Thursday, October 27, 2016

Fixing a borked MediaTek LinkIt Smart 7688 Duo

Hardware: MediaTek LinkIt Smart 7688 Duo

Firmware: 0.9.3

NOTE: At this time (10/27/2016) I am extremely dissatisfied with MediaTek's approach to supporting this hardware in the field and find them to be wholly unprofessional. They appear to be hoping that the community will solve all the problems with their software/firmware and are not interested in engaging in anything beyond the simplest configuration questions.
I've had a few of the MediaTek LinkIt Smart 7688 Duo (can we fit a few more words in there) boards get into a bad state during configuration. As a result of this, I've gotten a bit aggressive in not using the GUI configuration items and focusing on the CLI ( for configuration. In fact, the first thing you should probably do once you have configured these is to vow never to use their GUI or the LUCI interface again. It just causes problems.
When configuring these for remote sites it is simpler/safer to have a standard batch file to run and set them up versus leaving it to chance to onsite techs. Eventually, you would want to create your own firmware and boot the boards to that at setup time. Having only started with this board and doing a lot of testing, I've been left with a few boards that no longer function. So I finally dug out the documentation and was able to restore all of them to a functional state. It is pretty simple but it requires patience:
  1. Get an OTG USB micro-USB male to USB female cable
  2. Download the firmware:
  3. Copy it to the root of a FAT formatted USB drive
  4. Power up the 7688 via the PWR/MCU port and let it boot (wait about 2 minutes to be safe)
  5. Plug in the OTG cable to the USB Host port
  6. Plug the USB drive into the OTG cable
  7. Press/hold the MPU and WiFi buttons on the 7688
  8. Release the MPU button
  9. Wait 5-7 seconds then release the WiFi button
  10. Wait...

At this point you can you can just come back in ten minutes or so and start scanning for WiFi signals with your phone or similar. You should see one that is the standard "LinkIt" access point appear and can just disconnect the OTG cable and do the normal process from there. Alternatively you can just stomp on the board and get some immediate satisfaction.

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