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The
RST
pin can be driven low to reset the Motoron; see
for more details.
The
VM
pin provides access to the reverse-protected motor supply voltage.
You can optionally power the Raspberry Pi by supplying 5 V to the
VREG
pin. To help achieve this,
the Motoron M3H256 has adjacent VM, GND, and VREG pins which you can connect to a
[https://www.pololu.com/category/136/voltage-regulators]
. The regulator should be connected in the
correct orientation so that the Motoron’s VM pin connects to the regulator’s power input and the
regulator’s power output connects to VREG. The motor power supply must be in the allowed input
voltage range of the regulator, and the regulator must output 5 V (or something close enough to be
tolerated by the Raspberry Pi). The regulator must also be able to supply enough current for the
Raspberry Pi (e.g. 3 A for a Raspberry Pi 4). An ideal diode circuit on the Motoron prevents reverse
current from flowing from the Raspberry Pi to the VREG pin if the Raspberry Pi is separately powered
(for example, through its USB power receptacle). However, we do not recommend connecting external
USB power to the Raspberry Pi while it is powered through the Motoron, since recent versions of the
Raspberry Pi (including the 4 Model B and 3 Model B+) do not have a corresponding diode on their
USB power input, so it is possible for the Motoron to backfeed a USB power adapter through the
Raspberry Pi.
Powering the Raspberry Pi’s 5V pin from an
external regulator connected to VM on a Motoron
M3H256.
The
5V
pin connects to the pin of the same name on the Raspberry Pi. It is also the output of the ideal
diode circuit.
Pololu Motoron Motor Controller User’s Guide
© 2001–2022 Pololu Corporation
5. Motoron M3H256 pinout
Page 27 of 67