Hi. Here is the detailed procedure for upgrading the Here+ v2. The guide on ardupilot.org will be updated soon.
Here+ V2 Firmware Update
Tools： Here+V2 ROVER, UART-USB converter, cables, hexagonal screw driver
Connect the cable with UART-USB converter. Connect the red wire to 5V pin and black wire to GND pin.
Remove the cover of Here2+ with hexagonal screw driver (You have to press and hold to remove the buckle). Then replace the cable.
Plug the connector to the computer USB port. Check if all drivers are ready in device manager. If not, drivers can be downloaded here: link to download connector driver
The correct driver should be “USB-SERIAL CH340(COM#)”
“#” is the corresponding port number.
Open u-center and select the COM port for connector. Set the baud rate to 9600 then connect.
After connection, select “Tools>legacy firmware update” to enter firmware update UI. Check the option “USB alternative update method” and select the firmware to be updated. (firmware for here+ and here2+ are the same, please look for detailed procedures from the here+ update procedure). Click OK to begin update.
Wait for the progress bar to finish. If the window turns green, update is successful.
If connection failed after the update window shows up, please change the baud rate to 115200 then update it twice (it maybe still failed at the first retry so please retry it twice).
Hope this will help you.