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Failure to enter command mode on SX 20mW unit

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Hi all, I am using the new Xbee SX 20mW modules to set up a network. We have one that has entered a strange state (It may have been due to buffer overun issues whilst issuing AT commands causing odd data to be sent). Anyway the issue is that I wish to issue an ATRE command but cannot get it to enter command mode.

The reason seems to be that it is spitting out ff characters constantly as soon as it powers up. This ( I think?????) is dominating the communications lines and preventing the +++ command from being executed.

I have tried minicomming into it and issuing the +++ command, I have tried XCTU and board repair (it reports no bootloader found), I have tried a reset by connection from reset to ground and then upload +++ but I am not quick enough. I have also tried putting pin 4 (DIN) to VCC on power up to try to enter command mode as per the manual. None of these methods is working for me.

Does anyone have anything else I can try to enter command mode, send the ATRE command and get the unit back under control? Would writing a script to bombard it with +++ and wait commands work?

Also does this sound like I have identified the issue that is causing command mode not to be entered or am I missing something more obvious or silly?

Thank you all for your help in advance!
asked Sep 6, 2016 in DigiMesh Proprietary Mesh Networking by simonpearce New to the Community (0 points)

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1 Answer

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Sounds like you are stuck in a bootloader state. All you can do is to try and send it new firmware file to the radio using the recovery method in XCTU.
answered Sep 6, 2016 by mvut Veteran of the Digi Community (11,393 points)
Thank you so much mvut for the quick answer. I'm definitely going to have an issue here then as the castellated board is soldered into our IoT unit. The connections are power din, dout, sleep and the indicator lights. I've been trying to use XCTU to update the firmware but it's not being recognised. It's trying to communicate via an ftdi chip to ATMEGA then out to XBEE (there's no way to bypass this). Hey ho maybe it's unrecoverable, I'll keep trying but at least I know what it is. Once again thank you for the quick response, it's saved me a lot of head scratching. Also I think you answered one of my questions before on lack of comms between Xbee and ATMEGA on our v1 boards. It did end up being the power issue for the ftdi chip etc, we upgraded the voltage regulator and hey presto we now have comms.
Many thanks
Simon Pearce
XCTU needs to have VCC, GND, DI, DO, RTS and DTR connected from the PC to the radio in order to recover it.  Your only other option is to try following the directions in the manual for preforming an OTA upgrade on it.
Hi MVUT, I had a wee brainwave the other night and soldered jumper wires to the castellations, modified an FTDI cable and hey presto the unit is back up and running! XCTU managed to do the board repair and put new firmware onto it. Sometimes just sitting and thinking about ways round the issue is enough. These Xbee's are brilliant little radios and it's good to have solved the issue, another thing learnt and another problem tackled. Cheers once again for the help!
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