you want the 4 motors to do.
Do they need to communicate to each other.
You could possibly use an analog signal on the ‘master’ Crumble to tell the other Crumble to know what to set motors to.
The analog range is 0 – 255
Maybe a binary range
<10 – all off
>10 & < 40 – Motor 1 forward / Motor 2 stop
>40 & < 70 Motor 1 backwards / Motor 2 stop
>70 & <100 Motor 1 stop / Motor 2 forward
>100 & <130 Motor 1 stop / Motor 2 backwards
>130 & <160 Motor 1 forward / Motor 2 forward
>160 & <190 Motor 1 forward / Motor 2 backwards
>190 & <220 Motor 1 backwards / Motor 2 forwards
> 220 Motor 1 backwards / Motor 2 backwards
In this way (hopefully) if you set the signal to a mid-range value like 25, 55, 85, 115,… there should hopefully be enough tolerance so the signal when received will still be in range.
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