' DHT11 decoder using ADC
 ' TassyJim May 2021
 ' when using the ADC, the DHT** has to be run on 3.3V and use one of the ADC input pins
 ' The external 4.7k pullup to 3.3V is required.
 '
 DIM FLOAT te, hu
 DIM FLOAT a_in(500)
 DIM INTEGER alldone
 DIM INTEGER dht_pin = 15 '15 on the F4, ?? on the CMM2
 DO
   HUMID dht_pin,te,hu
   PAUSE 2000
   HUMID dht_pin,te,hu ' take two reading to remove stale reading from the mix
   PRINT te,hu
   PAUSE 2000
   dht11 dht_pin,te,hu
   PRINT te,hu
   PRINT
   PAUSE 15000
 LOOP
 
SUB dht11 pn, tem, hum
 LOCAL INTEGER n, count, running, x = 1
 LOCAL INTEGER repl(5)
 LOCAL reply$
 alldone = 0
 PIN(pn) = 1
 SETPIN pn, DOUT, OC
 PAUSE 2
 PIN(pn) = 0
 PAUSE 18 ' this is the start pulse length - 18 for the DHT11, 1 for DHT22
 PIN(pn) = 1
 SETPIN pn, OFF ' make way for the ADC to take over the pin
 ADC OPEN 100000,pn,,,adc_done ' sample every 10uS
 ADC START a_in()
 DO
 LOOP UNTIL alldone = 1
 FOR n = 0 TO 500
   IF running = 0 THEN
     IF a_in(n) < 1.6 THEN running = 1
   ENDIF
   IF running THEN
     IF a_in(n) > 1.6 THEN
       count = count + 1
     ELSE
       IF count > 0 THEN
         PRINT count;
         IF count > 5 THEN
           reply$= reply$+"1" ' we could use an integer instead of a string
         ELSE
           reply$ = reply$+"0"
         ENDIF
         count = 0
       ENDIF
     ENDIF
   ENDIF
 NEXT n
 PRINT
 FOR n = 0 TO 4
   repl(n) = VAL("&b"+MID$(reply$,n*8+x,8))
 NEXT n
 hum = (repl(0)*256+repl(1))/10
 tem = repl(2)*256+repl(3)
 IF tem > 32767 THEN tem = tem - 65536
 tem = tem/10
 PRINT reply$
 PRINT repl(0),repl(1),repl(2),repl(3),repl(4)," ch_sum ";(repl(0)+repl(1)+repl(2)+repl(3)) AND 255
END SUB
 
SUB adc_done
 alldone = 1
 ADC CLOSE
END SUB

18.9 53.4
3 3 2 2 2 2 7 2 2 2 2 7 3 8 3 7 3 3 3 3 3 3 3 3 8 3 7 7 8 8 3 7 7 8 3 7 2 7 3 3
0000001000010101000000001011110111010100
2 21 0 189 212 ch_sum  212
18.9 53.3

18.9 53.3
3 2 2 2 2 2 7 2 2 2 2 7 3 8 3 7 3 3 3 3 3 3 3 3 8 3 7 7 8 8 2 7 7 8 3 7 2 7 3 3
0000001000010101000000001011110111010100
2 21 0 189 212 ch_sum  212
18.9 53.3

18.9 53.4
2 2 2 2 2 2 7 3 2 2 2 7 3 8 7 2 3 3 3 3 3 3 3 2 8 2 7 7 8 7 2 7 8 8 3 7 2 7 3 8
0000001000010110000000001011110111010101
2 22 0 189 213 ch_sum  213
18.9 53.4

   // we have all 40 bits
   // first validate against the checksum
   if( ( ( ((r >> 8) & 0xff) + ((r >> 16) & 0xff) + ((r >> 24) & 0xff) + ((r >> 32) & 0xff) ) & 0xff) != (r & 0xff)) goto error_exit;                                           // returning temperature
   if(DHT22){
*temp = (MMFLOAT)((r >> 8) &0x7fff) / 10.0;                       // get the temperature
if((r >> 8) &0x8000) *temp = -*temp;                            // the top bit is the sign
*humid = (MMFLOAT)(r >> 24) / 10.0;                               // get the humidity
   } else {
*temp = (MMFLOAT)((signed char)((r>>16) & 0xFF));                       // get the temperature
*humid = (MMFLOAT)((signed char)(r >> 32));                               // get the humidity
   }