MTC-H5 PPP using only 3 wires on linux

[Eric Robishaw]

I’ve got a linux device with only 3 wires: Send, Receive and Ground

I’ve been using The older Multitech MTCBA GPRS modems for years, but am moving to the MTC-H5 (B01) series and cannot get my ppp connection to work anymore.

It fails at the ATD*99***1#, which returns NO CARRIER
BUT, the CD light comes on for a few seconds before this occurs.

I then hooked up to a windows box, and issuing the same ATD*99***1# returns CONNECT immediately.

I then used a 3 wire cable on the windows box, same command, and “NO CARRIER”…

On the modem I’ve turned off flow control using:
AT+IFC=0,0

AND command flow Control Off:
AT#CFLO=0

But I think the modem is doing something with the CTS/RTS lines upon connection and on my linux device without these lines it fails.

Any suggestions?

[Lonny Knudson]

Hi Eric,
Try using AT&K0 to disable flow control. If this doesn’t work, I believe early firmware on the -H5 series modems needed RTS forced on even when flow control was disabled. Try forcing RTS active and see if this resolves the problem. If so, you can either use a custom cable that forces RTS active or update the firmware on your modem. If you would like to update, open a support ticket at http://support.multitech.com and we can get you the firmware and Windows update utility.

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