28029 Parallax Inc, 28029 Datasheet - Page 149

• Manufacturer Part Number: 28029
• Description: KIT PARTS SMART SENSORS W/TEXT
• Manufacturer: Parallax Inc

Specifications of 28029

• Accessory Type: Parts Kit
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: BASIC Stamp® or Javelin Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant
• Other names: 28029PAR

' -----[ Subroutine - Compass_Correct_Offsets ]-------------------------------
' This subroutine corrects cumulative magnetic field interference that can
' come from sources such as the PCB, jumper wires, a nearby battery, or a
' nearby current source.
' the EEPROM space that was reserved by the CompassOffsets DATA directive.
' These EEPROM values are written by this program during calibration.
Compass_Correct_Offsets:
Your Turn - Reviewing the Calibration Settings
In the main activity, you typed the letter C to store calibration values in the BASIC
Stamp's EEPROM. You can also review these calibration values by running the program
and typing R instead of C. This will show a comparison of the actual vs. ideal angle
measurements in binary radians. These errors are caused in part by the printed circuit
board that the sensor is mounted on. Some of the materials in the printed circuit board
are magnetic, and are not necessarily aligned with the Earth's magnetic field. Other
magnetic field sources that can cause measurement errors come from nearby electrical
currents, such as electrons flowing through the Vdd and Vss lines to power your board's
power LED.
LOOP UNTIL status = Ready
SHIFTIN
HIGH En
IF (y.BIT10 = 1) THEN y = y | NegMask
IF (x.BIT10 = 1) THEN x = x | NegMask
RETURN
READ CompassOffsets, Word axisOffset
x = x - axisOffset
READ CompassOffsets + 2, Word axisOffset
y = y - axisOffset
RETURN
√
√
√
√
SHIFTIN
Run CalibrateCompass.bs2 again.
Click the Debug Terminal's Transmit windowpane and press Enter.
Type R to review the calibration settings.
Examine the errors reported, which the example program in the next activity will
use to make corrections.
DinDout,clk,MSBPOST,[x\11,y\11]
DinDout,clk,MSBPOST,[Status\4]
This subroutine relies on values stored in
Chapter 4: Hitachi HM55B Compass Module · Page 137
' Get Status
' Exit loop when status is ready
' Get x & y axis values
' Disable module
' Store 11-bits as signed word
' Repeat for other axis
' Get x-axis offset
' Correct x-axis
' Get y-axis offset
' Correct y-axis