DS1820 and 18f2550

There are so many threads/ articles on the net about this but I am still failing to get it working. If anyone has a good idea, please HELP ME!

I have the DS1820 wired with 5 volts on pin 3, a 4.7 k pullup on pin 2 to PortA.0 on Pic and pin 1 to gnd. I have measured voltages with and without the 18f2550 in place to verify the voltage on pin 3 of DS1820 is coming from pullup. I am 99.999% certain electrically it is all good.

My fuse are setup as follows as I have USB comms running but not for the duration of the DS1820 tests just to make it simple. I am using a 20Mhz OSC and USB comms works fine so I am confident about Osc config etc at least for USB. OW doesn't have any special requirements does it?.

Code:

__CONFIG _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L ; ; USB clock source comes from the 96 MHz PLL divided by 2 ; ; [OSC1/OSC2 Src: /1][96 MHz PLL Src: /2] ; No prescale (4 MHz oscillator input drives PLL directly) __CONFIG _CONFIG1H, _FOSC_HSPLL_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H ; ; ; Oscillator Switchover mode disabled ; ; Fail-Safe Clock Monitor disabled ; XT oscillator, PLL enabled, XT used by USB __CONFIG _CONFIG2L, _PWRT_ON_2L & _BOR_ON_2L & _BORV_2_2L & _VREGEN_ON_2L __CONFIG _CONFIG2H, _WDT_OFF_2H __CONFIG _CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H & _CCP2MX_ON_3H __CONFIG _CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L & _XINST_OFF_4L & _DEBUG_OFF_4L

I have tried 2 pieces of code. First one just outputs
Busy
Busy
Busy
.....

To Hyperterm:

Code:

DEFINE OSC 48 ' We're using a 20MHz oscillator ADCON1 = 7 ' Make pins 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"] Comm_Pin VAR PortA.0 ' One-wire Data-Pin "DQ" on PortC.0 Busy VAR BIT ' Busy Status-Bit R_Temp VAR WORD ' RAW Temperature readings TempC VAR WORD ' Temp in deg C TempF VAR WORD ' Temp in deg F Float VAR WORD ' Holds remainder for + temp C display Cold_Bit VAR R_Temp.Bit11' Sign-Bit for +/- Temp. 1 = Below 0 deg C Real_Cold CON 1 ' Define Real_Cold = 1 BAUD CON 16468 ' N9600 for serial LCD DISP VAR PortB.0 ' Pin to drive serial LCD Deg CON 223 ' Data to display Deg ° symbol CLR CON 1 ' CLR LCD command LINE1 CON 128 ' LCD line #1 LINE2 CON 192 ' LCD line #2 LINE3 CON 148 ' LCD line #3 LINE4 CON 212 ' LCD line #4 INS CON 254 ' LCD command mode parameter Sign VAR BYTE ' +/- sign for temp display Dummy VAR BYTE ' Dummy for Div32 Start_Convert: OWOUT Comm_Pin, 1, [$CC, $44]' Skip ROM search & do temp conversion Pause 2000 Wait_Up: OWIN Comm_Pin, 4, [Busy] ' Read busy-bit hserout [13,10,"Busy"] pause 100 IF Busy = 0 THEN Wait_Up ' Still busy..?, Wait_Up..! OWOUT Comm_Pin, 1, [$CC, $BE]' Skip ROM search & read scratchpad memory OWIN Comm_Pin, 2, [R_Temp.Lowbyte, R_Temp.Highbyte]' Read two bytes / end comms GOSUB Convert_Temp GOTO Start_Convert Convert_Temp: ' +32.0 to +257 F IF Cold_Bit = Real_Cold THEN Yikes ' If Cold_Bit = 1, it's below "0" deg C Sign = "+" Dummy = 625 * R_Temp ' Multiply to load internal registers with 32-bit value TempC = DIV32 10 ' Use Div32 value to calculate precise deg C Dummy = 1125 * R_Temp TempF = DIV32 100 IF TempF >6795 THEN ' Over 99.5 deg F..? TempF = TempF + 3200 HSEROUT [13,10, " TempF = ",Sign,DEC TempF DIG 4,_ DEC TempF DIG 3,DEC TempF DIG 2,".",DEC2 TempF,Deg,"F "] ELSE TempF = TempF + 3200 HSEROUT [13,10, " TempF = ",Sign,DEC TempF DIG 3,_ DEC TempF DIG 2,".",DEC2 TempF,Deg,"F "] ENDIF TempC = (R_Temp & $0FF0) >> 4 ' Mask middle 8-bits, shift into lower byte Float = ((R_Temp.Lowbyte & $0F) * 625) ' Lower 4-bits of result * 625 HSEROUT [13,10, " TempC = ",Sign,DEC TempC,".",DEC Float,Deg,"C "] HSEROUT [13,10, "Raw", IBIN16 R_Temp] RETURN Yikes: ' Display full range -C to -F conversion Sign = "-" ' Display - symbol for negative temp Dummy = 625 * ~R_Temp+1' Multiply to load internal registers with 32-bit value TempC = DIV32 10 ' Use Div32 value to calculate precise deg C TempF = ~R_Temp / 16 ' Begin conversion from -C to deg +/-F IF TempF >=18 THEN ' Check for -degrees F "-18 C = -0.4 F" TempF = ((((TempF + 50) * 9) /5) -122) ' -C to -F below -17 deg C HSEROUT [13,10, " TempF = ",Sign, DEC TempF,Deg,"F "] HSEROUT [13,10, " TempC = ",Sign,DEC TempC DIG 4,_ DEC TempC DIG 3,".",DEC3 TempC,Deg,"C "] HSEROUT [13,10, "Raw", IBIN16 R_Temp] ELSE ' Else result = +deg F TempF = ((((-TempF + 50) * 9) /5) -58)' -C to +F below 32.0 deg F to -17 deg C HSEROUT [13,10, " TempF = ","+",DEC TempF,Deg,"F "] HSEROUT [13,10, " TempC = ",Sign,DEC TempC DIG 4,_ DEC TempC DIG 3,".",DEC3 TempC,Deg,"C "] HSEROUT [13,10, "Raw", IBIN16 R_Temp] ENDIF RETURN END

The second really simple bit of code just outputs 00.0

Code:

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 temp var word loop: owout DQ,1,[$cc] owout DQ,0,[$44] Pause 2000 owout DQ,1,[$cc] owout DQ,0,[$be] owin DQ,0,[temp.byte0,temp.byte1] temp=temp*5 HSEROUT [13,10, " Temp = ",DEC2 temp/10,".", dec1 temp," ","C"] goto loop

These bits of code come from sources that swear they work. What else could it be?!?!! For now I will try and send something else down USB to VB!!

Hope someone can help.

Thanks a lot

Rich

Hi, Rich

I have a DS1820 "on board" ... I look at that.

Here is an excerpt of my test program:

'************************************************* ****************************
' Start temperature conversion
'************************************************* ****************************

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

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

waitloop:

INPUT DQ
If NOT DQ Then waitloop

'************************************************* ****************************
' 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"

the major thing is see is here :

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

as you receive more than 16 bits ... and your "buffer" is only 16 bits.

The Scratchpad is always FULLY read ( 8 bytes ), so you must skip the last locations.

see datasheet on page 8 for scratchpad details.

Alain

Thanks for your help mate,

I tried using your code but my problem is earlier on than the number of bytes being read. I put this 'turn LED line on' line after the wait loop. The LED never comes on. My ds1820 is never being ready I guess. I have double checked wiring. I know it's an odd one. Any more ideas just to get me past the wait loop. Once I am past there I can work the rest out from your fabulous info!

If NOT DQ Then waitloop
high PORTA.5
' the LED never comes on (but of course it does if I put the line before the loop!)

Regards

Rich

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

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.

Code:

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

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

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

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