Author Topic: WiFi Dongle issues - Massive Current spike  (Read 4521 times)


WiFi Dongle issues - Massive Current spike
« on: September 28, 2015, 12:03:02 pm »
One of the members who had reported an issue with his WiFi dongle was kind enough to exchange with one of mine so I could investigate. I have discovered a very interesting piece of behavior

The Dongle in question reported as a Ralink RT5370 from the PiHut

I attached my USB meter which monitors peak V/A information.
When the PiHut dongle is configured as a Soft AP so that it can behave as an Access Point, there is a current
spike of 720mA
This is the cause of the bad behavior !

The RPi B+ by default, will only accept a current draw of 600mA from its USB ports.
This spike causes a soft reset of the USB ports, and hence the problem.

By comparison, the RT5370 devices I have been purchasing have a peak current usage of 270mA
well within the limits.

It is possible to reconfigure the PI to accept 1.2A on its USB ports, but this current draw I have observed
using these dongles, is ridiculous. So now I wonder how many other dongles have a similar issue regarding the
peak current usage ?


Re: WiFi Dongle issues - Massive Current spike
« Reply #1 on: September 28, 2015, 01:06:26 pm »
I think it might be worth making a list of known good hardware (and suppliers of such) for all the component part of a PA and encouraging purchase of those only (based on those of us successfully building).

Predictability of builds is probably more important than wide-variety of supported devices - you have more than enough on your plate already Lee!
I guess it's also the way forward in terms of settling on a "kit" PA and maybe even PA complete unit production ?

IMHO stability of the hardware and take-up of PA boxes by pilots are the keys things in the big picture of PA becoming a widespread success.
With the USB GPS support and the baro sensor support (great work thanks  ;D) now there, do you think you're close to the point of minimal hardware change Lee ?

Software enhancements and more wide-ranging component support could come later ? Just my 2p.

Meanwhile am building 2 more PA boxes for people that have asked me now the ARF supply is back!  :) 8)
I wonder what WirelessThings plans are regarding manufacturing now they see a strong demand for it!


Re: WiFi Dongle issues - Massive Current spike
« Reply #2 on: September 28, 2015, 01:24:05 pm »
I changed the setting in config.txt to "max_usb_current=1" but there was no change in the performance of my dongles, they still fail.
May be there is another setting I don't have access to.
I will receive one of the dongles supposed to work during the week.