Some progress… successfully flashed the JL1 board with Grbl 1.1f (@LsrSal’s ROM.bin file). I use Chromebook/Lightburn almost exclusively but decided to fire up my Win7 machine for the first time in a couple of years. It took a while to update wifi and log into forums. Yuck!
Downloaded @LsrSal’s zipfile and extracted ROM.bin and upgrade.exe files to Desktop. Found instructions from @LsrSal in a different thread to…
- Make sure power is off on JL1 board
- Make sure upgrade.exe isn’t running
- Connect USB cable… computer to JL1
- Push and hold button (between the USB and power connectors) on JL1 while powering it on… puts board in upload mode
- Execute upgrade.exe
A very simple window pops up with one button and progress bar… apparently just defaults to ROM.bin…
Clicked “start upgrading” button and indeed a green progress bar comes up and completes. No messages, status, nothing… but no error indication either.
Since I had previously swapped out the JL1 with a different Grbl controller, I reconnected the JL1 board back up to the laser engraver. Moved over to Chromebook and Lightburn… connected USB and got indication that a USB device was detected and connected to Linux side. In LB I was able to connect and console indicated GRBL 1.1f. It acted a bit flaky at first and kept locking up until I also connected up the limit switches and adjust some settings. It’s now settled into a predictable state and I’m air-milling now under Lightburn control.
So, it looks as though it’s pretty easy to flash that board with a ROM.bin file and the .exe. Hate to have to fire up Windows but, given the tools I had, I guess that was my only recourse. [I now feel a little “dirty” 
] Given the generic filenames, I had no way at first to know for sure what board that ROM.bin was set up for until I finally tamed the erratic operation…
The upgrade.exe appears to do what it was supposed to do.
– David