RS485 to USB question

Hello,

i have two RS485 to USB adapters connected with two wires (A+ to A+, B- to B-).

http://www.amazon.com/KEDSUM®-Converter-Adapter-ch340T-Support/dp/B009SIDMNM

I installed drivers and connected both of them to USB port of computer. In device manager one is shown as COM3 and another one as COM4. I opened "putty" twice and connected to both adapters over serial (one to COM3, another to COM4) with default settings (9600, 8 data bits, 1 stop bit, none polarity, none flow control).

When I try to send something from one to another, nothing happen. Did I made something wrong or what could be wrong?

Br,

Luxy

Try changing the flow control on one of them. They might both be tri-stated. You are using it in half duplex mode.

If you can borrow someone's laptop, try communicating between two computers with the adaptors. This would help by verifying that they are in fact functional and your problem is a configuration problem or something else. If you can't get another laptop, maybe you could try it between a computer and a printer (don't know if that would work because of the driver issue)

aarg:
Try changing the flow control on one of them. They might both be tri-stated. You are using it in half duplex mode.

raschemmel:
If you can borrow someone's laptop, try communicating between two computers with the adaptors. This would help by verifying that they are in fact functional and your problem is a configuration problem or something else. If you can't get another laptop, maybe you could try it between a computer and a printer (don't know if that would work because of the driver issue)

Which settings and how should I change than? I tried to change flow control with all possible combinations but it doesn't help.

Baud: 9600
Data bits: 8
Stop bits: 1
Parity: None, Odd, Even, Mark, Space
Flow control: None, XON/XOFF, RTS/CTS, DSR/DTR

I think I tried something similar and found the problem to be that it was not really a two way connection but rather a 3-way with my computer being the third party. Try a two way connection (only two devices). I was able to get two separate arduinos to output serial on different comm ports and view the output from both on the same desktop but that may be because both USB devices were operating as SLAVEs to the HOST PC. I don't know if your adaptors are SLAVES or HOSTS but I suspect therein lies the problem. Why ? Well if those adaptors are USB HOSTs, then you would have 3 HOSTS all connected together. "Three's a crowd".

raschemmel:
I think I tried something similar and found the problem to be that it was not really a two way connection but rather a 3-way with my computer being the third party. Try a two way connection (only two devices). I was able to get two separate arduinos to output serial on different comm ports and view the output from both on the same desktop but that may be because both USB devices were operating as SLAVEs to the HOST PC. I don't know if your adaptors are SLAVES or HOSTS but I suspect therein lies the problem. Why ? Well if those adaptors are USB HOSTs, then you would have 3 HOSTS all connected together. "Three's a crowd".

I just tried between two computers and it works! :slight_smile:

I used default settings:

Baud: 9600
Data bits: 8
Stop bits: 1
Parity: None
Flow control: None

Now next step is to go from wired to wireles with this:

Well, there you go. Actually, the arduino UNO is a USB SLAVE but 2 HOSTS and 1 SLAVE still doesn't work. It is possible to buy a USB HOST shield but I think you have solved your problem anyway.