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Good Morning,

i'm trying to work out the reason to weird characters being outputted in a serial console in linux.

Device: 12d1:15c1 Huawei me906s module in a WWAN to USB adapter (working for normal operations and switches modes etc

The device is connected initially with the PID 15c1 and the output of lsusb -v below: 12d1:15c1 Output

When the device is sent the AT Command of AT^GODLOAD, it switches into download mode which changes its PID too 1568. Output of lsusb -v below:

12d1:1568 Output

OS: Ubuntu 16.10

Speed: 9600 baud as reported by stty -F /dev/ttyUSB0

Expected: Send AT Commands through /dev/ttyUSB0 with minicom or echo/cat Result and Description: When the device is in normal mode (15c1) the device ttyUSB0 is used to send AT Commands, this works perfectly and we can set the chip into download mode (PID 1568)

After Download mode is enabled the chip reboots and reconnects too ttyUSB0, however weird characters show up in minicom and through terminal using 'cat

The weird characters are the same in both monitors and the hex is: 7e 03 00 06 9e 4c 7e

When we send any AT command in download mode the characters show up, except for one AT command as shown in the pictures. This command is significantly larger than any other ones.

Command examples which don't work in GODLOAD:

AT+CMGR? ATI -Results in the weird characters ~[][][][]L~

Command which does work: AT^SIGNVER=5,0,1234567891011121314151617181920, 8502

We have used wireshark to capture the update process on a windows machine.

I actually have screen shots of the operation, commands etc but cannot post them due to limit.

Questions:

-Does the packet size matter for serial commands sent to the module? -Are we missing some form of a line ending, carriage return or termination to start/end the message correctly?

Thanks for your help in advance

microleb
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    That looks like a binary packet of some sort - 7E is the packet delimiter, 03 is the length, 00069E is the payload, 4C is the checksum. (Or perhaps the length is two bytes long, and there is no checksum.) Are you sure that the device is even supposed to respond to AT commands when in download mode? – jasonharper Aug 15 '17 at 04:41
  • we presume it does, as the wire shark output has it still sending at commands to the module whilst in GODLOAD mode, and the other command works, but the others don't. To summarise it basically does this process: -Bunch of checks -GODLOAD -SIGNVER -Bunch of other at commands -Updates FW -Resets back to Modem mode. – microleb Aug 17 '17 at 06:10

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