Charging

On A780 and E680, (maybe on other gen1 devices): The BP control the battery, so we need to send this "magic" AT command to enable the charging:

(tested only to charge over the USB cable)

echo -e "AT+USBSTAT=255,1\r\n" > /dev/mux4

On gen2 devices, the PCAP2 chip is controlling the charge, there are patchs to come that will handle this.