ds18s20 reads incorectly

[jcleaver]

i have attached the 2 programs one in pbp which reads temperature incorectly
the other mikroe which works no hardware changes are made really interested in the difference


thanks

jack

[skimask]

i have attached the 2 programs one in pbp which reads temperature incorectly
the other mikroe which works no hardware changes are made really interested in the difference


thanks

jack

Speaking strictly about PBP....
You know, just like it says in the manual, define's have to be in CAPS.
Therefore, the
define osc 20
is ignored and the timing generated by the code is generated for an oscillator of 4mhz, but apparently you are running it at 20mhz, and therefore, probably far too fast.
Did you write this code or copy/paste it? Why not use PBP's built-in OWIN/OWOUT commands?

[manwolf]

maybe you should check the math.
With a change to the math the program works correctly. Running on a EasyPIC5 board.

Sorry I was sleeping that day in class, so I can't explain why PBP and MBasic work differently.

[Acetronics2]

Why not use PBP's built-in OWIN/OWOUT commands?

The solution simply is here ...

MKB reads Byte by Byte and Pbp ... as you want !

just need to program a correct reading with Pbp !



Further ... TempF = TempC *9/5 + 32 ...

Remember PbP works with UNSIGNED INTEGERS ...

Alain

PS: Ski, MKB has a built-in timing adjustment,( you check an option in the project window instead of writing a DEFINE ) and The "conversion complete" polling built-in. That surprised me a bit at first time, not to see it in the source listing ...

[jcleaver]

the osc is correct dont know why it did not show caps
tried going with 4 still read low
? what changes in math
TEMP = ((TEMP*9/5)+32 ) is what i am using
thanks for the inputs

have not found any samples using owin with this chip

[Acetronics2]

Hi,

Did you ever try SEARCH with the 1820 Keyword ???

Surely NO !!!

I remember having posted a while ago for the DS1820 ...

Gives ... 22 Hits !

Alain

[skimask]

I remember having posted a while ago for the DS1820 ...
Gives ... 22 Hits !
Alain

23 Hits now!
But, he's also using the DS18S20.
I know...I know...not a lot of difference between the two that can't be handled by a simple read of the datasheet.

[skimask]

the osc is correct dont know why it did not show caps
tried going with 4 still read low
? what changes in math
TEMP = ((TEMP*9/5)+32 ) is what i am using
thanks for the inputs

have not found any samples using owin with this chip

Ok, try this:

@ DEVICE pic16F877A, HS_OSC
@ DEVICE pic16F877A, WDT_ON
@ DEVICE pic16F877A, PWRT_ON
@ DEVICE pic16F877A, BOD_ON
@ DEVICE pic16F877A, MCLR_on
@ DEVICE pic16F877A, LVP_OFF
@ DEVICE pic16F877A, CPD_OFF
@ DEVICE pic16F877A, PROTECT_OFF
define osc 20
define loader_used 1
define lcd_dreg portd
define lcd_dbit 4
define lcd_rsreg portd
define lcd_rsbit 2
define lcd_ereg portd
define lcd_ebit 3
define lcd_lines 2
define lcd_bits 4
define lcd_commandus 2000
define lcd_dataus 50
command var byte:i var byte:temp var word:dq var porta.5:dq_dir var trisa.5
adcon1=255:porta=255:portb=0:trisa=255:trisb=0:cmcon=7
Lcdout $fe,1,"Temp in degrees C"
mainloop:	Gosub init1820:command=$cc:Gosub write1820:command=$44
Gosub write1820:Pause 2000:Gosub init1820:command=$cc:Gosub write1820
Pause 2000:command=$be:Gosub write1820:Gosub read1820:TEMP=((TEMP*9/5)+32)
Lcdout $fe,1,dec(temp>>1),".",dec(temp.0*5)," degrees C":Goto mainloop
init1820:	Low DQ:Pauseus 500:DQ_DIR=1:Pauseus 100
If DQ=1 Then Lcdout $fe,1,"DS1820 not present":Pause 500:Goto mainloop
Pauseus 400:Return
write1820:	For i=0 to 7:low dq
If command.0[temp] = 0 Then
	Pauseus 60:DQ_DIR = 1
Else
	@ nop
	DQ_DIR = 1:Pauseus 60
Endif
Next i:Return
read1820:	For i=0 to 15:low dq
		@ nop
		dq_dir=1:temp.0[i]=1:if dq=0 then temp.0[i]=0
		pauseus60:next i:return
End

[jcleaver]

Tried This And Get Better Reading Only 6 Deg Low

However It Does Not Respond To Any Temperature Changes

Thanks