OpenGD77

Hi to all,


unfortunately due to a faulty cable or USB port, I broke 3 GD77.


I have thoroughly analyzed the fault in the laboratory.
The radios were without signs of life, absorbing about 120milli amps. I found that there was a short circuit on the part of the voltage regulators that powered the MCU.
The short circuit comes from the MK22FN512VLL12 MCU.
With suitable equipment I replaced the MCUs on the radios, the short is gone.
the current draw is currently 0.01 amps (I would say good).

My problem is that I can't go to DFU mode to program the FW OpenGD77, my Windows PC recognizes me connected to a USB peripheral but not as a radio. No led flashes.

I suppose some preliminary programming FW of the ARM MCU is needed, can anyone help me?

Thank you very much a hug
IZ4RCU

If you replaced the whole MCU it will be blank and not contain a bootloader

You'll need to reflash the bootloader by connecting to the JTAG/SWD pins

However, the MCU's also originally get programmed with a hardware key locking system, which the bootloader and the official firmware, check before they run.

Luckily for you, I already extracted the official bootloaders from the GD77 and similar radios and patched them to remove the code that checks the hardware keys

See

https://github.com/rogerclarkmelbourne/ ... ootloaders

Hi Roger, now I think I know why my DM-860 is not working: it has a corrupted bootloader. I've found one of the symptoms as you described here about the green LED not flashing at all.
https://github.com/rogerclarkmelbourne/ ... ootloaders

I'll try to upload it via the jtag connector.
Thank you for the extensive documentation and written material you've produced.

Andrea

M6KDU wrote: ↑

Fri Mar 05, 2021 11:21 pm

Hi Roger, now I think I know why my DM-860 is not working: it has a corrupted bootloader. I've found one of the symptoms as you described here about the green LED not flashing at all.
https://github.com/rogerclarkmelbourne/ ... ootloaders

I'll try to upload it via the jtag connector.
Thank you for the extensive documentation and written material you've produced.

Andrea

OK.

Loading the patched bootloader should do the trick.

Make sure you connect the reset line when you initially reprogram the MK22, as the full chip erase seems to need the reset line as well as the SWDIO and SWCLK