Will https://www.sparkfun.com/products/9947 work with the Red-V? I’m guessing a 5V input is needed, but will it work otherwise?
If I understand correctly only the VIN, GND and SPI connections are needed on the shield to get USB HOST functionality out of it right?
It’s never been tested on the Red-V, I don’t know for sure if it would work or not.
At a minimum, you’d need to write libraries for the Host Shield that work with the Red-V.
There’s 4 wires needed for SPI plus three other signals, any GPIO pin should work for the three other signals though.
TS-Chris:
It’s never been tested on the Red-V, I don’t know for sure if it would work or not.At a minimum, you’d need to write libraries for the Host Shield that work with the Red-V.
There’s 4 wires needed for SPI plus three other signals, any GPIO pin should work for the three other signals though.
Thanks, I use Rust so the need to write the driver is there regardless. If the power/wiring setup is fully compatible tho then this answers my question.
I’m not 100% sure the data lines used for SPI on the shield (11, 12, 13) will do SPI on the Red-V but you can always re-wire them to other pins if they are not.
Another issue you may run into is that the USB Host Shield was designed to work with a 5 volt system like the Arduino Uno, the Red-V is a 3.3 volt system so you’re also likely going to need to level shift between 3.3 and 5 volts between the shield and the Red-V. It probably could be made to work, but it’s not going to be a “plug the shield onto the board and go” type thing. 
TS-Chris:
I’m not 100% sure the data lines used for SPI on the shield (11, 12, 13) will do SPI on the Red-V but you can always re-wire them to other pins if they are not.Another issue you may run into is that the USB Host Shield was designed to work with a 5 volt system like the Arduino Uno, the Red-V is a 3.3 volt system so you’re also likely going to need to level shift between 3.3 and 5 volts between the shield and the Red-V. It probably could be made to work, but it’s not going to be a “plug the shield onto the board and go” type thing.
Oh I thought it powers down? There’s a 5V vin pin on the Red-V and in the shield description it says:
The Host Shield takes its power from the ‘Vin’ pin on your Arduino. Power from that pin is regulated to both 5V and 3.3V on the shield. All SPI signals are sent through a hex converter to step them down to 3.3V.
I thought that means that the signals will be 3.3V
What that’s saying is that the shield takes care of translating the 5 volt I/O you’d find on an Uno or other 5 volt board down to 3.3 volts for the ICs found on the shield. Unfortunately the flip side of that is that the shield also takes the 3.3 volt signals from the ICs and converts those back to the 5 volts it thinks the Arduino is expecting.
Internally the shield runs at 3.3 volts but externally it communicates at 5 volts. Since the Red-V is a 3.3 volt board and the shield is sending 5 volts back to the Red-V, that’s where you’re going to have troubles.
Ah I see. That is unfortunate. I’m guessing there’s no easy hack-ish way to maybe circumvent a small circuit on the shield to keep things at 3.3V?
Possible but not easy to do.
We don’t carry it, but maybe something like this would work for you?
Yes that’s an easier solution. Thanks for being frank!
No problem!