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[Paparazzi-devel] re:RazzorIMU


From: GARCIA ALVAREZ, ANA
Subject: [Paparazzi-devel] re:RazzorIMU
Date: Thu, 10 Feb 2011 13:40:47 +0100

Dear Dr. Warmers,
I have finally installed Oliver's software version. I had a compiling
error related to an AHRS_ALIGNER_led and have solved it after defining
it in the makefile for my board(tiny v2.11). 
Now I can see the PFD running, but don't know if it moves in the usual
way. It has a slow rensponse and a little oscillatory. 
Ana

-----Original Message-----
From: GARCIA ALVAREZ, ANA 
Sent: Thursday, February 10, 2011 10:58
To: 'Prof. Dr.-Ing. Heinrich Warmers'
Subject: RE: RazzorIMU

Dear Dr. Warmers,
I have been looking in this code, although I'll look again. Sorry I'm
asking too much, but am not very experienced in programming and looking
into the code is a bit hard for me. 
Ana

-----Original Message-----
From: Prof. Dr.-Ing. Heinrich Warmers [mailto:address@hidden 
Sent: Thursday, February 10, 2011 10:51
To: GARCIA ALVAREZ, ANA
Subject: RazzorIMU

Dear ARCIA ALVAREZ,

Please look in the branch
of oliver and crihstoph
http://paparazzi.enac.fr/wiki/User:Christoph

Pleas note that Christop has put the imu in the opposideed direction 
compared to Oliver.
Olivers code is running on a tiny and chistorp on a tworg.
Regards Heinrich



Hi Ana, Hi Felix, Hi Heinrich,

the SENS values in hb_tiny_razor.xml airframe file (4096 = 12 Bit) are 
only set to reverse the BFP
formating what ist done for rates in RATES_FLOAT_OF_BFP(gyro_float, 
imu.gyro); in ahrs_propagate();

/* convert bfp imu data to floating point */
RATES_FLOAT_OF_BFP(gyro_float, imu.gyro); // olri div by (1<<12)

/* unbias rate measurement */
RATES_DIFF(ahrs_float.imu_rate, gyro_float, ahrs_impl.gyro_bias);

The trick to get it work is to scale the values from deg/s to RAD/s,
see the lines below from my ahrs_propagate();.

// scale gyro adc raw to [rad/s] FIXME // olri
ahrs_float.imu_rate.p /= 61.35f;
ahrs_float.imu_rate.q /= 57.96f;
ahrs_float.imu_rate.r /= 60.10f;

The result of the that *must* give closest-by 0.0... rate on silence!

It's at the moment *impossible* to combine these 2 factors,
becourse the bias is substracted between these to steps.







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