Option explicit
Option default none
Option VCC 3.308
const r_trigger=2.3 'level to trigger trace and count BPM
const MAINSFREQ = 50
Const SAMPLESPERSEC = 4000
const MAXPULSE=500
Const AveragingFREQ = SAMPLESPERSEC/MAINSFREQ '20mSec to filter mains noise
CONST RTIME=60/MAXPULSE*AveragingFREQ 'minimum number of samples before we expect a new QRS complex
Const NSAMPLES = 48000
Dim integer i, j, k, BPMstate, BPMcount
Dim float a(NSAMPLES-1), displ(NSAMPLES / AveragingFREQ-1)
dim integer RPOS(100)
CLS

'
' convert the signals
'
ADC open SAMPLESPERSEC, 49,,, adc_done
ADC TRIGGER 1, r_trigger
do
ADC start a()
j=0
Do
Loop While j=0
k=0
BPMstate=RTIME 'don't look for an new QRS complex for RTIME samples
BPMcount=0
for i=0 to NSAMPLES / AveragingFREQ-1
displ(i)=0
for j=0 to AveragingFREQ-1
displ(i)=displ(i)+a(k)
k=k+1
next j
displ(i)=displ(i)/AveragingFREQ
' now evaluate BPM
' we know we were triggered by a QRS complex
if BPMstate > 0 then BPMstate = BPMstate - 1
if BPMstate = 0 and displ(i)>r_trigger then
RPOS(BPMcount)=i
BPMcount=BPMcount+1
RPOS(BPMcount)=i
BPMstate=RTIME
endif
next i

Box 99,0,603,MM.VRes,1,rgb(white),rgb(black)
For i=2 To 599
Line i+100, 250 - displ((i-2)\2)*75, i+102, 250 - displ(i\2)*75,, RGB(magenta)
cdisp(i\2-1)=displ(i\2-1)
Next i
line 100,250-r_trigger*75,699,250-r_trigger*75,,rgb(blue)
For i=600 To 1199
Line i-500, 470 - displ((i-2)\2)*75, i-498, 470 - displ(i\2)*75,, RGB(magenta)
Next i
line 100,470-r_trigger*75,699,470-r_trigger*75,,rgb(blue)
if BPMcount then text mm.hres\2,450,str$(60/(RPOS(BPMcount)/MAINSFREQ)*BPMcount,3,0)+" BPM",C,4
loop
'
End

Sub adc_done
j=1
End Sub