brian kusler.
brian kuslerHello.
We’ve been using Multitech MTCBA-G-F2 and F4 modems for years in an application where a custom C application we wrote, running on a PC, talks to the modem over a USB-to-Serial interface. We recently tried using an H5 and our code can’t connect. Neither can the new MultiConnect 100 modem. Oddly, a normal desktop Terminal app has no problems at all with any of the modems. We’ve been trying everything we can think of and it seems like maybe something changed on the flow control between the F4 and the H5…? We’ve confirmed that our code is getting the text TO the modem, but we just can’t get the response back. Any ideas what might have changed about serial behavior between the two version of the modem?
Lonny KnudsonHi Brian,
It’s possible that something changed as the F2 and F4 modems used a radio from a different vendor than the h5 modems. If you still have the source code for the custom application, could you try making the application force the RTS signal on, then see if you can then read data back from the modem? If this doesn’t help, I suggest opening a support ticket, include a description of the custom application including any initialization commands the application sends.
John GawelI am having the same problem. I can manually enter commands using Putty or another terminal application, but my custom C code that worked fine with the F4 doesn’t work with a MTC-H5-B01.
One example, when I type in the command AT+IPR? in PuTTY, it properly returns the baud rate.
But when sent from my custom application, the modem returns garbage characters
Lonny KnudsonHi John,
The most common cause of reading garbage back from a serial port is serial port parameter mismatch. The first thing that comes to mind, if I remember correctly the F2 and F4 series modems shipped with autobaud enabled (+IPR=0). The -H5 modems are set to 115200. Is it possible that you had putty set to 115200, but your custom application was setting the serial port to a different rate?
brian kuslerSorry for the long pause but this got put on our back burner for a little while and we just now revisited it. After an entire Saturday of poking this with a stick the problem actually appears to have been line feeds.
The F4 happily accepts an LF as the command terminator, the new modems do not. issuing the ATS3=013 command to the modem fixed the problem. I hop this helps others!