A329S: Safe to connect phone to side USB-C while powered from GPS mount?

[emprordolan]

I’m using a Viofo A329S and would like to connect my smartphone to the side USB-C (SSD/Data) port for direct file transfer while keeping the camera powered via the GPS mount USB-C (hardwired to the car).

Can Viofo confirm whether the A329S has power-input isolation or PMIC/power-mux protection that prevents back-powering or reverse current when both USB-C ports have 5V present at the same time?
Specifically, is there defined power-priority logic between the GPS mount USB-C and the camera’s side USB-C port?

 

[Anthropos]

I’m using a Viofo A329S and would like to connect my smartphone to the side USB-C (SSD/Data) port for direct file transfer while keeping the camera powered via the GPS mount USB-C (hardwired to the car).

Can Viofo confirm whether the A329S has power-input isolation or PMIC/power-mux protection that prevents back-powering or reverse current when both USB-C ports have 5V present at the same time?
Specifically, is there defined power-priority logic between the GPS mount USB-C and the camera’s side USB-C port?

Here is my opinion:
VIOFO states that the PSSD/SSD is connected to the USB-C (SSD/Data) side of the main unit
The power is supplied by the USB-C of the GPS base
so that they work simultaneously without interference.

This practically means that the company has designed the device for “data/SSD from the side + power from the base”.
Yes: simultaneous SSD on the side + power from the GPS base is officially foreseen.

When there are 5V simultaneously on both ports, the camera usually uses the source that provides the highest/stablest voltage. In most cases (without being ABSOLUTELY SURE), the camera "locks" to the power from the GPS base and uses the side port exclusively for data transfer (Data Link).

Most likely outcome: the mobile phone will not recognize it as a storage.

And if it “shows something”, you can’t rely on there not being a backfeed/current in a strange direction without official confirmation.
Simply put: it most likely will not work as you imagine, even if nothing happens electrically.

 

[VIOFO-Support]

I’m using a Viofo A329S and would like to connect my smartphone to the side USB-C (SSD/Data) port for direct file transfer while keeping the camera powered via the GPS mount USB-C (hardwired to the car).

Can Viofo confirm whether the A329S has power-input isolation or PMIC/power-mux protection that prevents back-powering or reverse current when both USB-C ports have 5V present at the same time?
Specifically, is there defined power-priority logic between the GPS mount USB-C and the camera’s side USB-C port?

There is no need to supply power additionally via GPS port when connecting the camera to your phone.
You can refer to this video:

 

[Anthropos]

The video you sent reinforces that the USB-C side is for direct file transfer with devices like iPhones.

But the hardware does not have an official guarantee that it manages "2 simultaneous 5V sources with power priority".

But in practice, if you have power from GPS/base and data on the side, and a proper USB-C data cable, it usually works without issue.

This does not change the fact that the power path design is not fully documented as priority multiplexing.

That is:
• the power + data connection can be passed in parallel
• also there is no official statement that the hardware controls pre-designed "USB-C power vs side USB-C power supply priority" with backfeed isolation.

------------------------------------
the iPhone (USB-C, especially iPhone 15/16):

Negotiate USB roles (power source / sink / data)

It can:

consider the A329S as an accessory that needs power

or try to supply 5V (reverse power)

or wait for the other device to give it power

Although the GPS base already gives 5V, then:

without documented power-mux / ideal diode / reverse-blocking,

no one can guarantee that there will not be:

backfeed

source conflict

undefined USB role behavior


👉 there is no guaranteed result.

 

[emprordolan]

Thanks @Anthropos — you put very clearly what I was trying to get at, and I 100% agree with your take.

That’s exactly why I asked the question in the first place: not because I assume it doesn’t work in practice, but because from an electrical/design point of view this is an obvious scenario, and I wanted to understand whether Viofo’s developers explicitly considered it and how they chose to handle power prioritization or isolation between the two USB-C ports.

Given the price of the A329S, I’m also not particularly inclined to “just try it” on my own hardware and hope for the best. I’d much rather understand the intended design and power behavior first.

I’m hoping there is a deliberate design decision (power-mux, priority to the mount, reverse-current protection, etc.), even if it’s not documented — it would just be good to have that confirmed officially.

Appreciate you spelling it out so succinctly. 🙏🏻