TheBackShed.com

Forum Index : Microcontroller and PC projects : tempr not working

Page 4 of 4

Author

Message

Peter63
Senior Member

Joined: 28/07/2017
Location: Sweden
Posts: 196

Posted: 05:35am 30 May 2026

Copy link to clipboard

Print this post

Jepp

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 2069

Posted: 05:47am 30 May 2026

Copy link to clipboard

Print this post

Well I decided to setup my 2040 Zero with that ili9488 now it's free and gave this DS1820 code a go, now I was having no luck so went back to the start of this thread and saw Tempr(GP9,500) was the fix to get the DS1820 working.

Now when I run the code.

50
Temp = 680°C
50
Temp = 680°C
50
Temp = 680°C
50
Temp = 680°C
50
Temp = 680°C
50
Temp = 680°C
50
Temp = 680°C
50
Temp = 680°C
50
Temp = 154°C
50
Temp = 154°C
50
Temp = 154°C
50
> ? tempr (Gp9, 500)
19.25
>

Nothing changed in the code just copied it and pasted into MMEdit. Anyway the good thing the DS1820 looks to be working

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 06:13am 31 May 2026

Copy link to clipboard

Print this post

Ok, so if you don't know which DS18x20 you have these two functions should work with any, including slow ones.
In the first one you can optionally set the Conversion Time in mS.
Usage:-
Print DS18x20ct(mm.info(pinno GPxx)) ' the default Conversion Time is 750mS
or
Print DS18x20ct(mm.info(pinno GPxx, mS_delay) '1000mS should cover most.

The second doesn't need it as it checks if the conversion is finished before reading. If not finished it returns to the main loop.
After reading it starts a new conversion, whish happens in the background as it returns to the main loop.
Usage:-
Print DS18x20(mm.info(pinno GPxx))

Function DS18x20ct(PinNbr As INTEGER, Delay As INTEGER) As FLOAT
' derived from DS18x20 test code by TassyJim
Local INTEGER T1,T2,T3,CpC,F
OneWire WRITE PinNbr,1,1,&h33 'read "family" ROM code
OneWire READ PinNbr,0,1,F ':Print F, "16=DS1820/DS18S20, 32=DS18S22, 40=DS18B20",
OneWire RESET PinNbr ' reset before command
OneWire WRITE PinNbr, 8, 2, &hCC, &h44 ' start conversion, adjust for slow units
If Delay < 10 then Delay = 750 ' maximum normal conversion time
Pause Delay
OneWire RESET PinNbr ' reset before command
OneWire WRITE PinNbr, 1, 2, &hCC, &hBE ' command read data
OneWire READ PinNbr, 0, 8, T1,T2,T3,T3,T3,T3,T3,CpC 'get the data
'process the data
If F=16 Then DS18x20ct = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 -0.25 + (CpC-T3)/CpC
If F=40 or F=34 Then DS18x20ct = Str2bin(int16,Chr$(T1)+Chr$(T2))/16
End Function

PinNbr = MM.Info(pinno GP7)
Dim DStemp = DS18x20(PinNbr) 'purge old data and start new conversion
Dim integer n

Do 'Main Loop
t = timer
Print n;
DStemp = DS18x20(PinNbr) 'get Temp, if ready
If DStemp <> 1000 Then
Print
Print "Temp =";DStemp;"`C"
n = 0
EndIf
Do : Loop until Timer > 49.9
inc n,50
Loop

Function DS18x20(PinNbr As INTEGER) As FLOAT
' Adapted from DS18x20 test code by TassyJim
Local INTEGER done, T1, T2, T3, CpC, F
DS18x20 = 1000 ' standard error code
OneWire READ PinNbr, 4, 1, done ' is conversion finished?
If done = 0 Then Exit Function ' if not return to program
'Get the data
OneWire WRITE PinNbr,1,1,&h33 'read "family" ROM code
OneWire READ PinNbr,0,1,F ':Print F; " 16=DS1820/DS18S20, 32=DS18S22, 40=DS18B20",
OneWire RESET PinNbr ' reset before command
OneWire WRITE PinNbr, 1, 2, &hCC, &hBE ' command read data
OneWire READ PinNbr, 0, 8, T1,T2,T3,T3,T3,T3,T3,CpC ' get the data
' process the data
If F=16 Then Value = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 -0.25 + (CpC-T3)/CpC
If F=40 or F=34 Then Value = Str2bin(int16,Chr$(T1)+Chr$(T2))/16
DS18x20 = Cint(Value * 10) / 10 'round to 1/10ths

'Start conversion, ready for next read
OneWire RESET PinNbr ' reset before command
OneWire WRITE PinNbr, 8, 2, &hCC, &h44 ' start conversion
End Function
End

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 2069

Posted: 07:00am 31 May 2026

Copy link to clipboard

Print this post

Thanks for that Phil

just tried it

Temp = 85°C
50
Temp = 85°C
50
Temp = 85°C
50
Temp = 85°C
50
Temp = 85°C
50
Temp = 85°C
50
Temp = 85°C
50
Temp = 85°C
50
Temp = 18.1°C
50
Temp = 18.1°C
50
Temp = 18.1°C
50
Temp = 18.1°C
50
Temp = 18.1°C
50

I did get these sealed can temp sensors about 15-16 years ago so they may be DS1820's that need the delay for it to work.

Anyway it is time to make a new thread with my project for the temp sensor.

Regards Bryan

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 12:32pm 31 May 2026

Copy link to clipboard

Print this post

Have been puzzled by your output only showing "50" between reads. Each 50 is 50mS so you should get something like this.

50 100 150 200 250 300 350 400 450 500
Temp = 19.2`C
50 100 150 200 250 300 350 400 450 500
Temp = 19.3`C

Then when I tried a non-genuine DS18B20 I got the same as you. Further investigation showed it says it has completed the temperature conversion in 33mS.
But it hasn't actually finished so the data you get is from a previous read.
That is why you got a string of 85°C readings, then the correct temp.

For these non-genuine units you are better off using the MMBasic TEMPR START GPxx,3 before the TEMPR(GPxx) function. The ",3" gives maximum resolution and ensures TEMPR(GPxx) waits long enough before reading.

The example above shows TEMPR(GPxx) immediately following TEMPR START but it doesn't need to. You can put other code between to make use of the 600mS or so it takes to do a conversion.
Edited 2026-06-01 08:00 by phil99

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 10:56pm 31 May 2026

Copy link to clipboard

Print this post

More experimenting with the nongenuine DS18B20.

It's conversion time is much faster than for the genuine unit.
It does high res 1/16° conversions in less than 34mS.
With the temperature changing rapidly it really does get new values that fast.

It's accuracy, however appears to be a little less, almost 1° high compared to a genuine unit and a pair of AHT10s.

Edit.

> 'Non-genuine DS18B20
> t2=timer:OneWire WRITE 9,1,2,204,68:t=timer:do:OneWire READ 9,4,1,d:loop until d :? timer-t,timer-t2
33.237 35.562
> ' So about 2.3mS to start conversion and 33.3mS to carry it out.
>'genuine DS18B20
> t2=timer:OneWire WRITE 10,1,2,204,68:t=timer:do:OneWire READ 10,4,1,d:loop until d:?timer-t,timer-t2
479.366 481.694
>

Edited 2026-06-01 11:09 by phil99

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 08:57am 02 Jun 2026

Copy link to clipboard

Print this post

A number of DS18x20 can run from the same OneWire bus by using the unique ROM code each contains.
The codes can be read by copying and pasting the command lines below into TeraTerm.
Only one device may be on the bus while reading the code. Ignore the output numbers in the example

> clear : dim integer q,w,e,r,t,y,u,i,ROM, PinNo=mm.info(pinno GP6)
> OneWire Reset PinNo : OneWire WRITE PinNo,1,1,&h33 : OneWire READ PinNo,2,8,q,w,e,r,t,y,u,i : ? ,q,w,e,r,t,y,u,i
40 63 68 87 4 225 60 77
> RC$ = chr$(q)+chr$(w)+chr$(e)+chr$(r)+chr$(t)+chr$(y)+chr$(u)+chr$(i) : ROM = str2bin(Uint64,RC$,big) :? ROM
2900111825584602189
>

Its a bit clunky but OneWire doesn't use arrays or strings.

Insert your ROM code numbers and OneWire pin number in the program below. This example is for two but could be modified for more.

' running 2 DS18x20 sensors on the same pin. Get their ROM codes an replace those below
Dim PinNbr = MM.Info(pinno gp6)
Dim integer n, ROMcode(1) = (2909716863767585976, 2900111825584602189)

Dim DStemp0 = DS18x20(PinNbr, ROMcode(0)) 'purge old data and start new conversion
Dim DStemp1 = DS18x20(PinNbr, ROMcode(1)) 'purge old data and start new conversion

Do ' Main Loop
D = DS18x20(PinNbr, ROMcode(n))
If D<>1000 Then Print "Device";n; D;"`C",
If n=1 Then Print
Pause 1000
n = Not n
Loop

Function DS18x20(PinNbr As INTEGER, ROM As INTEGER) As FLOAT
' Adapted from DS18x20 test code by TassyJim
Local INTEGER done, T1, T2, T3, CpC, Fam, a,b,c,d,e,f,g,h
DS18x20 = 1000' standard error code
OneWire READ PinNbr, 4, 1, done' is conversion finished?
If done = 0 Then Exit Function ' if not return to program

If ROM Then
a=ROM>>56 : b=ROM>>48 And 255 : c=ROM>>40 And 255 : d=ROM>>32 And 255
e=ROM>>24 And 255 : f=ROM>>16 And 255 : g=ROM>>8 And 255 : h=ROM And 255
Fam=a ': Print a,b,c,d,e,f,g,h
OneWire WRITE PinNbr,1,1,&h55 ' reset then match ROM Code command
OneWire WRITE PinNbr,0,8,a,b,c,d,e,f,g,h ' send ROM Code
OneWire WRITE 9,0,1,&hBE ' read scratchpad command
OneWire READ 9, 0, 8, T1,T2,T3,T4,T5,T6,T7,CpC' get the data
Else
OneWire WRITE PinNbr,1,1,&h33 ' read "family" ROM code
OneWire READ PinNbr,0,1,Fam
EndIf

' process the data 16=DS1820/DS18S20, 32=DS18S22, 40=DS18B20
If Fam = 16 Then Value = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 -0.25+(CpC-T3)/CpC
If Fam = 40 Or Fam = 34 Then Value = Str2bin(int16,Chr$(T1)+Chr$(T2))/16
DS18x20 = Cint(Value * 100) / 100 'round to 1/100ths

' Start conversion, ready for next read
If ROM Then
OneWire WRITE PinNbr,1,1,&h55 'reset then match ROM Code command
OneWire WRITE PinNbr,0,8,a,b,c,d,e,f,g,h 'send ROM Code
OneWire WRITE PinNbr,2,1,&h44 'Master issues Convert Temp. command
Else
OneWire RESET PinNbr' ' reset before command
OneWire WRITE PinNbr, 8, 2, &hCC, &h44' ' start conversion
EndIf
End Function
End

Footnote added 2026-06-02 21:49 by phil99
A sample of the output.

Device 0 24.19`C Device 1 31.69`C
Device 0 23.38`C Device 1 31.56`C
Device 0 22.69`C Device 1 31.44`C
Device 0 22.13`C Device 1 31.25`C
Device 0 21.63`C Device 1 31.13`C
Device 0 21.25`C Device 1 31`C
Device 0 20.88`C Device 1 30.88`C
Device 0 20.63`C Device 1 30.75`C
Device 0 20.38`C Device 1 30.63`C
Device 0 20.19`C Device 1 30.5`C

Footnote added 2026-06-02 22:01 by phil99
Noticed a copy/paste error tat would affect the fractions of degrees for DS18S20 sensors.
Replace this line:-
OneWire READ 9, 0, 8, T1,T2,T3,T4,T5,T6,T7,CpC' get the data
with
OneWire READ 9, 0, 8, T1,T2,T3,T3,T3,T3,T3,CpC' get the data

Most of the T3s are dummys, only the one before CpC gives the fractions.

matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 11435

Posted: 10:05am 02 Jun 2026

Copy link to clipboard

Print this post

phil99: what firmware version are you using? I'll post an update with flexible onewire data parameters for you to test

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 10:56am 02 Jun 2026

Copy link to clipboard

Print this post

PicoMiteVGA MMBasic RP2350A Edition V6.03.00RC12

Or plain RP2040 would also do.

Thanks very much for considering this.

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 05:39am 03 Jun 2026

Copy link to clipboard

Print this post

The latest PicoMite firmware - V6.03.00RC15 can now use strings and arrays in OneWire commands.
Here is the previous program converted to use both. A more streamlined result and simpler to write.

' Running 2 DS18x20 sensors on the same pin. Get their ROM codes and replace those below.
Dim PinNbr = MM.Info(pinno gp6)
Dim integer n=0, ROMcode(1) = (2909716863767585976, 2900111825584602189)

Dim DStemp0 = DS18x20(PinNbr, ROMcode(0)) 'purge old data and start new conversion
Pause 750
Dim DStemp1 = DS18x20(PinNbr, ROMcode(1)) 'purge old data and start new conversion

Do ' Main Loop
D = DS18x20(PinNbr, ROMcode(n))
If D<>1000 Then Print "Device";n; D;"`C",
If n=1 Then Print
Pause 1000
n = Not n
Loop

Function DS18x20(PinNbr As INTEGER, ROM As INTEGER) As FLOAT
' Adapted from DS18x20 test code by TassyJim
' This version for MMbasic v6.03.00RC15 with array and string support for OneWire
  Local INTEGER done, T(7), Fam = ROM >> 56 'get family code from ROM code
  Local ROMcode$ = Bin2str$(Uint64,ROM,big) 'convert ROM code to string
  DS18x20 = 1000' standard error code
  OneWire READ PinNbr, 4, 1, done' is conversion finished?
  If Not done Then Exit Function ' if not return to program

  If ROM Then
   OneWire WRITE PinNbr, 1, 1, &h55 ' reset then match ROM Code command
   OneWire WRITE PinNbr, 0, 8, ROMcode$ ' send ROM Code to the DS18x20
   OneWire WRITE PinNbr, 0, 1, &hBE ' read scratchpad command
   Else
   OneWire WRITE PinNbr,1,1,&h33 'If no ROM code given assume only one DS18x20 connected
   OneWire READ PinNbr, 0, 1, Fam ' read "family" ROM code
   OneWire WRITE PinNbr, 1, 2, &hCC, &hBE ' command read data
  EndIf
  OneWire READ PinNbr, 0, 8, T() ': Math V_Print T()' get the data

' process the data. Fam = Family ROM codes - 16=DS1820/DS18S20, 34=DS18S22, 40=DS18B20
  If Fam = 16 Then Value = Str2bin(int16,Chr$(T(0))+Chr$(T(1))\2 -0.25+(T(7)-T(6))/T(7))
  If Fam = 40 Or Fam = 34 Then Value = Str2bin(int16,Chr$(T(0))+Chr$(T(1)))/16
  DS18x20 = Cint(Value * 100) / 100 'round to 1/100ths

' Start conversion, ready for next read
  If ROM Then
   OneWire WRITE PinNbr, 1, 1, &h55 'reset then match ROM Code command
   OneWire WRITE PinNbr, 0, 8, ROMcode$ 'send ROM Code
   OneWire WRITE PinNbr, 2, 1, &h44 'Master issues Convert Temp. command
   Else
   OneWire RESET PinNbr' ' reset before command
  OneWire WRITE PinNbr, 8, 2, &hCC, &h44' ' start conversion
  EndIf
End Function
End

Output.

Device 0 13.06`C Device 1 22.56`C
Device 0 23`C Device 1 22.56`C
Device 0 23.06`C Device 1 22.56`C
Device 0 23.06`C Device 1 22.56`C
Device 0 23.06`C Device 1 22.5`C

Reading the ROM codes is simpler too.

> clear : dim integer ROM, PinNo=mm.info(pinno GP6)
> OneWire WRITE PinNo, 1, 1, &h33 : OneWire READ PinNo, 2, 8, RC$
> ROM = str2bin(Uint64,RC$,big) : ? ROM
2909716863767585976
>

Edited 2026-06-03 23:01 by phil99

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 05:05am 04 Jun 2026

Copy link to clipboard

Print this post

Attempts to get the DS18B20s to work in Parasite Power mode have failed so here is a hardware solution that does work.

The component values are not critical, try whatever you have. I have also tested 1.2kΩ and 10µF powering two DS18B20s.

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3268

Posted: 01:09pm 05 Jun 2026

Copy link to clipboard

Print this post

Yet another tweak.
As before many DS18x20s can be on the OneWire bus if the unique ROM code of each is provided.
If no ROM code is provided it assumes there is only one device on the bus and reads the temperature and reads its unique ROM code.
The ROM code and Family code are then available in the global variables ROM_Code% and Family%. If your program uses OPTION EXPLICIT you will need to Dim them, if you are not supplying the ROM codes every time you call the function.

Command line usage:-

> clear : PinNo = mm.info(pinno GP6) : ? ds18x20(9,2900111825584602189)
21.375
>
> clear : PinNo = mm.info(pinno GP6) : ? ds18x20(PinNo), ROM_Code%, Family%
21.4375 2900111825584602189 40
>

Function DS18x20(PinNbr As INTEGER, ROM As INTEGER) As FLOAT
' Adapted from DS18x20 test code by TassyJim
' This version for MMbasic v6.03.00RC15 with array and string support for OneWire
Local INTEGER done, T(7), Fam
Local ROMcode$ = Bin2str$(Uint64,ROM,big) 'convert ROM code to string
DS18x20 = 1000' standard error code
If ROM > -1 Then
Fam = ROM >> 56
OneWire READ PinNbr, 4, 1, done' is conversion finished?
If Not done Then Exit Function ' if not return to program
EndIf

If ROM > 0 Then
OneWire WRITE PinNbr, 1, 1, &h55 ' reset then match ROM Code command
OneWire WRITE PinNbr, 0, 8, ROMcode$ ' send ROM Code to the DS18x20
OneWire WRITE PinNbr,0,1,&hBE ' read scratchpad command
Else
OneWire WRITE PinNbr, 1, 1, &h33 'If no ROM code given assume only one DS18x20 connected
OneWire READ PinNbr, 0, 8, ROMcode$ ' Read the ROM code
OneWire WRITE PinNbr, 1, 2, &hCC, &hBE ' read data command
ROM_Code% = Str2bin(Uint64,ROMcode$,big) ' Output the ROM code to a Global variable
Fam = ROM_Code% >> 56 : Family% = Fam ' extract "family" code to a Global
EndIf
OneWire READ PinNbr, 0, 8, T() ' : Math V_Print T()' get the temperature data

' process the data, Family ROM codes - 16=DS1820/DS18S20, 34=DS18S22, 40=DS18B20
If Fam = 16 Then Value = Str2bin(int16,Chr$(T(0))+Chr$(T(1))\2 -0.25+(T(7)-T(6))/T(7))
If Fam = 40 Or Fam = 34 Then Value = Str2bin(int16,Chr$(T(0))+Chr$(T(1)))/16
If Fam = 0 Then Value = 1001
DS18x20 = Value 'round to 1/100ths

' Start conversion, ready for next read
If ROM Then
OneWire WRITE PinNbr, 1, 1, &h55 'reset then match ROM Code command
OneWire WRITE PinNbr, 0, 8, ROMcode$ 'send ROM Code
OneWire WRITE PinNbr, 8, 1, &h44 'Master issues Convert Temp. command
Else
OneWire RESET PinNbr' ' reset before command
OneWire WRITE PinNbr, 8, 2, &hCC, &h44' ' start conversion
EndIf
' Print "conversion started"
End Function

Page 4 of 4

Print this page

To reply to this topic, you need to log in.