Power Supply Suggestions


#1

I would like some suggestions on COTS supplies that work well the VIM2 using the USB type c connector

I have have 3 usb AC-DC convertors I’ve been trying to power the VIM2 with and have had mixed luck.

Amazon Charger - Runs but when I turn on WIFI in Android the board shuts down.
Google Pixel Charger - board doesn’t even boot up
Old Ipod Charger - board works but shuts off when I have an external drive attached and try to access something.


#2

Hi, maredsous10:
Can you provide the specs for each DC adapters?

Basically, 5V/2000mA+ is recommened for VIM2.

Enjoy!


#3

Thanks. I just ordered a Khadas PSU from gearbest.

Any idea why a Google Pixel charger wouldn’t work? It’s rated at 5V/3.6A I believe.


#4

I guess some adapters spec as Quick-Charge, no sure if the adapters will check hardware model first before working.

Does the Google Pixel charger works fine to other devices? (Except VIM2 and Google Pixel Phone)


#5

I’m not an expert in this field, but AFAIK the latest USB Type-C PD specification includes a negotiation between the charger and the device, in order to set the proper current intensity. That’s because the spec can provide up to 5V 20A (that is, 100W), and at the maximum it would fry a small device and its battery. On the other hand, a small current that can be appropriate for a phone (e.g. 1.5A) would make a bigger device take too long to charge.

So my guess is that, since the VIM2 does not implement that negotiation, but only uses the Type-C port as a plain power connector (like a barrel jack would do), then some “smart” chargers will simply not provide any current, and maybe others will just default to the minimum or to any other pre-set current.

More info: https://www.digikey.sg/en/articles/techzone/2017/mar/designing-in-usb-type-c-and-using-power-delivery-for-rapid-charging
https://www.pcworld.com/article/3017182/hardware/usb-c-charging-universal-or-bust-we-plug-in-every-device-we-have-to-chase-the-dream.html


#6

The interesting stuff starts around page 45.

TL;DR: An USB-C charger is not allowed to exceed ‘default USB power’ if the device at the other end of the cable is not able to negiotate the need for higher current (see page 50 above). Vim2 seems not to implement this (so not getting more than 500mA or 900mA is the only reasonable choice with a real USB-C PSU) and the PSU sold on Gearbest seems just to be a dumb one simply providing up to 2A.


#7

Anyone know if it’s possible to make the vim2 negotiate a higher current? With a kernel or firmware patch I mean. Is the hardware there?


#8

Hi, abliss:
Can you specify more details on this?

Thanks!


#9

well, as tkaiser said above:

I am wondering if it’s possible for the VIM2 to negotiate with a “smart” power supply to be able to draw more than 500mA or 900mA over its USB-C connector.

The first thing I noticed when I started looking around is:


CONFIG_USB_DWC_OTG_HCD=m
But, although I installed the ubuntu 4.9.40 image from the khadas website, it does not seem to include this module in /lib/modules/. So my first thought is to try compiling and loading that module and see if it might make a difference in the ability of vim2 to draw 1A+ from a smart power brick over USB.