BlueFox/micropython-rp2-rs485-examples
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Added Prerequisites and Wiring sections to README.md

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@ -11,12 +11,39 @@ Here's a short list of the different programs and what they do:
- **rs485_receive.py**: receives utf-8 encoded strings and prints them out as soon as a \n is received.
- **rs485_pingpong.py**: this implements a simple ping-pong over two channels (4 converters needed). For more information, see [Wiring].
- **rs485_pingpong.py**: this implements a simple ping-pong over two channels (4 converters needed). For more information, see [[Wiring]].
## Prerequisites
To be able to run all the examples successfully, you need two MicroPython-enabled Microcontrollers (Raspberry Pi Pico 1 tested) and 4 TTL-UART to RS485 converters, with two of them connected to each μController (see [[Wiring]]).
Also, both microcontrollers should have MicroPython running on them (at time of writing this the latest tested version was 1.23.0).
If you met all these requirements, let's start wiring the parts together!
## Wiring
TODO
For the (simple) send and receive programs, theres just to devices with MicroPython (rp2 flavor tested) needed, as well as two TTL-UART to RS485 converters, one connected to each of them. For the ping-pong example, you will need two channels (one for sending and one for receiving) for each MicroPython device. When using WaveShares Pico 2-Channel HAT, no wiring (between converters and microcontroller) is needed at all!
Just wire two MicroPython devices as shown below (obviously connect different converters to the different microcontrollers ;)
| Converter | Pin on converter | Pin on Pi Pico<sup>1</sup> |
| ----------------------------------------- | -------------------- | --------------------------- |
| TTL-UART to RS485 converter 1 | DI (driver in) | GP0 (UART0 TX) |
| TTL-UART to RS485 converter 1 | RO (receiver out) | GP1 (UART0 RX) |
| TTL-UART to RS485 converter 1 | DE (driver enable) | GP2 (set HIGH/LOW) |
| TTL-UART to RS485 converter 1 | RE (receiver enable) | GP2 (set HIGH/LOW) |
| TTL-UART to RS485 converter 2<sup>2</sup> | DI (driver in) | GP4 (UART1 TX) |
| TTL-UART to RS485 converter 2<sup>2</sup> | RO (receiver out) | GP5 (UART1 RX) |
| TTL-UART to RS485 converter 2<sup>2</sup> | DE (driver enable) | GP3 (set HIGH/LOW) |
| TTL-UART to RS485 converter 2<sup>2</sup> | RE (receiver enable) | GP3 (set HIGH/LOW) |
[<sup>1</sup>] as I used the Pico, adjust for your favourite microcontroller (but don't forget also changing the pinout in the programs as well1)
[<sup>2</sup>] only needed for the ping pong example
Then, connecting the A+, B- and GND wires of the respective converters together (converter 1 of μC1 to converter 1 of μC2, converter 2 of μC1 to converter 2 of μC2), you've just created a simple RS485 bus! Now upload the scripts to both Microcontrollers and try what you want to try!
## Useful links