Turn screen on and off over BLE

[FedericoCeratto]

Hello and thanks for developing the firmware.
I would love to be able to turn the screen on and off remotely over BLE on the RISC-V variant. Ideally the off state should be really low power.

[kienvo]

Hi @FedericoCeratto, thank you for the interesting idea.

Currently, the BLE is only turned on in the download mode. To have this feature implemented, I think we should change a bit how BLE works:

• Defining new characteristics/services and data exchanging around these so we can send on/off commands over the new characteristics.
• The badge will have always-on-BLE, probably consume more power (I haven't do the measurement yet), but I think we could turn it on/off over the characteristics above.

For low power sleep while BLE is turned on, I haven't figured out how it works on this chip. The datasheet is missing the BLE sections. The internal clock source for BLE seems noisy. All my works on BLE are guessed based on BLE conventions =]