Background: I'm trying to replace the electronics for a ice hockey scoreboard. The old electronics had the following issues:
- It stop working. I have since discovered that a couple of diodes and capacitors had burnt out.
- The controller was wired. We want to get rid of the wire running down the length of the rink.
- The connectors for the controller gave lots of issues. I have had to re-soldered them countless times.
The scoreboard is approximately 3.5 meters across.
I plan to stick a Raspberry Pi at the scoreboard. I plan to put a wifi usb dongle that support ap mode, and run hostapd. Scorekeepers can then connect to the Raspberry Pi via a web interface from a tablet/laptop.
I plan to replace the incandescent bulbs with LEDs, possibly OSRAM LR G5AP-BZCZ.
I originally planed to use i2c GPIO extenders. But I have since learnt that the wiring for a i2c bus need to be as short as possible. This would mean that I would need a lot of cabling from the gpios to the leds. Hence I arrive at my question.
Question: I would like to have AVR microprocessor for each 7 segment or each 2 7 segments who's job is a GPIO extender. These would be placed physically near to the LEDs. I would like to communicate from Raspberry Pi to the multiple AVR microprocessors over a common serial bus.
I have read that RS-485 can have multiple host on a bus. And as my communication is in one direction (output from the Raspberry Pi,) I hope that this can make the solution simpler.
Can the Raspberry Pi and AVR do RS-485 using there existing serial interfaces? What circuitry is needed to do this?