Questions about the Wireless Shell V1 V3 I2C Vext

#1

Hello,
Since I still have three black wireless flashes here, I wanted to use them now.
But how can I use I2C if Vext is also installed on them?
That means both can’t be used, right?
And are the V1 and V3 pins compatible?
Since I can’t get the V1 anymore and would have to use the V3 afterward.
Thanks

#2

I’ve not worked with the Wireless Shell but I believe it’s just the core of the Wireless Stick Lite board, which I have used, and in this case all you have to do, if you want to use Vext, is use something other than GPIO21 (the Vext-Ctrl pin) for the SDA line of the I2C bus.

This is no longer an issue with the V3 boards but the V3 boards are entirely different from anything that preceded them—different ESP32 processor, and therefore different pins, and different LoRa chip.

#3

Thanks.
I’m aware that the pins are slightly different.

It’s also because the V3 documentation doesn’t specify which are the Lora pins.
The V1/2 documentation does. That’s how you know which ones you shouldn’t use.

The normal pins can be assigned by definition.

#4

I’m still looking for a solution.
But if I interpret the schematics correctly, the Lora pins on the V3 aren’t routed to the outside at all.
That would mean that only the pins in the positions where the V1/2 has them can’t be connected, and all the others can be assigned accordingly by definition.

It would be great if someone from Heltec could comment on this.
Thanks

#5

Nope and there’s no need for that to happen and it’s on the SPI bus so not really part of your solution.

If you look at the schematic and identify two lines that do not have any other components on them and are routed to the header, you can tell your I2C setup code to use those pins. It is that simple.

This is because, with a few minor limitations, the ESP32 allows you to route any peripheral to any any IO. The reason there are some defaults is that’s how they are configured upon reset and some are optimised for certain allocations, but for something like I2C at 100kHz, pretty much any routing is fine.