CMU200 remote control over usb to rs232

[aAmecareth]

Hello everyone,

I'm new to working with this kind of device and i have troubles just setting a simple serial link between my computer and the CMU200. I'm using a usb to serial cable in order to perform remote control. I currently use Debian Jessi as it is a constraint of my project and can't use windows to perform my task. My problem is that i tried communicating with the CMU200 using putty and when the connection opens i just got nothing. The putty terminal stays black and the CMU200 seems to receive nothing as the remote control is not triggered. I don't really know where it could come from, i've seen in my search that it coulb be a problem with the quality of the cable i'm using but i was wondering if anyone had a similar problem or if not, a recommended usb to serial cable.

Best regards

[Minions]

A real simple test to determine of your RS-232 serial wiring is working is to short the TX and RX wires together at the end of the cable and see if your commands are echoed back on your terminal as received data.  This does not ensure that your port configurations are correct for communicating with the end device - only that the cabling will work at the current setting.  Next, verify your port settings on the end equipment then configure your USB-Serial port on your terminal for those settings.

[aAmecareth]

Hi,

Thanks for the reply.

The problem is I have no way of doing what you suggest my options are really limited due to what I have at my disposal. I'm not able to rewire the cable to test it that way. I'm gonna try another cable with Tx and Rx led testifiers but I have to wait to get it 😞

[matrixabdul]

auto remote problem in rs232 connection with Keithley 2400 problem. Anybody knows about it, Please tell.

[aAmecareth]

Hi,

So here i am with a new cable with a TX led. This time i can see that data is sent but can't really know if it's received. My main problem is i don't seem to be able to establish a direct link over serial with either putty or minicom. I succeeded in sending files over with minicom but i can't send direct lines as it appears offline in the minicom status. Any idea where it could come from?

[Minions]

The only other things to consider here are if the RS-232 is using any handshaking and that your cable must ensure that TX from your controller is tied to RX on the piece equipment.  If no handshaking is used, you may want to tie off the handshaking - similar to the attachment on the controller side.  Is the ground (DB9-pin 5) wired through to your equipment?

[JÞB]

Those R&S devices can be a pain especially the discontinued models.

First you need to look at the device communication parameters. Are you using COM1 or COM2 on the device? Are you connected physically to that port?  Are you connections correct? (You did read section 8 of the manual right?) have you configured the serial parameters of the device to match your hardware?  Do you know the default settings a 9600, 8, 1, None, SWHS? for a COM port configured for control? (9600, 7 ,2, none SWHS) for COM Ports configured for data transfer. Are you configured for control on the attached port?

What are your COM port settings on the PC? 

What USB to serial converter are you using? Can it drive a logic low that the RS device can read? (Yup- ya need a negative output at least 3 V below GND to get a low.  Guess why that csu200 is discontinued- it uses old tech)

So, nothing mind-bending here you simply need to check your system configuration.

[aAmecareth]

Hello Jeff thank you for your response.

I'm using the COM1 port as it is the one configured for remote control and yes i did check the settings so i have the same ones on my computer, I even tried different ones by changing the baud rate and handshake protocols but nothing changed.

Computer side i'm plugged directly on usb and the converter is recognize as it should:

[   13.595652] usbserial: USB Serial support registered for generic
[   13.620933] usbcore: registered new interface driver pl2303
[   13.620960] usbserial: USB Serial support registered for pl2303
[   13.620996] pl2303 3-2:1.0: pl2303 converter detected
[   13.621721] usb 3-2: pl2303 converter now attached to ttyUSB0

I'll try to see if there is any specific drivers for the cable i use it's a UC232A and keep you posted if i find anything

As i mentioned i'm just a developer and i'm having a hard time dealing with this kind of electronic issues 😛

Thank you again for your support

[JÞB]

Ah, the Prolific chip set!

It won't work without an external level shifter.

FTDI has some options with integrated level shifters to operate at voltages that emulate a RS 232 interface

Essentially that R&S COM interface expects RS-232 to be +/- 12V but is +/- 5V compliant and the converter you have provides 0-3.3V logic.  So, it sees "Maybe" a logic 1 but never a logic 0  I'm betting that the device never even goes into remote.

Now you know what the RS in RS-232 means.  (Recommended Standard)

[aAmecareth]

Thank you so much !!

I could have searched a really long time before figuring it out.