Interstate 75 power supply question

Hi Pimoroni!

Just received my sparkly Interstate75 board and a very nice 64x64 matrix, reading through the documents and I’m wondering if it is ok to have the board plugged in via USB and powered from an external PSU through the terminals at the same time?
I’m familiar with using Teensy 3.2s and the OctoWS8211 boards, in that case there is a small tab under the teensy for stopping power coming from the USB when injecting power directly to the OctoWS2811 board.
When using and external PSU, should that just supply power directly to the panel and not connect the terminals on the Interstate75 board, or perhaps just the GND connector?

many thanks!

From the product page (my emphasis):

Interstate 2040 is powered and programmable by USB-C. USB-C is capable of providing up to 3A of power which should be enough to power a single 64x64 (or smaller) panel, assuming you’re not planning anything too eye-bleedingly bright. If you need more power than that (so you can chain multiple panels together, perhaps?) you can inject it into the screw terminals instead.

Exactly as to why I’m asking!

I’m powering the Interstate over USB (I’m thinking to send it control data from a RPi zero2) if I inject power into the terminals I’m effectively putting power in from two places, which could be potentially damaging to the RPi or whatever I’m connecting to the interstate board.

In the case I referred to the teensy board that allows you to isolate the power being inject externally from the USB adapter protecting whatever is attached.

It does say “instead” so I assumed it was an alternative, but it is ambiguous enough to warrant an official answer.

I suppose you could use a data-only USB cable, so you’re only injecting power from the terminals?

Our engineers say:
“[Having USB-C and an external power supply both connected to Interstate] will be fine most of the time, but it depends on the two power supplies. I’d recommend having the led matrix powered direct with an external power supply, and leave the 5V disconnected between the interstate and the led matrix. Connecting the led matrix and Interstate grounds together can help with signal integrity, but isn’t strictly necessary as there’s a couple ground pins connecting the two in the signal header connector.”