Riva:
Glad you have one problem sorted and found the next hurdle to jump.
Just to put the old RS485 modules problem to bed how was you connecting them up?
For the old modules I connected them the same way described here.
Essentially:
| Arduino | RS 485 |
|---|---|
| TX | DI |
| RX | RO |
| 3 (Direction Control) | DE / RE |
| GND | GND |
| 5V | VCC |
I don't know whether I got a bad batch or what but I must've re-wired the circuit about 50 times to make sure it was together correctly.
So gawd knows.