Maybe we have to go “on topic again” 
no need to use salt on my open wound 
Yes sir!
@ Brett -
@ Gus -
Yes. We wrongly downgraded EMX to Embedded Master firmware & TinyBooter.
Now seems TinyBooter could be upgraded/downgraded and the device communicates with tera term. But believe the USB part of the EMX is not lighted by TinyBooter now, because the device never refreshes if I replug the USB cable. Is it possible to write a new TinyBooter to enable USB circuit on EMX devices?
You really can’t break the device by loading the wrong firmware. You can always go into GHI loader and erase all using E command.
Problem occur only if one tried to “pirate” the device.
@ Gus -
Now we still could use E command to erase and use X command to upload tinybooter. But there is no response in USB part if I replug the cable. Could you please do a test on EMX by the following steps:
- Upload Embedded Master tinybooter
- Upload Embedded Master firmware
Then see if you can upload 4.x to EMX again.
Thanks & Best Regards!
There is no such thing as an “Embedded Master” firmware though, is there? The EMX firmware from 4.1 would work on an EM, but I can’t remember seeing an explicit 4.1 EM firmware ever. I know that support for the EM specifics was NOT moved forward into the EMX 4.2 firmware. When I look at the latest 4.1 SDK, I can only see a PDF describing the EM to EMX transition, and a readme telling me to use the EMX firmware, there is no sign of anything like an EM specific firmware.
So is it safe to say that you have EMX devices not EM devices? If so, then you can use ANY of the EMX firmwares you like, as Gus says. The next thing you need to do is understand why the USB driver is not loading or detecting the device - this is likely to be something related to your PC