HK3 ACC Hardwire Kit - communication with A119 V3 ?

[triodak]

On main Viofo page I asked about:
Q: How does HK3 ACC inform DVR to activate parking mode? Does it send special data packets over USB data line to DVR to switch to parking mode?
A: It detects the voltage using the ACC cable.

Unfortunately this answer does not dispel my doubts.
I know that HK3 senses voltage (analog value) and ignition status (on or off). But this power supply converts voltage to 5V DC for A119 V3 and deliver it through 5 pin mini-B USB plug.

How A119 V3 knows that ignition is off? (HK3 knows about it from ignition status and may know from voltage value) There are two possibilities:
1. HK3 send special packet of data to A119 V3 over USB data lines.
2. HK3 give on PIN 4 (ID pin) either ground signal (instead of open circuit) or it put certain voltage value on that pin.

From my point of view those two possibilities are the only one.
Question is what is used by HK3 to inform about ignition status?

Second question:
Does "instant switching to parking mode" in A119 V3 after ignition is off works when HK3 is connected to GPS base (not directly to A119 V3 unit)?
In other post we can read that in 129 Duo HK3 need to be plugged directly to car dvr for proper working of instant switching to parking mode.

 

[Obi-Wan]

It uses PIN4 (ID) to send ACC signal (but converted 12V -> 5V) to the dashcam. As simple as that, no USB packets there ;-)
Yes, it can be used via GPS module and works the same as directly to the cam.
Checked on FW2.1