Connecting Alpha Five to RPi via UART pins + RPi power

doublemazaa

Hi! I'd like to control my A5 via a node js script running on an RPi via the UART pins on the Pi.

Should this be able to work?

I'm controlling the A5 through my mac and a USB/Serial cable at the moment, but would love to use less hardware when I get this set up permanently.

I have my pi sending serial to my compute over the same cable, but when I connected to the clock nothing came through. I'm happy to troubleshoot more, but want to confirm this should be possible before banging my head on the table for a night.

 

The other thing is I would love to power my Pi using the A5's power supply. I see the external power pads next to the serial pins. If I step the 9V down to 5V, should there be any issue running my Pi off of this power source?

Thanks.

Windell Oskay

In terms of communication and logic protocols, I don't see any reason why this shouldn't work. However, there is a concern with the logic voltage levels. The Alpha Clock Five uses 5 V logic, and the RPi uses 3.3 V logic. Signals coming from the RPi to the A5 should work fine (the A5 can understand 3.3 V logic inputs), but signals from the A5 to the RPi will be at 5 V, and could damage the RPi input pin if it that pin is connected. It is possible to add a logic level converter (in a few different ways) if you need to get data back. Or perhaps, since it's primarily a display device, you won't mind not getting data back.

If you have the blue or white model of the A5, it comes with a 9 V power supply, and a (small) voltage regulator to step that down to 5 V to drive the on-board logic. (The red model comes with a 5 V power supply.)  The 9 V power supply does have excess capacity, so you can use an additional voltage regulator to drop that down to 5 V to power the RPi. I would not recommend using the on-board regulator to power the RPi; it does not have much excess capacity.