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Re: [Paparazzi-devel] YAPA2 help needed

From: Chris
Subject: Re: [Paparazzi-devel] YAPA2 help needed
Date: Thu, 09 Aug 2012 21:37:42 +0300
User-agent: Mozilla/5.0 (X11; Linux i686; rv:14.0) Gecko/20120714 Thunderbird/14.0

I think i am on to something.
I remembered that the board worked fine for a day or so when it was powered directly from 4S lipo. Now the only difference is the added 25.2v to 12v psu AND that when i was using 4S the receiver was powered from the onboard 5v regulator (i connected a wire to the 5v psu) not from the BEC as it is supposed to be in YAPA2. Could it be that the PPM signal from the receiver is applied before the LPC gets power ie having a situation where a pin has an input of 5v before the LPC has it's 3.3v and this damages the LPC2148?

From the LPC2148 errata:
On port pin P0.25 (when configured as general purpose input pin), leakage current increases when the input voltage is Vi > Vdd I/O + 0.5 v. Care must be taken to limit the
current to less than 4 mA by using a series limiting resistor.

Strangely P0.25 is the IRH2 analog input which i use for voltage sensing but this input has a 10Kohm resistor so a current of 4ma is not possible but i don't know about the PPM input.
Maybe this applies to other inputs also.
Is this possible (Anyway it is the only thing i can think of so any help or opinion is welcomed)? Also i noticed that the LPC might not work anymore but it is not completely dead, it produces unusually high amount of heat.

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