Arduino Uno R3 with DFRobot IO Expansion Shield

Projects Networking, Protocols, and Devices
1

Hi there...

I'm trying to send and receive data through RS485. That's why I'm choosing Arduino Uno R3 with DFRobot IO Expansion Shield.
I'm using this code in Arduino Uno R3 to send a byte.

byte[] data = {0x01};
...
Serial.write(data, 1);
delay(1000);
... and over and over again... every 1 second -> send 0x01

So... I think I send 0x01. Then I connect it to my RS485 in my PC and try to read my serial port buffer (using C# SerialPort Class).

And what I get : 0x7F....?

Arduino send 0x01 -> PC receive 0x7F
Arduino send 0x02 -> PC receive 0x3F
Arduino send 0x11 -> PC receive 0x77

Am I missing something here ???

And for the other direction (PC -> Arduino), PC send 0x01 and Arduino receive nothing.
Serial.available() is always 0.

PS : During sketch upload, I remove the IO Expansion Shield. After upload finished, I put it again and set all 3 jumpers to RS485.

Can somebody help me ?

2

Then I connect it to my RS485 in my PC

Your PC has a RS485 jack?

Your post is missing links to the hardware you are using.

3

I have a USB-RS485 Converter in my PC. I check it again, and it's ok, because I have another Industrial ADC and it use also Modbus RTU RS485. It works correctly. Only with Arduino is something wrong.

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