I won't call this a bug - yet.
I've done quite a lot of work with motion sensors in B4A - amongst other things developing a pretty sophisticated sensor fusion engine that works a treat.
I'm starting to port it to B4i and am playing around with the Motion object.
I have taken the sample from:
https://www.b4x.com/android/forum/t...on-and-acceleration-with-motion-object.49305/
and have goosed it up a bit to include the magnetometer - very simple stuff (zip at bottom):
When I run this I get a screen that looks as follows:
Yet when I run a simple little magnetometer app from iTunes I get:
I believe the iTunes app because part of a diagnostics panel in my B4A app - taken at the same time as the other images (with both phones similarly oriented but well apart), in part shows:
Note the 2 red boxed areas:
The top one is the raw magnetometer values (calibrated for device bias) - they reasonably tally with the iTunes app (see little comparison table at bottom).
The lower boxed area compares measured magnetic intensity and inclination (computed from the raw values) with what would be expected by the NOAA model:
http://www.ngdc.noaa.gov/geomag/WMM/soft.shtml
Comparison of raw magnetometer values:
goosed B4i: 59.5 64.5 -101.1 giving total intensity of 133.9
iTunes app: -19.8 17.2 46.6 giving total intensity of 53.5
....B4A app: -16.4 18.5 48.3 giving total intensity of 54.2
........NOAA: expected total intensity of 56.9
I've done quite a lot of work with motion sensors in B4A - amongst other things developing a pretty sophisticated sensor fusion engine that works a treat.
I'm starting to port it to B4i and am playing around with the Motion object.
I have taken the sample from:
https://www.b4x.com/android/forum/t...on-and-acceleration-with-motion-object.49305/
and have goosed it up a bit to include the magnetometer - very simple stuff (zip at bottom):
B4X:
'Code module
#Region Project Attributes
#ApplicationLabel: B4i Example
#Version: 1.0.0
'Orientation possible values: Portrait, LandscapeLeft, LandscapeRight AND PortraitUpsideDown
#iPhoneOrientations: Portrait
#iPadOrientations: Portrait
#End Region
Sub Process_Globals
Public App As Application
Public NavControl As NavigationController
Private Page1 As Page
Private mot As Motion
Private timer1 As Timer
Private bbStart, bbStop As BarButton
Private Label1 As Label
Private lblAccX As Label
Private lblAccY As Label
Private lblAccZ As Label
Private lblMagX As Label
Private lblMagY As Label
Private lblMagZ As Label
Private lblIntensity As Label
Private lblAttPitch As Label
Private lblAttRoll As Label
Private lblAttYaw As Label
Private MaxX, MaxY, MaxZ As Double
End Sub
Private Sub Application_Start (Nav As NavigationController)
NavControl = Nav
Page1.Initialize("Page1")
Page1.RootPanel.LoadLayout("1")
NavControl.ShowPage(Page1)
mot.Initialize
timer1.Initialize("timer1", 100)
bbStart = Page1.TopRightButtons.Get(0)
bbStop = Page1.TopRightButtons.Get(1)
End Sub
Sub Page1_BarButtonClick (Tag As String)
If Tag = "Start" Then
timer1.Enabled = True
mot.Start
mot.StartMagnetometer
Else
timer1.Enabled = False
mot.Stop
mot.StopMagnetometer
End If
bbStart.Enabled = Not(timer1.Enabled)
bbStop.Enabled = timer1.Enabled
End Sub
Sub Timer1_Tick
Dim attitude() As Double = mot.GetAttitude
Dim SFE_raw_accel() As Double = mot.GetUserAcceleration
Dim SFE_raw_magnet() As Double = mot.GetMagnetometer
lblAttYaw.Text = "yaw: " & NumberFormat(-attitude(0) * 180 / cPI, 1, 2) & Chr(0xB0)
lblAttPitch.Text = "pitch: " & NumberFormat(-attitude(1) * 180 / cPI, 1, 2) & Chr(0xB0)
lblAttRoll.Text = "roll: " & NumberFormat(attitude(2) * 180 / cPI, 1, 2) & Chr(0xB0)
MaxX = Max(MaxX, Abs(SFE_raw_accel(0)))
MaxY = Max(MaxY, Abs(SFE_raw_accel(1)))
MaxZ = Max(MaxZ, Abs(SFE_raw_accel(2)))
lblAccX.Text = "x: " & NumberFormat(SFE_raw_accel(0), 1, 2) & " max (" & NumberFormat(MaxX, 1, 2) & ") G"
lblAccY.Text = "y: " & NumberFormat(SFE_raw_accel(1), 1, 2) & " max (" & NumberFormat(MaxY, 1, 2) & ") G"
lblAccZ.Text = "z: " & NumberFormat(SFE_raw_accel(2), 1, 2) & " max (" & NumberFormat(MaxZ, 1, 2) & ") G"
Try
lblMagX.Text = "X: " & NumberFormat(SFE_raw_magnet(0), 1, 4)
lblMagY.Text = "Y: " & NumberFormat(SFE_raw_magnet(1), 1, 4)
lblMagZ.Text = "Z: " & NumberFormat(SFE_raw_magnet(2), 1, 4)
'Calculate actual magnetic field total intensity
Private Mag_totalintensity As Float = Sqrt(SFE_raw_magnet(0)*SFE_raw_magnet(0) + SFE_raw_magnet(1)*SFE_raw_magnet(1) + SFE_raw_magnet(2)*SFE_raw_magnet(2))
lblIntensity.Text = " Intensity: " & NumberFormat(Mag_totalintensity, 1, 2)
Catch
End Try
End SubWhen I run this I get a screen that looks as follows:
Yet when I run a simple little magnetometer app from iTunes I get:
I believe the iTunes app because part of a diagnostics panel in my B4A app - taken at the same time as the other images (with both phones similarly oriented but well apart), in part shows:
Note the 2 red boxed areas:
The top one is the raw magnetometer values (calibrated for device bias) - they reasonably tally with the iTunes app (see little comparison table at bottom).
The lower boxed area compares measured magnetic intensity and inclination (computed from the raw values) with what would be expected by the NOAA model:
http://www.ngdc.noaa.gov/geomag/WMM/soft.shtml
Comparison of raw magnetometer values:
goosed B4i: 59.5 64.5 -101.1 giving total intensity of 133.9
iTunes app: -19.8 17.2 46.6 giving total intensity of 53.5
....B4A app: -16.4 18.5 48.3 giving total intensity of 54.2
........NOAA: expected total intensity of 56.9
Last edited:
