'  Title:  Digital dB Converter
'  File Name:  db60.bs2
'  Range:  60dB (3.0 decades)
'  Resolution:  255 counts/60 dB = 4.25 counts/dB
'  Hardware:  Basic Stamp II + op amp + A/D + analog mux
'  Four selectable op amp gains in 5.623:1 ratio
'  Author:  Allen Rushing, arushing@rochester.rr.com
'		429 Tara Lane 
'		Webster, NY 14580
'		Copyright(c) Allen Rushing (This work is unpublished.)
LUT00 data @0,0,0,1,2,3,3,4,5,6,6,7,8,8,9,10,10,11,11,12,13
LUT01 data @20,13,14,14,15,15,16,16,17,17,18,18,19,19,20,20,21,21,22,22,23
LUT02 data @40,23,23,24,24,25,25,26,26,26,27,27,27,28,28,29,29,29,30,30,30
LUT03 data @60,31,31,32,32,32,33,33,33,34,34,34,34,35,35,35,36,36,36,37,37
LUT04 data @80,37,38,38,38,38,39,39,39,40,40,40,40,41,41,41,41,42,42,42,42
LUT05 data @100,43,43,43,43,44,44,44,44,45,45,45,45,46,46,46,46,47,47,47,47
LUT06 data @120,47,48,48,48,48,49,49,49,49,49,50,50,50,50,50,51,51,51,51,52
LUT07 data @140,52,52,52,52,53,53,53,53,53,53,54,54,54,54,54,55,55,55,55,55
LUT08 data @160,56,56,56,56,56,56,57,57,57,57,57,57,58,58,58,58,58,58,59,59
LUT09 data @180,59,59,59,59,60,60,60,60,60,60,61,61,61,61,61,61,61,62,62,62
LUT10 data @200,62,62,62,63,63,63,63,63,63,63,64
db 	var 	byte	'0-255 scaled decibel conversion of the input
delt 	var 	byte	'the db increment according to gain
k	var 	word	'counter
ADC	var	inl	'A/D output byte, connected to BS2 P0(lsb) to P7(msb)
code	var	outh	'code (0-3) to select the op amp gain
dirl=%00000000	'low byte I/O pins (P0-7) receive A/D count as input
dirh=%00000111	'P8-9 for gain code output to DG408; P10 for PWM output
'code outputs gain code to switch: 0,1,2,3 for 
'nominal gains of 178, 31.6, 5.62, 1.00, respectively.
'Initialize gain code; start with smallest gain (code=3)
 code=3
' k=0
again:				'main loop
' pause 500			'slow down to view debug; remove pause for PWM
' if k=10000 then timeout
' k=k+1
 if ADC=255 then gmin_test	'A/D saturated?
 if ADC<45 then gmax_test	'A/D count too low?
 'read scaled dB from the LUT; then add delt according to gain
 read ADC-45, db
 lookup code,[0,64,128,192],delt	'lookup the increment
 db=db+delt			'db byte (0-255)
 pwm 10,db,5		'DAC by pulse-width-modulated pin 10; 5 cycles
debug ? code, ? ADC, ? db, CR	'show the gain code & scaled db
				'enabling this debug slows down the update rate
 goto again				'loop endlessly
gmin_test:			'is the gain minimum?
 if code=3 then range_hi	'input is too big
 code=code+1			'increment code to decrease gain
 goto again				'loop endlessly
gmax_test:			'is the gain maximum?
 if code=0 then range_lo	'input is too small
 code=code-1			'decrement code to increase gain
 goto again:			'loop endlessly
range_hi:			'error message:
 debug "input too big", CR	'input too big-saturated at min gain; db>255
 goto again				'loop endlessly
range_lo:			'error message:
 debug "input too small", CR	'input too small for the LUT; db < 0
 goto again				'loop endlessly
timeout:
 debug ? k				
 end