Finally - OTG for all without modifying your headunit. With only basic electronic/soldering skills, get OTG and fearlessly flash or recover a 'bricked' Rockchip PX3 or PX5 SOM.
See attached pics for making an OTG cable from a USB cable and two resistors.
Resistors are 12K and 15k (22k is probably better) or anyone of the following. combinations. These resistors are necessary as 'voltage dividers', with a value between 1.8v and 3.3 OK. These simply place a logic '1' on recovery and USB-OTG to 'tell' the SOM to go into OTG recovery mode.
R1 | R2
1K | 1.8K
2.2K | 3.3K
10K | 18K
12K | 22K
Get Windows Driver [Driver assistant v4.5] and [Android tool 2.39] for direct/OTG SOM flashing here.. Be sure to edit [android tool] .ini file to set English, otherwise tool will be rendered in Chinese.
This tool for dumping / getting full backup of SOM
Excellent tool, thanks @RedScorpioXDA
Note - all tools and driver have equivalent Linux versions.
Further Details to follow.
Credit (thanks!) to @scorillo_ro for the detailed image/connections diagram.
Worst case - SOM doesn't respond - force 'maskrom' detailed here explaining what MaskRom is and here on how to for your PX5 (px3 is similar.) Steps are: Power Off SOM and disconnect USB to PC. Use Tweezers, apply power/connect USB. Hold until Windows Device chime is heard (within about 2 seconds of power on.) See attached pic.
Warning : Use thin pins for OTG cable in order to avoid the damage of the SOM connectors, although along the thread it has been noted many times that damage to the SOM socket is very likely to happen if thick pins are used...OR buy SOM header from Aliexpress, digikey etc.[/COLOR]