Random brown outs, screen flickering, and possible solutions

userHead LattePanda 2016-09-02 18:28:33 4810 Views4 Replies
I have been trying to replicate some of the issues posted on the forum relating to random brown outs, i.e shutting off unexpectedly and screen flickering.
Some of these random shutoffs are down to the cherrytrail hitting a thermal threshold and shutting down (an inbuilt safety precaution of the cherrytrail), however, some issues are related to voltage drop as a result of having the 7" screen attached to the mipi connector. obviously as the screen has no external power source it is drawing power from the board itself.
viewing the panda through an hdmi output or a vnc server should not require extra voltage.

here are some experiments i did:

my setup:
using the 7" screen attached to the panda though mipi interface.
I have used a bench power supply and and powering the panda using the CN2 headers using F dupont wires
amp draw is about 0.8a - 1a

NOTE: if you try to replicate this, please note that the panda can handle up to 6v but it is not advisable to go beyond this, *AS YOU WILL FRY YOUR BOARD*

problem: screen flickering
reason: screen is receiving insufficient voltage
solution: increasing voltage to 5.3 - 5.5v has it running stable

problem: lattepanda powers off in bios before booting in to windows
reason: board is not receiving insufficient voltage and browning out
solution: 5.5v - successful boot

problem: windows boots, but browns out when i click start
reason: board is not receiving insufficient voltage as processor voltage spikes and is browning out
solution: 5.5v - ok as long as screen is not at full brightness
if screen is at full brightness, 5.7v has it running stable

conclusion: if you have the screen connected, you will probably need slightly more than 5v

hope this can point someone in the right direction!