I have connected A to TRX- and B to TRX+
I use a twisted pair cable, length about 1 meter.
I have added a 120 Ohm resistor to both ends.
I open the serial port on Medusa with the same parameters as on PC:
When I send a 8 byte message from PC to Medusa, I get an 4 to 16 byte long response. even that there is currently no code that is reading or sending bytes on Medusa!
The response data contains mostly 0x3f 0x7f and 0xff, but it’s not the same data all the time and it’s not related to what I send.
I also noticed that the RXD LED on my RS232/485 converter on PC side is always on, when Medusa is connected. When I disconnect RS485 module from Medusa (RS485 module is still powered) then the LED goes off.
The USB serial module is disconnected all the time, and the Medusa is rebooted before test.
I also used a different RS485 module with same results.
I assume that medusa is ok, because programming with USB Serial module works without any problems.
Any help here is appreciated.