read_lm335:
FOR n = 1 TO 4			'read 4 of 8 A/D channels with LM335 sensors attached
    OUT bbase_ad+2,n-1	        'starting with channel 0, MUX write control byte
    DELAY 0.05			'small delay needed between writes to converter
    OUT bbase_ad+1,0	        'any write to this address causes A/D conversion
    scount=0

    label_3:
    statusreg=INP(bbase_ad+2)	'check to see if A/D conversion is done
    eoc=BIT(statusreg,7)		'check bit 7 for end of conversion
    INCR scount
    IF scount=10 GOTO label_5	'prevent hanging if no A/D card
    IF eoc=1 THEN GOTO label_3	'if eoc=1 A/D is busy, if 0 is done

   	lsb=INP(bbase_ad)       		'read lower byte value
	msb=INP(bbase_ad+1)			'read upper byte value
	bitpattern$=BIN$(lsb)			'give it an alpha pattern
	bitpattern2$=BIN$(msb)
	ad_channel=statusreg AND &b111	'read lower 3 bits to identify A/D channel
   	msb=msb*16					'shift msb to left 0000 bits
	SHIFT RIGHT lsb, 4				'read left nibble of bbase+1
	ad_counts=msb+lsb				'add bytes to get word

    SELECT CASE ad_channel			'calibrations using 5v regulated supply
    CASE=0
        degf(r,n)=(ad_counts-3087.96)/2.2512		'hp-48 cal for #1 in breezeway
    CASE=1
        degf(r,n)=(ad_counts-3085.326)/2.268		'hp-48 cal for #2 in 2nd floor
    CASE=2
        degf(r,n)=(ad_counts-3090.873)/2.3036		'hp-48 cal for #3 in 1st floor
    CASE=3
        degf(r,n)=(ad_counts-3093.087)/2.2666		'hp-48 cal for #4 in basement
    CASE ELSE
        degf(r,n)=(ad_counts-3088.713)/2.2979		'use spare #5 if more channels
    END SELECT

	IF debug_flag=1 THEN
		PRINT #6, ad_channel, bitpattern2$, bitpattern$, ad_counts, degf(r,n)
		WRITE #7, TIME$,r,degf(r,1),degf(r,2),degf(r,3),degf(r,4)  'write to ad_degs.log
    END IF
	IF auto_test_flag=1 THEN GOSUB show_all_deg		'display house temperatures
NEXT n
    INCR r							'the sample count
IF debug_flag=1 THEN
	PRINT #6, ""
	WRITE #7,
END IF

IF r=4 THEN					'after 4 readings, average the data
	deg_F1=(degf(0,1)+degf(1,1)+degf(2,1)+degf(3,1))/4
	deg_F2=(degf(0,2)+degf(1,2)+degf(2,2)+degf(3,2))/4
	deg_F3=(degf(0,3)+degf(1,3)+degf(2,3)+degf(3,3))/4
	deg_F4=(degf(0,4)+degf(1,4)+degf(2,4)+degf(3,4))/4
	GOSUB save_temp			         'record the average values
   	r=0
END IF

label_5:
RETURN