WIZnet Developer Forum

Wiz750SR-RS485 no response in serial command mode

I cannot get a response in serail command ATMode.

Using a Terminal Program: Sending the command mode switch code [2B[2B][2B]

The SE2 Config tool shows Status = ATMode

Sending the MC[CR][LF] or any other command where I expect to see a response, I don’t see any

Finally , Sending the EX[CR][LF], The SE2 Config tool shows Status = UDP

So I believe the WIZ750SR is recognizing the RS485 commands. Also , I can see the correct ASCII text on both the terminal window and the transmitted UDP packets, using WireShark, in data mode

I tried entering the ATMode via the HW_TRIGGER as well as using other terminal programs, WZ750SR and USB/RS485 converter boards with no luck

Any help greatly appreciated


The problem was the wizNet750SR board was in RS422mode, since I had the RS485+/RS485- connected to the 422_RXD+/485+ and 422.RXD-/485- pins , so that makes sense

The problem now is how do I configure for RS485 mode? I tried connecting the 485_SEL pin to both ground and +3.3V with no luck

Any help will greatly appreciated

Hello again,

Looking at the schematic, It looks like the 485_SEL pin should be left open, which is the configuration I have. Connecting it to ground shorts out the 485_DIR signal which forces U6 to be in receive mode. This is what the Eval board does. The 485_DIR should be an CPU output (PA12), that converts U6 from receiver to a transmitter as is done in half-duplex RS485.

So I’m not sure what to do, I’m thinking this may be a firmware bug where the 485_DIR is not being set correctly. The wizNet750SR is loaded with V1.2.4, looks like you’re up to V1.3.3

I really need some help with this as it is impacting my customer deliveries. I would appreciate a response

Hello, I could use some help here, does RS485 com work at all?

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