I want to send data between different Arduinos distributed in different places: Something like this: https://forum.arduino.cc/t/arduino-master-slave-communication-using-rs485-and-modbus-protocol/644168
I created my own Arduino shield based on this RS485 board:
When I connect two Arduinos using two of these boards, I can send data from one to the other. But when I use at least one of mine, nothing happens.
- power in the RS485 with multimeter.
- pins matching Arduino to Shield.
- Disconnecting the GND between the boards as my circuit has R28 and C22 that are not in the original board.
- Connecting the GND of the Arduinos togheter.
I don't know what else I can do. I saw R25 and R27 can be smaller. Any suggestions? Should I remove R28 and C22? Should I reduce R25 and R27?
This is how my schematic:
When designing the schematic, I crossed by mistake A and B and it is mentioned in @MF3 answer. With this error, R25 and R27 are pulling up and down the lines in the wrong way and it is not working. After removing them, I can connect my shield and one of the boards mentioned without any problem.
The current configuration is: