I assume that by default any Shimmer axes should correspond to how they are
depicted in figure 1 on page 6 of the 9DOF user manual. Meaning, if one does
not apply any correction to the raw data the Acceleration and Gyro axes are as
they are displayed.
With that said, if I am not going through the calibration process in 9DOF
utility, I am just using the utility to see the steam of acceleration or
gyroscope data, does this utility still applies some transformation on the raw
data?
If the answer is yes, then this may be the reason why 9DOF real time display
shows the axes as they are depicted in the figure and JustFATLoggin does not.
Is there a utility that does just stream the raw data?
In JustFATLoggin theGryo data does not agree with 9DOF on the X and Y axes. And
the acceleration in JustFATLoggin X and Y axes are as depicted in the figure
(and this matches 9DOF real time display), but the Z axis is reversed.
Rahav Dor
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From: "[email protected]"
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To: [email protected]
Sent: Friday, August 31, 2012 11:00 AM
Subject: Shimmer-users Digest, Vol 65, Issue 12
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Today's Topics:
1. Re: JustFATLoggin axes vs Shimmer 9DOF (Chris B)
the 9DOF calibration utility applies an alignment matrix to the decimal output
(along with the scale factors and offsets). The alignment matrix contains axis
order and sign, as well as any non-orthogonal corrections. JustFATLogging just
outputs the decimal data as is, as far as i am aware, so you would need to
apply the calibration coefficients to gain calibrated output with the correct
axis order/sign. Take a look at the Calibration Utility manual.
Chris
________________________________
Date: Thu, 30 Aug 2012 07:17:18 -0700
From: [email protected]
To: [email protected]
Subject: [Shimmer-users] JustFATLoggin axes vs Shimmer 9DOF
I've modified JustFATLogging and the Shimmer provided MATLAB code to collect
Gyro readings. I added the Gyro using:
call GyroInit.init();
call GyroStdControl.start();
call shimmerAnalogSetup.addGyroInputs();
For debugging I decided to compare the data collected by JustFATLogging and
Shimmer's 9DOF Calibration utility. It seems that when I position the Shimmer
on its face (logo side) JustFATLogging thinks that it is the -Z acceleration
axis (9DOF correctly shows that it is the +Z).
When I check the gyro is seems that JustFATLogging and 9DOF do not agree on
which is the X and which is the Y axis.
In MATLAB I am reading the data by:
sensorsData = fread(fid, [NUMBER_OF_CHANNELS,Inf], 'uint16');
accelx = sensorsData(1,:);
accely = sensorsData(2,:);
accelz = sensorsData(3,:);
gyrox =
sensorsData(4,:);
gyroy = sensorsData(5,:);
gyroz = sensorsData(6,:);
What am I doing wrong?
Thanks,
Rahav
Rahav Dor
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