On Sat, 02 Sep 2017 08:54:00 +0000 Joonas Kylmälä <joonas.kylm...@iki.fi> wrote:
> So far I have tried with the non-modified replicant kernel for i9305 > and 150k resistor level. Then I also tried to tweak some configs in > the kernel but honestly I had no clue what I was doing :D The USB connector is connected to a switch which can switch between at least: - An USB OTG port, controlled by the CPU running Android/Replicant - A serial port, also controlled by the CPU running Android/Replicant The idea behind this resistor configuration is to tell the switch, from the outside, to "route" the serial port mentioned above to the USB connector. Some of such switches can also be controlled by software running on the CPU running Android/Replicant. /!\ Some warnings and advises when dealing with switching the USB / ! \ connector to the serial port: -------------------------------------------------------------------- - The voltages levels of the USB OTG port pins (Data+ and Data-, VCC, GND) are at 5V levels. - The voltage levels of the serial port is probably way lower, down to something like 1.8V. => The "CPU" running Android/Replicant probably doesn't support 5V input on its serial port, and if it is the case, it could fry the serial port or even the whole "CPU". => It could also fry the USB<->serial adapter you are using if the "CPU" outputs more than the maximum supported voltage. So it could be a good idea to use an apropriate USB<->Serial port adapter that can deal with such low voltages and has some protection (diodes) against the "CPU" outputing voltages like 5V. Sysmocom or the Osmocom project designed an adapter that has protection diodes, but I am writing this mail offline, and I don't remember: - Which voltages levels it supports - Which voltages levels the Galaxy S3 serial port is at. Denis.
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