Dear all!

I want to communicate to a variable message sign controller through minicom (initially) to see if the controller is really talking to my linux machine.
When I connect my laptop with it and initialize the COM3 modem on that controller, it responds to me by sending an AT command (AT&FS0=1) and that is the only thing that I can see on my minicom. After that I am supposed to send it HDLC frame, as mentioned in the engineering manual of the device, and I send the controller that frame with proper delimiters but it is not responding.

I am totally blank on how to fix this problem. Please help me out you all good brains!

Thanks
Umair

Welcome to LinuxQuestions.
You have not provided enough information to know if you are communicating with the sign correctly.

Can you post the make and model number of the message sign? Or maybe provide a link?
Is minicom configure for the correct port, and serial settings i.e. baud rate, parity etc.?

I can't really provide any information about the controller language itself (because of Non-disclosure agreement) but yeah it is an ADDCO SC4 sign controller mounted on a trailer. I have got two technical documents related to that controller, one is regarding the port settings and parameters etc, and the other is more technical containing some HDLC codes to communicate with the controller in its own language.
Everything is properly confirgured as far as I know. The controller is supposed to communicate with 19200, 8N1 setting which is what I have also set my minicom to. I have to set the port COM3 of the controller using a handheld terminal and when I initialize the port, it sends out the initialization string to my minicom (written in previous post). But after that I have tried to send even some AT commands as well as proper HDLC commands to the controller but it never responds.
The manual has said that it should respond if a proper HDLC frame is sent. To my knowledge my frame is accurate but even if it is not, the controller should respond "NACK".

Getting confused...COM3 is a Windows serial port designation. For Linux/Minicom, it should be something like /dev/ttyS3 or similar. The AT&F indicates you're setting the device back to factory default, and the S0=1 is echo on/DSR high, if I remember correctly. Just try typing in AT&F and see what happens, and try entering other commands and skipping that step, since you've already reset it.

Hey TBOne!
The controller has got 4 serial ports, and according to their name designation, the port used to let the computers or phone communicate with the controller is called COM3. I have connected my computer running Fedora8 Linux to that COM3 port using a USB to serial connector (and have connected RS232 61601 cable to extend the link length). On linux machine that port is termed /dev/ttyUSB0.

Let me check first writing AT&F I hope it might work, thanks!

Ah, that makes sense. I knew Linux didn't have a COM3 device. Also, you mentioned in another thread troubles with TX/RX pins in the cable?? That would be the first thing to address. Without known good, working hardware, lots of time can be wasted.

Hey TBOne!

Thanks! but with this what I now am thinking is that even if I was not connecting the Tx pin with the Rx pin, the controller was responding to me by issuing the "AT&FS0=1" command. So my question now is that is that possible that we connect the pins in wrong way and still get the response from the hardware we are communicating to?

Regards,

You bet....you may be able to transmit/receive, but if the device is expecting to get DSR/DTR high, and your cable is bad, you'll never make headway. Get your hardware straight first, then tackle the software. And, if the instructions reference Windows w/hyperterminal, you should try that first, to make sure all the pieces of your setup are what the instructions expect.

Also...Fedora 8 is VERY old.

Hi!
Today I tested communicating with the controller and put the cable to make a half duplex connection (Tx connected to Rx), but couldn't be successful. That controller is just sending me the AT&FS0=1 command and after that does nothing. I think my hardware is right, it's just that I am not sending the commands through minicom in a right way (maybe) or something else. I am blank!

Any idea on what to try next?
Thanks