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Re: [Paparazzi-devel] apogee board 2.0 - feature questions

From: Gautier Hattenberger
Subject: Re: [Paparazzi-devel] apogee board 2.0 - feature questions
Date: Mon, 12 Oct 2015 22:23:37 +0200
User-agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.8.0


As a side note, I would suggest to remove the RTC backup capacitor to save some space on the board. The clock is set using the GPS time and the backup is used to set the time and date of log files. So having a backup is only needed if you fly without GPS not too long after having a GPS fix in a previous flight. Worse case, the date of your log file is wrong. Even this could be fixed with some messages from the ground station to have an approximate time.


Le 12/10/2015 17:59, Jan Čapek a écrit :

thank you for the feedback, please, see my further comments below
On Mon, 12 Oct 2015 16:44:04 +0200
Michel GORRAZ <address@hidden> wrote:

Hello Jan

- IMU will be updated with MPU9250. This will eliminate need for an
   external magnetometer

Apogee v1.00 is MPU9150 compliant (it includes a _crappy_ mag) but
using a MPU9250 is a good idea.
If possible, put the 9250 as far as possible from the switching power
Good point here, too, not sure if there is space on the board for this
to be moved. Let's see what we can do here.

- SD card sold is discontinued, and will be replaced by the one
   currently in production by molex

New Molex ref is 503182-1853 (exact replacement of 503182-0853)
Yup, this one will be used instead.

- mounting holes - we find the 1.8mm holes pretty difficult for
   mounting the board. The holes will be changed to 2.5mm

v1.00 holes are 2mm, if you really want to increase the diameter, use
3mm, easier to find than 2.5mm
You are right, however 3mm holes already seem to leave too little
material on the edge of the PCB. We will consider that, too.

- servo connectors - we would like to turn the 3 pin connectors 180
   degrees, so that pin 1 corresponds with servos signal. This will
make the board consistent with the standard molex 1.25->futaba/JR
harness cables

For some historical reasons, GND is always on pin 1 of all
connectors, so doing this you will be hobbyking compliant but not
pprz anymore (hello magic smoke)
You better buy a tool to swap the hobbyking's harness molex pins :
I am aware of this, swapping is not a problem. However, a regular user
may not notice that reverse layout. Magic smoke won't happen
in either case since the power+ is always in the middle, in the worst
case you would just ground the servo signal. We will consider your

- power connector - we find the power connection to the board a bit
   difficult without a proper connector. The 4mm connectors (the
distance between the 2 pads) are rather too big for such a tiny
board. We will place a 4 pin 1.25mm molex blade header - pins 1,2
as Vdd+, and pins 3,4 as GND. This will still leave the option to
solder wires directly to the board.T

Don't forget the current of the entire aircraft (servos, modem,
GPS...,) will go through your tiny 1.25mm Molex (0.8A max with 32AWG
That is why we would use 2+2pins. Anyway, I will consider if there are
other options for the connector.
Good luck for routing ;-)
Thank you for all the valuable comments,


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