Bricked RTK Express after a firmware downgrade.

[Stefal]

Subject of the issue

For some tests about #733 I've downgraded a brand new RTK Express from 3.8 to 3.7. Since then, I can't use it anymore. The same thing happened with another Express.

Your workbench

• What version of RTK firmware are you running? 3.7

Steps to reproduce

Downgrade from 3.8 to 3.7

Actual behavior

The flashing process was successful. Now when I power up the Rtk Express, it starts, display the firmware number briefly, then power down.

I've tried :

• Serial Usb connection / flash tool, but the CH340 device disappears too fast.
• Press the power button for more than 10 seconds
• Put a firmware release named RTK_Surveyor_Firmware_Force.bin on a micro-sd card. The RTK Express starts to flash the firmware until 5% then power down.

Is there a safeboot or something else to try to reflash these 2 RTK Express ?

[nseidle]

Before you follow the instructions below, what is the display showing when the device is powering on? 'RTK Facet' or 'RTK Surveyor'? I've got a hunch about the ID resistor causing problems.

They are always recoverable, it just gets tricky.

Please see the StayOn firmware. Use the esptool CLI to 'catch' the device and program the stayon.bin while it is booting RTK Firmware. This takes a bit of practice to power on the device and then press return on the CLI while the COM is open. Once stayon is loaded, it's just a dumb ESP32 that won't power up or down. You can force power off/on the device, but the ESP won't try to power the device down.

From there, you can program any firmware you'd like.

[Stefal]

Thanks, you were right, the display was showing "RTK Surveyor".

I've used StayOn firmware, and I've had successfuly flash the devices with a working firmware >= 3.8. Previous firmware didn't work (RTK Surveyor diplayed, then power down).