DS1820 and 18f2550

[Acetronics2]

Ok,

Reading closer the datasheet shows there are time slots for writing and reading ...

so, rub out your PAUSE 2000 ...

but keep on polling DQ !

Alain

[rjones2102]

Thanks again mate but your code, the code I tried last, didn't have a pause 2000. That was mine. Your code never gets past the wait loop either. Here is code again for clarity. I appreciate it isn't going to work later in code as I haven't done anything with offset etc but there is no point till I get past the wait loop for ds1820 to become ready.

define OSC 48
ADCON1 = 7            ' Set PORTA to digital
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 225 ' 9600 Baud @ 48MHz, 0.0%
SPBRGH = 4
BAUDCON.3 = 1         ' Enable 16 bit baudrate generator
HSEROUT [13,10,"Starting"]

DQ var PORTA.0
temperature var word
count_remain var word
count_per_c var word
offset var word
'************************************************* ****************************
' Start temperature conversion
'************************************************* ****************************

mainloop: OWOut DQ, 1, [$CC, $44 ]

'************************************************* ****************************
' Check for still busy converting ( ~ 4500 times ... )
'************************************************* ****************************

waitloop:

INPUT DQ
If NOT DQ Then waitloop

high PORTA.5 ' turn on LED if it gets past this point

'************************************************* ****************************
' Read the temperature
'************************************************* ****************************

OWOut DQ, 1, [$CC, $BE ]

OWIn DQ, 0, [temperature.LOWBYTE, temperature.HIGHBYTE, Skip 4, count_remain, count_per_c]

'************************************************* ****************************
' Calculate temperature in degrees C to 2 decimal places (not valid for negative temperature)
'************************************************* ****************************

temperature = (((temperature >> 1) * 100) - 25) + (((count_per_c - count_remain) * 100) / count_per_c)+ offset

Lcdout $fe, 1, DEC (temperature / 100), ".", DEC2 temperature, " ",$DF,"C"

'************************************************* ****************************
' Calculate temperature in degrees F to 2 decimal places (not valid for negative temperature)
'************************************************* ****************************

temperature = (temperature */ 461) + 3200
'Lcdout $fe, $c0, DEC (temperature / 100), ".", DEC2 temperature, " ",$DF,"F"
HSEROUT [13,10, " Temp = ",DEC (temperature / 100), ".", DEC2 temperature, " ","F"]
goto mainloop

[Bruce]

Try ADCON1 = 15 VS ADCON1 = 7. You are leaving most of PORTA setup as analog inputs.

[Acetronics2]

Did you disable Porta Comparators ??? looks no ...

Default setting ... ok, but ...

EXAMPLE 10-1: INITIALIZING PORTA

CLRF PORTA ; Initialize PORTA by
; clearing output
; data latches
CLRF LATA ; Alternate method
; to clear output
; data latches
MOVLW 0Fh ; Configure A/D
MOVWF ADCON1 ; for digital inputs
MOVLW 07h ; Configure comparators
MOVWF CMCON ; for digital input
MOVLW 0CFh ; Value used to
; initialize data
; direction
MOVWF TRISA ; Set RA<3:0> as inputs
; RA<5:4> as outputs

Even Microchip does it !!! ...

Alain

[rjones2102]

Bruce/Alain THANKYOU SO MUCH!!

The ADCON1=15 did it and I also tried your ASM example Alain. They both fixed it. Sorry, I am new to this (well, 2 weeks new) and keep thinking I have the hang of it then learning more! I thought ADCON1=7 had disabled analogue inputs on all pins. I'll read that bit of DS before I go to bed so I have actually learnt it rather than having been spoon fed! Thanks!! OK, read it and learnt something very important. The DS is the bible, if only I could understand it!

Just read example 10.1. For the first time ever the example makes some sense to me and I can see why it is relevant to us PBPers. Wow!

I was just about to go to bed miserable. I got USB going today, wanted to feed temperature to VB instead of just my name. So much is coming together! 24LC256 challenge tomorrow!

Now I can wake up to a new day and a new phase of project!

THANKS SO MUCH
Rich