Serial Comms and Crystals

[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

[richard]

if you don't have a oscilloscope or logic analyser add some more diagnostics to the program

 ; 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 badresponce 'no response then give up
 while (!dht_data)
 wend 
 t2con=6
 while ( dht_data) 
 wend 
 t2con=0
 if ((tmr2 <45)||(tmr2>55))then goto badpresence ' 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,"tmr2 ",#tmr2
 
 next
 return
 badcrc:
 for bits=4 to 0 step-1 
 LCDOut $FE,$94 +16,hex dht[bits],"," 
pause 5000
 next 
 return
badresponse:
 LCDOut $FE,$94 +8,"nr "
 return

badpresence:
 LCDOut $FE,$94 +8,"pr",#tmr2
 return

[Scampy]

you did not make the changes I suggested

I changed the values for badread and noise as suggested, but still have the same result.

Sorry Richard, I must of confused you by posting the code with the values in the original code.

I'll take a look at your suggested code tomorrow and let you know - cheers for your help

EDIT - loaded the code as is and the LCD displays rh 0.0 nr
I assume that it's not getting a response from the sensor ? I have checked the connections and they appear correct (+ve to 5v, GND to ground, and signal to PORT A pin 1) this is connected via a header to the EasyPIC5 board with the 10K pull up resistors enabled (also tried without) I have a Hantek PC scope which I can use to test. I'm guessing I should see pin A1 going from high to low for the initial handshake between PIC and sensor ??

[richard]

expected dht response to start signal

[Scampy]

OK seems to of been a hardware issue. Replaced the sensor and now get a value on the lcd. The program is giving a reading of 870.4 - how would I turn this into a percentage

[Tabsoft]

Just to get a sense of the raw data collected, perhaps you can change your "main" subroutine to the follow and post the results output on the LCD?

main:
 gosub read_dht
 'LCDOut $FE,$94,"rh ",#hum/10,".",dec1 hum//10
 lcdout $FE, $94, hex2 dht(0), " ", hex2 dht(1), " ",hex2 dht(2), " ", hex2 dht(3), " ", hex2 dht(4)
 pause 4000
 goto main

[Scampy]

LCDOut $FE,$94,"rh ",#hum/10,".",dec1 hum//10 this gives a value of 870.4

lcdout $FE, $94, hex2 dht(0), " ", hex2 dht(1), " ",hex2 dht(2), " ", hex2 dht(3), " ", hex2 dht(4) produces 38 00 16 00 22

[Scampy]

In one of the other examples I've tested it has the following statement

humid=dht[31]*128+dht[30]*64+dht[29]*32+dht[28]*16+dht[27]*8+dht[26]*4+dht[25]*2+dht[24]*1

Using
lcdout $FE,$C0,"Humidity = ",#humid,"% " gives the humidity as a percentage.

Just trying to apply this to Richards code to get the same result

[Tabsoft]

Not using the DHT11 sensor, what is the temperature around your test rig?