I've used my NanoVNA-H4 periodically for several years. Yesterday I charged it, then upgraded the firmware from NanoVNA-H4-SI_20211230 to NanoVNA-H4-SI_20211230. I re-calibrated and started doing some testing with it apparently working fine. I got distracted for a few minutes, and when I checked the screen was black. I powered it off, then back on, but the display only appeared for a second, then went black.
Since then when I turn it on I see a normal display for approximately one second, then it apparently shuts off.
Things I've tried, none of which have made any difference:
* Charging it, including overnight.
* Powering it on while plugged into a charger or USB port.
* Disconnecting the battery for a while, then reconnecting it.
* Powering it from USB with the battery disconnected.
I wanted to try re-flashing old firmware, but it appears to do the same thing in DFU mode. When I power it on while holding the multifunction switch, I see the following in dmesg on Linux, and dfu-util doesn't see it:
[385834.014786] usb 1-3.4: new full-speed USB device number 39 using xhci_hcd
[385834.104077] usb 1-3.4: New USB device found, idVendor=0483, idProduct=df11, bcdDevice=22.00
[385834.104090] usb 1-3.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[385834.104096] usb 1-3.4: Product: STM32 BOOTLOADER
[385834.104101] usb 1-3.4: Manufacturer: STMicroelectronics
[385834.104105] usb 1-3.4: SerialNumber: 205E33642031
[385835.056995] usb 1-3.4: USB disconnect, device number 39
Any suggestions of other things to try?
Thanks,
Jim
