This has been one of the most frustrating days in a while…
Here is the short version.
I removed the G120 modules from the boards and wired a usb connector, power + ground + reset, LDR0 and LDR1 pins to a 3.3V power supply. 2 boards worked as expected with the LDR pins grounded and high. The third G120 was dead. I was able to upgrade the G120 to 4.2.10.
Using the same wires I connected the module to my PCB, and was able to upgrade the modules.
Next step was to re-solder the modules to the PCB. I started by soldering only the minimal pins needed for update - this also worked fine.
Then for about 2 hours I soldered pin by pin while checking to see if I can see both virtual com driver and the GHI debugging driver when switching my DIP switch. I was able to solder all the pins and still be able to load both drivers.
After 15 minutes I could not load the virtual com driver on a PCB that worked fine 15 minutes before. The GHI driver loads fine when the LDR pins are high.
I am not sure whats wrong with my board - but at least I can start SW development and show progress.
Is there any power sequence I should look for? timing between VCC rise and reset?
The weird thing is that it worked fine hooked up to a power supply with crocodiles with no decoupling at all and the reset line tied constantly to VCC (maybe I should remove the reset RC filter … )
Ir these any other specific pin I should look at that has a function during boot?