Submitted by:
Ranjit Diol
This application note gives an example of using a TICkit 57 programmed with FBasic to run an electronic compass. All files for this note can be downloaded as a ZIP file, AN002.ZIP
The Vector Electronic Compass can be purchased from Jameco Electronics. The program uses some of FBasic's more interesting commands, like ALIAS. Mostly, however, the code is straight forward. An additional text file is included in the ZIP which provides more information.
The Program to control this circuit is below:
;VECTOR 2X in FBasic for the TICkit 20mhz code ; ;LCD interface for the VECTOR 2X (TM) from Precision Navigation, Inc ;which is available from Jameco Electronics. The device is a small high-tech, ;relatively low-cost (under $50) unit which sends out data based on ;magnetic directions - i.e.: An Electronic Compass which is very precise. ;This application for demonstration purposes assumes that ;an LCD (4-bit bus) has been attached to the TICkit. ; ;Modified VECTOR.BAS for the STAMP I (TM) from Scott Edwards Electronics. ;As published in Nuts & Volts magazine Dec 1996, Vol. 16 No:12 Page 117 ; ;by: ;======================================= ; COMPSys ; Ranjit Diol 6/30/96 ; rsdiol@bbs.lowe.org ; http://www.netservers.com/~rsdiol/ ;======================================= ; ;With special thanks to Glen Clark, Protean Logic Inc. for technical assistance. ;http://www.protean-logic.com
;and also to
;
;Mike Bergen, BMT,Inc. for affiliated support
;http://www.netservers.com/~bergenm/
;
;
DEF tickit_2
LIB fbasic.lib
GLOBAL byte xbuss_mask 0y00100001b ; These are required to address LCD
GLOBAL byte lcd_data_reg 0y00100001b ; in the lcd_send and lcd_init .libs
GLOBAL byte lcd_cont_reg 0y00100000b ; MUST precede following LIB lines.
LIB lcd.lib
;*** DEFINE CONSTANTS & VARIABLES ***
DEF SClk pin_D0 ; Pin 0 Clock Out to V2X SCLK Pin1
DEF DATAn pin_D1 ; Pin 1 Data In From V2X SDO Pin 2
DEF SSn pin_D2 ; Pin 2 Slave Select to V2X SS Pin 4
DEF PCn pin_D3 ; Pin 3 Poll/Cont Out to V2X P/C Pin 5
DEF EOCn pin_A0 ; Pin 8 EOC input from V2X EOC Pin 13
GLOBAL word hdg ;16bit variable for the heading
ALIAS byte hdgL hdg 0 ; LSB of hdg
ALIAS byte hdgH hdg 1 ; MSB of hdg
;***** INITIALIZATION **************
FUNCTION none main
LOCAL byte count 0b ; bit counter variable
BEGIN
;********** MAIN LOOP **************
REP
delay(500) ;1/2 second pause
pin_low(PCn) ;make pin output
pulse_out_high(PCn,1500) ;12ms pulse ( 1200 * 10us = 12ms )
=(hdg,0)
WHILE ==(pin_in(EOCn),0b) ;wait for end-of-conversion bit
;Wait for calc ready signal
LOOP
pin_low(SSn) ;Get ready to fetch word
delay(100) ;Wait awhile
=(count,0b) ;reset bit counter
REPEAT
=(hdgH,<<(hdgH)) ;shift data left 1 bit LSB first
pin_low(SClk) ;set clock to low
=(hdgH, or(hdgH, and(pin_in(DATAn),1b))) ;mask it with the bit received
pin_high(SClk) ;set clock back to high
++(count)
UNTIL ==( count,8b ) ;do it 8 times
=(count,0b) ;reset bit counter
REPEAT
=(hdgL,<<(hdgL)) ;shift data left 1 bit LSB first
pin_low(SClk) ;set clock to low
=(hdgL, or(hdgL, and(pin_in(DATAn),1b))) ;mask it with the bit received
pin_high(SClk) ;set clock back to high
++(count)
UNTIL ==( count,8b ) ;do it 8 times
pin_high(SSn) ;all done
;********** SEND OUTPUT TO LCD DISPLAY **********;
; NOTE: This portion can be modified. ;
; To conserve on pins it could be sent to ;
; a serial LCD interface or to any other device, ;
; gadget etc.
;************************************************;
IF <=(hdg,360) ;bypass errant readings
;of displaying trash
lcd_init() ;this redundant "inside-a-loop"
;(a waste of good mpu cycles!)
lcd_string("Heading: ") ;LCD initialization can coded
;before the main loop, however you
;will have to use a 'print_at' LCD
;function to prevent scrolling.
lcd_write_num(hdg) ;else display the heading
ENDIF
LOOP ;Start all over!
ENDFUN
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