Yep, it's a button
Cheers.
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Daniel
As previously linked to by someone else, here is a link to W4KWS's video of OpenGD77 on his new UV390 Plus
I tried three times to upload different version of firmware. All I get - dark screen, and few morse sound. I'm already have OpenGD on DM1801, so updating process is not a problem. I think it's because there are more than one version of firmware (and hardware) for Plus version. For example:
There is a report in this other thread that pushing PTT button wakes the screen - does that happen for you as well?