Flash:
@Paul, i think we can replace all the delayMicroseconds in that lib with faster delays - but, maybe, this needs some testing with other chips ?
Edit: just tested it with with the W25Q64FV. Indeed, it works.
The Datasheet mentions a delay of 5 ns "relative to clk" - with SPI @ 30MHz a clk is 33ns.
FWIW, I re-ran my SerialFlash tests on prop shield with teensy 3.1 @120mhz and experienced no problems ...
mortonkopf thanks!@defragster, yes, particularly the APA102 leds (Adafruit calsl them dotstar). . . .
Magnetic TestBegin FXOS8700
id = C7
FXOS8700CConfigured
FXOS8700: -10.20 -6.40 78.00
FXOS8700: -9.60 -24.90 59.80
FXOS8700: 1.40 -37.70 70.20
FXOS8700: 2.50 -19.10 96.10
FXOS8700: 7.80 -40.70 91.20
FXOS8700: 2.90 -17.40 104.00
FXOS8700: 10.90 -17.90 97.20
FXOS8700: -7.10 -14.50 81.00
FXOS8700: -12.10 -13.70 60.10
FXOS8700: -5.80 -33.20 64.90
FXOS8700: 2.10 -35.50 86.30
FXOS8700: 5.50 -16.50 103.10
FXOS8700: -24.40 -49.70 101.80
FXOS8700: -34.70 24.70 97.30
FXOS8700: -54.00 48.40 108.60
FXOS8700: -81.30 149.10 168.20
FXOS8700: 86.20 18.60 302.50
FXOS8700: 81.30 28.70 301.20
FXOS8700: 43.40 96.50 270.80
FXOS8700: -25.10 167.90 84.00
MPU9250magCalibration[3] = {0, 0, 0}; // Factory mag calibration and mag bias
Mag Calibration: Wave device in a figure eight until done!
Mag Calibration done!
Mag Cal_d1:0.00
Mag Cal_d1:0.00
Mag Cal_d1:0.00
__________Mag Cal_d2:0.61
__________Mag Cal_d2:1.71
__________Mag Cal_d2:1.30
Yes, a extended kalman filter is needed, as the angualar movement introduces nonlinearity. However...A kalman filter should be used to keep track of heading. This will automatically compensate for errors.
...You are correct about the gyro and magnetometer part, but "Accelerometers are accurate in the long term" would mean they had no offset and zero drift. To my understanding accelerometers are like gyros as they measure the derivative of the physical state (location and direction respectively). So Accelerometers are the "short term" input for the filter, and GPS would be the drift corrector as it provides absolute position (with great uncertainty, but that's what the kalman filter will take care of). So with the Prop Shield having no GPS, I think it's important to provide a routine to build a calibration table at least for the accelerometer, preferably at several different temperatures, to compensate offset and drift as good as possible.Accelerometers are accurate in the long term
Gyroscopes in the short term
The magnetometer will correct the drift