Best practice powering Raspberry Pi 4 + Arduino Nano in embedded system

[elpidiovaldez5]

I am building a small self balancing robot that contains a Raspberry Pi 4 and an Arduino Nano. The Nano handles the motor control and Gyro/Accelerometer communication and the Pi 4 handles wifi, vision and speech. The Pi 4 communicates with the Nano via USB (so no issues with logic voltage level differences between 3.3V Pi and 5V Nano). The system is powered from 4S Lipos using a 5V Buck Converter for the electronics and direct battery power to Motor H-Bridge.

So my question is how to best supply power to the Nano and Pi 4 ?

1. 5V direct to Nano, 5V to GPIO connectors on Pi 4
2. 5V direct to Nano, 5V to GPIO connectors on Pi 4, cut the 5V line on the USB between Pi 4 and Nano.
3. 5V to Pi 4 GPIO, power Nano via USB from Pi 4
4. 5V to Pi 4 using hacked USB-C cable, power Nano via USB from Pi 4
5. Something I've missed.

I have seen a lot of discussion relating to a powered Pi 4 and possible backdriving via USB connections. The accepted technique is to cut the 5v line of the USB connection, however my case is slightly different, since both devices are powered from the same PSU. Any voltage differences would only be due to voltage drop in the wires and possibly providing multiple connections for power would make the power more robust. I am unclear whether the connection via USB is a good or bad thing.

As far as hacking a USB-C cable is concerned, I think this is probably the safest way to supply power to the Pi 4 because there are fuses and protection, but the USB-C cable is much more complicated than previous USB cables and I do not know how to connect power through it. Apparently nor did the Raspberry Pi foundation at first - I have one of the earlier Pi 4 boards which had problems due to a resistor value.

 

[gophert]

The best way is to power the RPi through the USB because using the +5 and ground pins on the pi have some issues (see the official pi site and search external 5v power. I have built several projects with pins and using those header pins to apply power but, there is apparently some risks - I haven't had any problems.
Also, make sure you have at least 1.5 amps to power the pi before voltage sag and more if you have RPi display (2.5A for display + pi).

if you can split a USB cable, that would be best butindividual stranded wires get pretty tiny to deal with.