Serial Comms and Crystals

[richard]

dht11/dht22
http://www.picbasic.co.uk/forum/showthread.php?t=19800

[Charlie]

You could use an HIH 4030. It outputs a voltage that you read with the ADC - as fast as you like.

[Scampy]

dht11/dht22
http://www.picbasic.co.uk/forum/showthread.php?t=19800

Thanks for the link. It states that it was for a 64mhz clock speed. Any idea what I need to change to make it run at 40 mhz ?

[richard]

this should be close

if ((tmr6 <75)||(tmr6>85))then goto badread

would become

if ((tmr6 <45)||(tmr6>55))then goto badread

and

if ((tmr6>20)&&(tmr6<80)) then     ' noise ?
           if (tmr6 >50 ) then

would become

 if ((tmr6>12)&&(tmr6<50 then     ' noise ?
           if (tmr6 >31 ) then

[Scampy]

Richard, thanks for the suggestions.

I'm in the process of editing the code (to reflect the pins I'm using and that I don't have a serial LCD), and came up with an error, presumably as I'm using 2.60 version rather than PBP 3 related to tmr6 and t6con statements. Any ideas

[richard]

pic 18F4580 has no timer6 try using tmr2 or rework the timer counts for timer3 with a 8:1 prescale

[Scampy]

Richard,

need some additional help. The following code compiled, but displayed RH 0.0 and tmr 0 on the LCD. I changed the values for badread and noise as suggested, but still have the same result. As mentioned I'm using a 10 mhz crystal with HS_ppl enabled to run the pic at 40 Mhz. Could you point me in the right direction as to what I'm doing wrong ?

; config settings 18F4580, 10mhz crystal HSPPL

ASM  
  __CONFIG    _CONFIG1H, _OSC_HSPLL_1H
  __CONFIG    _CONFIG2L, _PWRT_ON_2L  
  __CONFIG    _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
  __CONFIG    _CONFIG3H, _PBADEN_OFF_3H
  __CONFIG    _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
ENDASM

DEFINE  OSC 40
ADCON1 = $0F
clear
INCLUDE "alldigital.pbp"
CMCON = 7 
TRISA = %11001111

DEFINE LCD_DREG  PORTB           ' LCD Data port
DEFINE LCD_DBIT  0               ' starting Data bit (0 or 4)
DEFINE LCD_EREG  PORTB           ' LCD Enable port
DEFINE LCD_EBIT  5               '     Enable bit  (on EasyPIC 5 LCD)
DEFINE LCD_RSREG PORTB           ' LCD Register Select port
DEFINE LCD_RSBIT 4               '     Register Select bit   (on EasyPIC 5 LCD)
DEFINE LCD_BITS  4               ' LCD bus size (4 or 8 bits)
DEFINE LCD_LINES 4               ' number of lines on LCD
DEFINE LCD_COMMANDUS 2000        ' Command delay time in us 
DEFINE LCD_DATAUS 50             ' Data delay time in us 

ASM       
hum          = _dht+3    
tempa         = _dht+1
ENDASM 

T1CON = %00000001                               ; free-running, 1:1 prescaler

dht_data var PORTA.1
dht_dir var TRISA.1
dht var byte[5]

tempa var word EXT
bits var byte
crc   var byte
hum  var word EXT 

main:
gosub read_dht
LCDOut $FE,$94,"rh ",#hum/10,".",dec1 hum//10
pause 4000
goto main
    
read_dht:
     for bits=4 to 0 step-1 
       dht[bits]=0 
     next
    
     tmr2=0
     dht_dir=0
     dht_data=0
     pauseus 1000                   'start it up
     dht_data=1
     pauseus 30
     dht_dir=1
     pauseus 40                    'wait till middle of response pulse window
     if ( dht_data)then goto badread   'no response then  give up
     while (!dht_data)
     wend 
     t2con=6
     while ( dht_data) 
     wend 
     t2con=0
     if ((tmr2 <75)||(tmr2>85))then goto badread      ' confirm presence ?
     for  bits =39 to 0  step -1
         tmr2=0
         while (!dht_data) 
         wend 
         t2con=6
         while ( dht_data) 
         wend 
         t2con=0
         if ((tmr2>20)&&(tmr2<80)) then     ' noise ?
           if (tmr2 >50 ) then
              dht.0[bits] =  1 
           endif   
           
         else
          goto badread          ' noise ?
         endif
     next 
     crc=0 
     for bits=1 to 4         
       crc=crc+ dht[bits]
       
     next
     if crc !=  dht[0] then goto badcrc    'crc

return
  
badread:
LCDOut $FE,$94 +8,"tmr6 ",#tmr2
    for bits=4 to 0 step-1 
       dht[bits]=0 
    next
return
badcrc:
    for bits=4 to 0 step-1 
LCDOut $FE,$94 +16,hex dht[bits],"," 
    next  
return

[richard]

you did not make the changes I suggested

; config settings 18F4580, 10mhz crystal HSPPL

ASM
__CONFIG _CONFIG1H, _OSC_HSPLL_1H
__CONFIG _CONFIG2L, _PWRT_ON_2L
__CONFIG _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
__CONFIG _CONFIG3H, _PBADEN_OFF_3H
__CONFIG _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
ENDASM

DEFINE OSC 40
ADCON1 = $0F
clear
INCLUDE "alldigital.pbp"
CMCON = 7
TRISA = %11001111

DEFINE LCD_DREG PORTB ' LCD Data port
DEFINE LCD_DBIT 0 ' starting Data bit (0 or 4)
DEFINE LCD_EREG PORTB ' LCD Enable port
DEFINE LCD_EBIT 5 ' Enable bit (on EasyPIC 5 LCD)
DEFINE LCD_RSREG PORTB ' LCD Register Select port
DEFINE LCD_RSBIT 4 ' Register Select bit (on EasyPIC 5 LCD)
DEFINE LCD_BITS 4 ' LCD bus size (4 or 8 bits)
DEFINE LCD_LINES 4 ' number of lines on LCD
DEFINE LCD_COMMANDUS 2000 ' Command delay time in us
DEFINE LCD_DATAUS 50 ' Data delay time in us

ASM
hum = _dht+3
tempa = _dht+1
ENDASM

T1CON = %00000001 ; free-running, 1:1 prescaler

dht_data var PORTA.1
dht_dir var TRISA.1
dht var byte[5]

tempa var word EXT
bits var byte
crc var byte
hum var word EXT

main:
gosub read_dht
LCDOut $FE,$94,"rh ",#hum/10,".",dec1 hum//10
pause 4000
goto main

read_dht:
for bits=4 to 0 step-1
dht[bits]=0
next

tmr2=0
dht_dir=0
dht_data=0
pauseus 1000 'start it up
dht_data=1
pauseus 30
dht_dir=1
pauseus 40 'wait till middle of response pulse window
if ( dht_data)then goto badread 'no response then give up
while (!dht_data)
wend
t2con=6
while ( dht_data)
wend
t2con=0
if ((tmr2 <45)||(tmr2>55))then goto badread ' confirm presence ?
for bits =39 to 0 step -1
tmr2=0
while (!dht_data)
wend
t2con=6
while ( dht_data)
wend
t2con=0
if ((tmr2>12)&&(tmr2<50)) then ' noise ?
if (tmr2 >31 ) then
dht.0[bits] = 1
endif

else
goto badread ' noise ?
endif
next
crc=0
for bits=1 to 4
crc=crc+ dht[bits]

next
if crc != dht[0] then goto badcrc 'crc

return

badread:
LCDOut $FE,$94 +8,"tmr6 ",#tmr2
for bits=4 to 0 step-1
dht[bits]=0
next
return
badcrc:
for bits=4 to 0 step-1
LCDOut $FE,$94 +16,hex dht[bits],","
next
return