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' h48c_3-axis_wpd_enabled.bs2
'
' THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
' ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
' THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
' PARTICULAR PURPOSE.
'
' Copyright (c) Microsoft Corporation. All rights reserved
'
' {$STAMP BS2}
' {$PBASIC 2.5}
'
' =========================================================================
' -----[ Program Description ]---------------------------------------------
'
' Test program for the H48C 3-Axis Accelerometer module.
'
' Connections:
'
' +------------+
' | * |
' CLK | o o | Vdd (+5v)
' | +--+ |
' DIO [ o | | o | CS\
' | +--+ |
' Vss | o o | 0G (free-fall indication)
' | |
' +------------+
'
' How it Works:
'
' An onboard MCP3204 12-bit ADC is used to read the VRef, X-, Y-, and
' Z-axis outputs from the Hitachi H48C accelerometer. The reference
' voltage output from H48C is 1.65 volts (3.3 / 2).
'
' After reading the reference voltage and an output channel the g-force
' for the channel is calculated with this formula:
'
' axis - vref 3.3
' G = ----------- x ------
' 4095 0.3663
'
' For use in the program the forumla can be simplified to:
'
' G = (axis - vref) x 0.0022
'
' To allow the display of fractional g-force in the integer system of the
' BASIC Stamp we multiply 0.0022 by 100 -- this will allow us to display
' g-force in 0.01g units.
' -----[ I/O Definitions ]-------------------------------------------------
Dio PIN 15 ' data to/from module
Clk PIN 14 ' clock output
CS PIN 13 ' active-low chip select
' -----[ Constants ]-------------------------------------------------------
XAxis CON 0 ' adc channels
YAxis CON 1
ZAxis CON 2
VRef CON 3
Cnt2Mv CON $CE4C ' counts to millivolts
' 0.80586 with **
GfCnv CON $3852 ' g-force conversion
' 0.22 with **
' -----[ Variables ]-------------------------------------------------------
axis VAR Nib ' axis selection
rvCount VAR Word ' ref voltage adc counts
axCount VAR Word ' axis voltage adc counts
mVolts VAR Word ' millivolts
Gforce VAR Word ' axis g-force
xGforce VAR Word ' x-axis force
yGforce VAR Word ' y-axis force
zGforce VAR Word ' z-axis force
dValue VAR Word ' display value
dPad VAR Nib ' display pad
' Below lines are WPD additions
SensorID VAR Byte 'Sensor identifier = 9 for Hitachi
ElementCount VAR Byte 'Count of elements in packet
ElementSize VAR Byte 'Size (in bytes) of each element
NewInterval VAR Word 'New interval requested by user
Interval VAR Word 'Interval value utlized by firmware
SensorID = 9
ElementSize = 4 'Each element contains a sign byte, followed by a G-force integer value, followed by a G-force fraction (in hundredths).
ElementCount = 3 'Each element corresponds to one of the three axis (X, Y, and Z)
Interval = 2000
NewInterval = 2000
' -----[ EEPROM Data ]-----------------------------------------------------
' -----[ Initialization ]--------------------------------------------------
Reset:
HIGH CS ' deselect module
' -----[ Program Code ]----------------------------------------------------
Main:
GOSUB GetGforces 'Retrieves G-forces along 3 axis
GOSUB RetrieveInterval 'Retrieves event-interval data
Timeout:
SEROUT 16, 16780, [DEC1 SensorID, DEC1 ElementSize, DEC1 ElementCount, DEC1(xGforce.BIT15), DEC1(ABS xGforce/100),DEC2(ABS xGforce),DEC1(yGforce.BIT15),DEC1(ABS yGforce/100),DEC2(ABS yGforce),DEC1(zGforce.BIT15),DEC1(ABS zGforce/100),DEC2(ABS zGforce),DEC5 Interval ]
GOTO Main
GOTO Main
' -----[ Subroutines ]-----------------------------------------------------
' Retrieves the event-interval property from the WPD driver
RetrieveInterval:
SERIN 16, 16780, Interval, Timeout, [DEC NewInterval] 'Retrieve interval
IF NewInterval >= 10 AND NewInterval <= 60000 THEN
Interval = NewInterval
ENDIF
' Retrieves G forces along all three axis
GetGforces:
FOR axis = XAxis TO ZAxis ' loop through each axis
GOSUB Get_H48C ' read vRef & axis counts
' calculate g-force
' -- "Gforce" is signed word
IF (axCount >= rvCount) THEN
Gforce = (axCount - rvCount) ** GfCnv ' positive g-force
ELSE
Gforce = -((rvCount - axCount) ** GfCnv) ' negative g-force
ENDIF
IF (axis = XAxis) THEN
xGforce = Gforce
ENDIF
IF (axis = YAxis) THEN
yGforce = Gforce
ENDIF
IF (axis = ZAxis) THEN
zGforce = Gforce
ENDIF
NEXT
RETURN
' Reads VRef and selected H48C axis through an MCP3204 ADC
' -- pass axis (0 - 2) in "axis"
' -- returns reference voltage counts in "rvCount"
' -- returns axis voltage counts in "axCounts"
Get_H48C:
LOW CS
SHIFTOUT Dio, Clk, MSBFIRST, [%11\2, VRef\3] ' select vref register
SHIFTIN Dio, Clk, MSBPOST, [rvCount\13] ' read ref voltage counts
HIGH CS
PAUSE 1
LOW CS
SHIFTOUT Dio, Clk, MSBFIRST, [%11\2, axis\3] ' select axis
SHIFTIN Dio, Clk, MSBPOST, [axCount\13] ' read axis voltage counts
HIGH CS
RETURN
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