Hi there –
I’m using the Romi 32U4 control board and I’ve got a much more powerful SBC mounted instead of a Raspberry Pi. This SBC can’t actually run off the 500mA of a standard USB port - it needs at least 1A.
From reading section 3.5 of the control board user guide, I thought this would be OK - that I’d be able to draw up to 2A (when running on battery power).
I’ve got my SBC wired up as if it were a Raspberry Pi, with its power coming via RPI5V. I assumed RPI5V and 5V (i.e. the output of the TPS2113A power multiplexer circuit) were the same thing? But RPI5V seems to max out at 500mA rather than at 2A.
I’ve connected up an Adafruit INA219 high side DC current sensor breakout in order to monitor the current during the SBC’s boot up - all goes well with current consumption rising steadily during the process until it hits just over 500mA for a fraction of a second, at which point the SBC shuts down
Should I connect my SBC to VREG? I guess there’s no point connecting it to the 5V output (that can switch between VREG and 5V USB) as my board can’t use the basic 500mA of USB. You may ask why I don’t simply try this but everything is fully assembled now and I’ll have to take it all apart and solder a connection to VREG first - I’d like to know in advance if this is pointless, i.e. if VREG will provide no more current that RPI5V?
And one more question - the user guide says 2A should be available from VREG. Am I right in thinking this is all that’s available to everything powered off the control board, i.e. the 32U4 MCU, the encoders and in particular the motors and the SBC?
The stall current for the 120:1 mini plastic gearmotor, that the Romi chassis kit uses, is listed as 1.25A. Does this mean if the Romi bumps into a wall, i.e. comes to a sudden complete stop with both motors going at full power, that the two motors together will try to consume 2.5A, i.e. more than the 2A total VREG can supply? Will the SBC then lose power every time the Romi bumps into something? Sorry if I’ve misunderstood the meaning of stall current.