Since my last post, my Maple mini clones have arrives and I was able to test whether it was possible to upload via USB to serial.
Initially I found that this could be done, but that it only worked intermittently.
I eventually tracked down the cause of the problem, to the Boot1 line on the Maple mini board, not being tied low. So that when Boot 0 (zero) is pulled high via the “Button”, sometimes Boot1 was floating high.
This cause the board to not correctly enter the Serial upload mode, as Boot1 needs to be low.
The simple solution was to attach a flying lead between Boot1 and Gnd, as Boot1 is available on “pin 2” of the board.
The long term solution however is to solder a 10k resistor between Boot1 and Gnd.
After connecting the wire between Boot1 and GND, uploads became very reliable via USB to Serial.
I also tested the Maple USB upload feature, and this also worked fine under Windows 7 – once I’d rebooted with the Device driver signing requirement disabled.
Unfortunately with Windows 7, every time you reboot, this setting gets removed, so you need to press F8 every time you boot, to enter the Windows boot menu that lets you select the option to disable device driver signing requirement.
I understand that this process is not as bad under Windows 8.1 as the setting is remembered by the OS, however I have not tested this myself.