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Posted: 04:01pm 29 May 2026 Copy link to clipboard	Peter63 Senior Member

here comes a new run with cooling spray...

T1 175 T2 255 T3 5 Test1 =-40.5 Test2 =-39.5625 Test3 =-39.5625 Test4 =-39.375 Test5 =-39.375
Temp =-39.375`C
T1 173 T2 255 T3 6 Test1 =-41.5 Test2 =-40.625 Test3 =-40.625 Test4 =-40.4375 Test5 =-40.4375
Temp =-40.4375`C
T1 173 T2 255 T3 3 Test1 =-41.5 Test2 =-40.4375 Test3 =-40.4375 Test4 =-40.25 Test5 =-40.25
Temp =-40.25`C
T1 174 T2 255 T3 9 Test1 =-41 Test2 =-40.8125 Test3 =-40.8125 Test4 =-40.625 Test5 =-40.625
Temp =-40.625`C
T1 175 T2 255 T3 2 Test1 =-40.5 Test2 =-39.375 Test3 =-39.375 Test4 =-39.1875 Test5 =-39.1875
Temp =-39.1875`C
T1 176 T2 255 T3 10 Test1 =-40 Test2 =-39.875 Test3 =-39.875 Test4 =-39.6875 Test5 =-39.6875
Temp =-39.6875`C
T1 178 T2 255 T3 12 Test1 =-39 Test2 =-39 Test3 =-39 Test4 =-38.8125 Test5 =-38.8125
Temp =-38.8125`C
T1 183 T2 255 T3 4 Test1 =-36.5 Test2 =-35.5 Test3 =-35.5 Test4 =-35.3125 Test5 =-35.3125
Temp =-35.3125`C
T1 193 T2 255 T3 4 Test1 =-31.5 Test2 =-30.5 Test3 =-30.5 Test4 =-30.3125 Test5 =-30.3125
Temp =-30.3125`C
T1 205 T2 255 T3 3 Test1 =-25.5 Test2 =-24.4375 Test3 =-24.4375 Test4 =-24.25 Test5 =-24.25
Temp =-24.25`C
T1 215 T2 255 T3 2 Test1 =-20.5 Test2 =-19.375 Test3 =-19.375 Test4 =-19.1875 Test5 =-19.1875
Temp =-19.1875`C
T1 224 T2 255 T3 12 Test1 =-16 Test2 =-16 Test3 =-16 Test4 =-15.8125 Test5 =-15.8125
Temp =-15.8125`C
T1 232 T2 255 T3 16 Test1 =-12 Test2 =-12.25 Test3 =-12.25 Test4 =-12.0625 Test5 =-12.0625
Temp =-12.0625`C
T1 238 T2 255 T3 15 Test1 =-9 Test2 =-9.1875 Test3 =-9.1875 Test4 =-9 Test5 =-9
Temp =-9`C
T1 243 T2 255 T3 7 Test1 =-6.5 Test2 =-5.6875 Test3 =-5.6875 Test4 =-5.5 Test5 =-5.5
Temp =-5.5`C
T1 247 T2 255 T3 4 Test1 =-4.5 Test2 =-3.5 Test3 =-3.5 Test4 =-3.3125 Test5 =-3.3125
Temp =-3.3125`C
T1 251 T2 255 T3 6 Test1 =-2.5 Test2 =-1.625 Test3 =-1.625 Test4 =-1.4375 Test5 =-1.4375
Temp =-1.4375`C
T1 254 T2 255 T3 15 Test1 =-1 Test2 =-1.1875 Test3 =-1.1875 Test4 =-1 Test5 =-1
Temp =-1`C
T1 255 T2 255 T3 1 Test1 =-0.5 Test2 = 0.6875 Test3 = 0.6875 Test4 = 0.875 Test5 = 0.875
Temp = 0.875`C
T1 0 T2 0 T3 12 Test1 = 0 Test2 = 0 Test3 = 0 Test4 = 0.1875 Test5 = 0.1875
Temp = 0.1875`C
T1 1 T2 0 T3 2 Test1 = 0.5 Test2 = 0.625 Test3 = 0.625 Test4 = 0.8125 Test5 = 0.8125
Temp = 0.8125`C
T1 3 T2 0 T3 3 Test1 = 1.5 Test2 = 1.5625 Test3 = 1.5625 Test4 = 1.75 Test5 = 1.75
Temp = 1.75`C
T1 6 T2 0 T3 16 Test1 = 3 Test2 = 2.75 Test3 = 2.75 Test4 = 2.9375 Test5 = 2.9375
Temp = 2.9375`C
T1 8 T2 0 T3 13 Test1 = 4 Test2 = 3.9375 Test3 = 3.9375 Test4 = 4.125 Test5 = 4.125
Temp = 4.125`C
T1 10 T2 0 T3 11 Test1 = 5 Test2 = 5.0625 Test3 = 5.0625 Test4 = 5.25 Test5 = 5.25
Temp = 5.25`C
T1 12 T2 0 T3 11 Test1 = 6 Test2 = 6.0625 Test3 = 6.0625 Test4 = 6.25 Test5 = 6.25
Temp = 6.25`C
T1 14 T2 0 T3 14 Test1 = 7 Test2 = 6.875 Test3 = 6.875 Test4 = 7.0625 Test5 = 7.0625
Temp = 7.0625`C
T1 15 T2 0 T3 3 Test1 = 7.5 Test2 = 7.5625 Test3 = 7.5625 Test4 = 7.75 Test5 = 7.75
Temp = 7.75`C
T1 17 T2 0 T3 7 Test1 = 8.5 Test2 = 8.3125 Test3 = 8.3125 Test4 = 8.5 Test5 = 8.5
Temp = 8.5`C
T1 18 T2 0 T3 12 Test1 = 9 Test2 = 9 Test3 = 9 Test4 = 9.1875 Test5 = 9.1875
Temp = 9.1875`C
T1 20 T2 0 T3 14 Test1 = 10 Test2 = 9.875 Test3 = 9.875 Test4 = 10.0625 Test5 = 10.0625
Temp = 10.0625`C
T1 21 T2 0 T3 6 Test1 = 10.5 Test2 = 10.375 Test3 = 10.375 Test4 = 10.5625 Test5 = 10.5625
Temp = 10.5625`C
T1 22 T2 0 T3 12 Test1 = 11 Test2 = 11 Test3 = 11 Test4 = 11.1875 Test5 = 11.1875
Temp = 11.1875`C
T1 23 T2 0 T3 5 Test1 = 11.5 Test2 = 11.4375 Test3 = 11.4375 Test4 = 11.625 Test5 = 11.625
Temp = 11.625`C
T1 24 T2 0 T3 16 Test1 = 12 Test2 = 11.75 Test3 = 11.75 Test4 = 11.9375 Test5 = 11.9375
Temp = 11.9375`C
T1 24 T2 0 T3 11 Test1 = 12 Test2 = 12.0625 Test3 = 12.0625 Test4 = 12.25 Test5 = 12.25
Temp = 12.25`C
T1 25 T2 0 T3 7 Test1 = 12.5 Test2 = 12.3125 Test3 = 12.3125 Test4 = 12.5 Test5 = 12.5
Temp = 12.5`C
T1 25 T2 0 T3 3 Test1 = 12.5 Test2 = 12.5625 Test3 = 12.5625 Test4 = 12.75 Test5 = 12.75
Temp = 12.75`C
T1 26 T2 0 T3 15 Test1 = 13 Test2 = 12.8125 Test3 = 12.8125 Test4 = 13 Test5 = 13
Temp = 13`C
T1 26 T2 0 T3 12 Test1 = 13 Test2 = 13 Test3 = 13 Test4 = 13.1875 Test5 = 13.1875
Temp = 13.1875`C
T1 26 T2 0 T3 9 Test1 = 13 Test2 = 13.1875 Test3 = 13.1875 Test4 = 13.375 Test5 = 13.375
Temp = 13.375`C
T1 27 T2 0 T3 6 Test1 = 13.5 Test2 = 13.375 Test3 = 13.375 Test4 = 13.5625 Test5 = 13.5625
Temp = 13.5625`C
T1 27 T2 0 T3 2 Test1 = 13.5 Test2 = 13.625 Test3 = 13.625 Test4 = 13.8125 Test5 = 13.8125
Temp = 13.8125`C
T1 28 T2 0 T3 16 Test1 = 14 Test2 = 13.75 Test3 = 13.75 Test4 = 13.9375 Test5 = 13.9375
Temp = 13.9375`C
T1 28 T2 0 T3 13 Test1 = 14 Test2 = 13.9375 Test3 = 13.9375 Test4 = 14.125 Test5 = 14.125
Temp = 14.125`C
T1 28 T2 0 T3 11 Test1 = 14 Test2 = 14.0625 Test3 = 14.0625 Test4 = 14.25 Test5 = 14.25
Temp = 14.25`C
T1 28 T2 0 T3 9 Test1 = 14 Test2 = 14.1875 Test3 = 14.1875 Test4 = 14.375 Test5 = 14.375
Temp = 14.375`C
T1 29 T2 0 T3 6 Test1 = 14.5 Test2 = 14.375 Test3 = 14.375 Test4 = 14.5625 Test5 = 14.5625
Temp = 14.5625`C
T1 29 T2 0 T3 4 Test1 = 14.5 Test2 = 14.5 Test3 = 14.5 Test4 = 14.6875 Test5 = 14.6875
Temp = 14.6875`C
T1 29 T2 0 T3 2 Test1 = 14.5 Test2 = 14.625 Test3 = 14.625 Test4 = 14.8125 Test5 = 14.8125
Temp = 14.8125`C
T1 30 T2 0 T3 16 Test1 = 15 Test2 = 14.75 Test3 = 14.75 Test4 = 14.9375 Test5 = 14.9375
Temp = 14.9375`C
T1 30 T2 0 T3 13 Test1 = 15 Test2 = 14.9375 Test3 = 14.9375 Test4 = 15.125 Test5 = 15.125
Temp = 15.125`C
T1 30 T2 0 T3 12 Test1 = 15 Test2 = 15 Test3 = 15 Test4 = 15.1875 Test5 = 15.1875
Temp = 15.1875`C
T1 30 T2 0 T3 10 Test1 = 15 Test2 = 15.125 Test3 = 15.125 Test4 = 15.3125 Test5 = 15.3125
Temp = 15.3125`C
T1 31 T2 0 T3 8 Test1 = 15.5 Test2 = 15.25 Test3 = 15.25 Test4 = 15.4375 Test5 = 15.4375
Temp = 15.4375`C
T1 31 T2 0 T3 6 Test1 = 15.5 Test2 = 15.375 Test3 = 15.375 Test4 = 15.5625 Test5 = 15.5625
Temp = 15.5625`C
T1 31 T2 0 T3 3 Test1 = 15.5 Test2 = 15.5625 Test3 = 15.5625 Test4 = 15.75 Test5 = 15.75
Temp = 15.75`C
T1 31 T2 0 T3 2 Test1 = 15.5 Test2 = 15.625 Test3 = 15.625 Test4 = 15.8125 Test5 = 15.8125
Temp = 15.8125`C
T1 32 T2 0 T3 10 Test1 = 16 Test2 = 16.125 Test3 = 16.125 Test4 = 16.3125 Test5 = 16.3125
Temp = 16.3125`C
T1 34 T2 0 T3 14 Test1 = 17 Test2 = 16.875 Test3 = 16.875 Test4 = 17.0625 Test5 = 17.0625
Temp = 17.0625`C
T1 35 T2 0 T3 2 Test1 = 17.5 Test2 = 17.625 Test3 = 17.625 Test4 = 17.8125 Test5 = 17.8125
Temp = 17.8125`C
T1 35 T2 0 T3 2 Test1 = 17.5 Test2 = 17.625 Test3 = 17.625 Test4 = 17.8125 Test5 = 17.8125
Temp = 17.8125`C
T1 35 T2 0 T3 2 Test1 = 17.5 Test2 = 17.625 Test3 = 17.625 Test4 = 17.8125 Test5 = 17.8125
Temp = 17.8125`C
T1 35 T2 0 T3 3 Test1 = 17.5 Test2 = 17.5625 Test3 = 17.5625 Test4 = 17.75 Test5 = 17.75
Temp = 17.75`C
T1 35 T2 0 T3 2 Test1 = 17.5 Test2 = 17.625 Test3 = 17.625 Test4 = 17.8125 Test5 = 17.8125
Temp = 17.8125`C
T1 35 T2 0 T3 1 Test1 = 17.5 Test2 = 17.6875 Test3 = 17.6875 Test4 = 17.875 Test5 = 17.875
Temp = 17.875`C
T1 41 T2 0 T3 3 Test1 = 20.5 Test2 = 20.5625 Test3 = 20.5625 Test4 = 20.75 Test5 = 20.75
Temp = 20.75`C
T1 41 T2 0 T3 2 Test1 = 20.5 Test2 = 20.625 Test3 = 20.625 Test4 = 20.8125 Test5 = 20.8125
Temp = 20.8125`C
T1 40 T2 0 T3 12 Test1 = 20 Test2 = 20 Test3 = 20 Test4 = 20.1875 Test5 = 20.1875
Temp = 20.1875`C
T1 40 T2 0 T3 15 Test1 = 20 Test2 = 19.8125 Test3 = 19.8125 Test4 = 20 Test5 = 20
Temp = 20`C
T1 46 T2 0 T3 11 Test1 = 23 Test2 = 23.0625 Test3 = 23.0625 Test4 = 23.25 Test5 = 23.25
Temp = 23.25`C
T1 49 T2 0 T3 1 Test1 = 24.5 Test2 = 24.6875 Test3 = 24.6875 Test4 = 24.875 Test5 = 24.875
Temp = 24.875`C
T1 47 T2 0 T3 1 Test1 = 23.5 Test2 = 23.6875 Test3 = 23.6875 Test4 = 23.875 Test5 = 23.875
Temp = 23.875`C
T1 46 T2 0 T3 13 Test1 = 23 Test2 = 22.9375 Test3 = 22.9375 Test4 = 23.125 Test5 = 23.125
Temp = 23.125`C

/Peter63

Posted: 10:55pm 29 May 2026 Copy link to clipboard	phil99 Guru

Thanks for the extra testing. It filled all the gaps in the T3 data which I now see goes from 16 to 1 with increasing temperature.
And that makes quite a difference. The equation in the datasheet does not appear to be correct.

The data you have given me should be enough to simulate a DS18S20 properly and find the correct equation. More to follow.

Edit.
This gives the most sensible results:-

DS18S20t = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 + (16 - T3)/16 -0.9375
'or
Value = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 + (16-T3)/16 -0.9375

And also appears to work below zero.
Edited 2026-05-30 12:26 by phil99

Posted: 01:44am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

photo of the DS18S20 marking used during test

/Peter63

Posted: 02:41am 30 May 2026 Copy link to clipboard	phil99 Guru

The two programs with the updated equation.

Function DS18S20(PinNbr As INTEGER) As FLOAT
' derived from DS18x20 test code by TassyJim
Local INTEGER T1,T2,T3

OneWire RESET PinNbr ' reset before command
OneWire WRITE PinNbr, 8, 2, &hCC, &h44 ' start conversion
Pause 750 ' maximum conversion time
OneWire RESET PinNbr ' reset before command
OneWire WRITE PinNbr, 1, 2, &hCC, &hBE ' command read data
OneWire READ PinNbr, 0, 7, T1,T2,T3,T3,T3,T3,T3 'get the data

DS18S20t = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 + (16-T3)/16 -0.9375 'process the data
End Function

PinNbr = MM.Info(pinno GP7)
Dim n = 0
Dim DStemp = DS18S20(PinNbr) 'purge old data and start new conversion

Do 'Main Loop
t = timer
Print n;
DStemp = DS18S20(PinNbr) 'get Temp, if ready
If DStemp <> 1000 Then
Print
Print "Temp =";DStemp;"`C"
n = 0
EndIf
Do : Loop until Timer - t > 49.9
Inc n,50
Loop

Function DS18S20(PinNbr As INTEGER) As FLOAT
' Adapted from DS18x20 test code by TassyJim
Local INTEGER done, T1, T2, T3
DS18S20 = 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 RESET PinNbr ' reset before command
OneWire WRITE PinNbr, 1, 2, &hCC, &hBE ' command read data
OneWire READ PinNbr, 0, 7, T1,T2,T3,T3,T3,T3,T3 'get the data

Value = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 + (16-T3)/16 -0.9375 'process the data
DS18S20 = 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

Posted: 03:29am 30 May 2026 Copy link to clipboard	TassyJim Guru

The COUNT PER °C scratchpad is supposed be always 16 with the DS18S20 but Peter has a DS1820 according to the photo.
Are you sure that COUNT PER °C is always 16 with the DS1820?

I don't have either chip to test with.

Jim

Posted: 03:34am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

A little test again then with cooling spray, seems to be working fine now.

> run
0 50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-36.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-36.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-35.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-35.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-35`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-35.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-34.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-34.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-34.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-34.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-30.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-29`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-27.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-25.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-24.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-22.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-21.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-19.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-17.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-12.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-5.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 0.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 5.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 9.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 12.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 15.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 16.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 18.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 20.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 21.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 21.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 21.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 23.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 24.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 24.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 24.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 24`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 24.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 25.9`C

Posted: 03:37am 30 May 2026 Copy link to clipboard	phil99 Guru

Jim, you are right, as you were writing that I was reading the Dallas DS1820 datasheet and COUNT PER °C varies according to an internal calibration table.

I will incorporate that and ask Peter63 to test again.

The saga continues...

Peter, those results do look more promising.
Edited 2026-05-30 13:40 by phil99

Posted: 03:38am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

I thought I had a DS18S20, according to my saved label, but now it doesn't seem to be so.

Happy to test further...
Edited 2026-05-30 14:01 by Peter63

Posted: 04:06am 30 May 2026 Copy link to clipboard	phil99 Guru

The last byte is COUNT_PER_C (CpC)
TEMPERATURE = TEMP_READ – 0.25 + (COUNT_PER_C – COUNT_REMAIN) / COUNT_PER_C

Function DS18S20(PinNbr As INTEGER) As FLOAT
' derived from DS18x20 test code by TassyJim
Local INTEGER T1,T2,T3,CpC

OneWire RESET PinNbr ' reset before command
OneWire WRITE PinNbr, 8, 2, &hCC, &h44 ' start conversion
Pause 750 ' maximum conversion time
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

DS18S20t = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 -0.25 + (CpC-T3)/CpC 'process the data
End Function

PinNbr = MM.Info(pinno GP7)
Dim n = 0
Dim DStemp = DS18S20(PinNbr) 'purge old data and start new conversion

Do 'Main Loop
t = timer
Print n;
DStemp = DS18S20(PinNbr) 'get Temp, if ready
If DStemp <> 1000 Then
Print
Print "Temp =";DStemp;"`C"
n = 0
EndIf
Do : Loop until Timer - t > 49.9
Inc n,50
Loop

Function DS18S20(PinNbr As INTEGER) As FLOAT
' Adapted from DS18x20 test code by TassyJim
Local INTEGER done, T1, T2, T3, CpC
DS18S20 = 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 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

Value = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 -0.25 + (CpC-T3)/CpC 'process the data
DS18S20 = 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

Edit.
Corrected a few typos in code above.
If you are already using it please copy it again.
Edited 2026-05-30 14:13 by phil99

Posted: 04:19am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

new test...

> run
0 50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-33.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-31.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-31.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-31.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-31.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-32`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-30.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-30.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-30.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-27.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-22.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-20.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-17.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-16.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-15.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-12.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-11.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-9.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-8.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-6.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-6.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-3.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-2.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-1.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp =-0.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 0.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 0.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 0.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 1.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 1.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 2.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 2.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 3.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 4.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 4.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 5.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 6.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 7.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 8.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 10.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 11.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 14.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 15.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 15.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 17.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 18.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 19.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 19.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 19.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 19.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 19.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 20.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 22`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 22.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 22.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 22.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650
Temp = 22.1`C

Posted: 04:27am 30 May 2026 Copy link to clipboard	TassyJim Guru

Can you alter the program to also print out CpC for each temperature.
IT will be interesting to see if it does remain at 16 over the full range. If it does change, you definitely do have DS1820, not DS18S20

Jim

Posted: 04:33am 30 May 2026 Copy link to clipboard	phil99 Guru

This addition should do it.

OneWire READ PinNbr, 0, 8, T1,T2,T3,T3,T3,T3,T3,CpC 'get the data
Print "T1=";T1,"T2=";T2,"T3=";T3,"CpC=";CpC,,
Value = Str2bin(int16,Chr$(T1)+Chr$(T2))\2 -0.25 + (CpC-T3)/CpC 'process the data

And note, there were typos in my last post that have been corrected.
Edited 2026-05-30 14:36 by phil99

Posted: 04:37am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

> run
CpC = 16 0 50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-25.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-25.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-25.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-26.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-26.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-25.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-24.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-23.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-21.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-19.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-14.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-6.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp =-2.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp = 1.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp = 6.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp = 11.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp = 15.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp = 18.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp = 19.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650 CpC = 16
Temp = 20.3`C

Posted: 04:45am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

new test T-value... and CpC

50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 204 T2= 255 T3= 16 CpC= 16
Temp =-26.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 204 T2= 255 T3= 16 CpC= 16
Temp =-26.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 204 T2= 255 T3= 11 CpC= 16
Temp =-25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 206 T2= 255 T3= 12 CpC= 16
Temp =-25`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 210 T2= 255 T3= 14 CpC= 16
Temp =-23.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 214 T2= 255 T3= 9 CpC= 16
Temp =-20.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 219 T2= 255 T3= 8 CpC= 16
Temp =-17.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 223 T2= 255 T3= 8 CpC= 16
Temp =-15.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 226 T2= 255 T3= 10 CpC= 16
Temp =-14.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 230 T2= 255 T3= 13 CpC= 16
Temp =-13.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 237 T2= 255 T3= 5 CpC= 16
Temp =-8.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 246 T2= 255 T3= 10 CpC= 16
Temp =-4.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 250 T2= 255 T3= 10 CpC= 16
Temp =-2.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 253 T2= 255 T3= 7 CpC= 16
Temp =-0.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 1 T2= 0 T3= 6 CpC= 16
Temp = 0.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 4 T2= 0 T3= 16 CpC= 16
Temp = 1.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 7 T2= 0 T3= 8 CpC= 16
Temp = 3.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 13 T2= 0 T3= 4 CpC= 16
Temp = 6.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 19 T2= 0 T3= 3 CpC= 16
Temp = 9.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 26 T2= 0 T3= 16 CpC= 16
Temp = 12.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 29 T2= 0 T3= 8 CpC= 16
Temp = 14.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 35 T2= 0 T3= 8 CpC= 16
Temp = 17.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 37 T2= 0 T3= 2 CpC= 16
Temp = 18.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 40 T2= 0 T3= 9 CpC= 16
Temp = 20.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 42 T2= 0 T3= 12 CpC= 16
Temp = 21`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 42 T2= 0 T3= 11 CpC= 16
Temp = 21.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 42 T2= 0 T3= 13 CpC= 16
Temp = 20.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 42 T2= 0 T3= 16 CpC= 16
Temp = 20.8`C

Posted: 04:53am 30 May 2026 Copy link to clipboard	phil99 Guru

CpC staying on 16 is what I would expect for a DS18S20, not DS1820.
The rate of change of temp. is so high it is hard to tell what the decimal part is doing.
To check that ideally we need a very slow change over about 2°C, while displaying T3 to get as much fine detail as possible.

Posted: 04:56am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

Could it be DS18S20 that I have, but maybe they are mislabeled?

Posted: 04:59am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

new test...

Temp = 23.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 47 T2= 0 T3= 6 CpC= 16
Temp = 23.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 47 T2= 0 T3= 5 CpC= 16
Temp = 23.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 47 T2= 0 T3= 5 CpC= 16
Temp = 23.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 47 T2= 0 T3= 4 CpC= 16
Temp = 23.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 47 T2= 0 T3= 2 CpC= 16
Temp = 23.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 47 T2= 0 T3= 2 CpC= 16
Temp = 23.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 47 T2= 0 T3= 1 CpC= 16
Temp = 23.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 16 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 16 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 16 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 47 T2= 0 T3= 1 CpC= 16
Temp = 23.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 16 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 16 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 16 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 15 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 15 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 15 CpC= 16
Temp = 23.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 14 CpC= 16
Temp = 23.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 13 CpC= 16
Temp = 23.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 11 CpC= 16
Temp = 24.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 48 T2= 0 T3= 9 CpC= 16
Temp = 24.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 49 T2= 0 T3= 7 CpC= 16
Temp = 24.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 49 T2= 0 T3= 4 CpC= 16
Temp = 24.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 49 T2= 0 T3= 3 CpC= 16
Temp = 24.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 49 T2= 0 T3= 1 CpC= 16
Temp = 24.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 50 T2= 0 T3= 16 CpC= 16
Temp = 24.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 50 T2= 0 T3= 15 CpC= 16
Temp = 24.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 50 T2= 0 T3= 13 CpC= 16
Temp = 24.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 50 T2= 0 T3= 13 CpC= 16
Temp = 24.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 50 T2= 0 T3= 12 CpC= 16
Temp = 25`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 50 T2= 0 T3= 11 CpC= 16
Temp = 25.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 50 T2= 0 T3= 10 CpC= 16
Temp = 25.1`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 50 T2= 0 T3= 9 CpC= 16
Temp = 25.2`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 51 T2= 0 T3= 8 CpC= 16
Temp = 25.3`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 51 T2= 0 T3= 6 CpC= 16
Temp = 25.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 51 T2= 0 T3= 5 CpC= 16
Temp = 25.4`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 51 T2= 0 T3= 4 CpC= 16
Temp = 25.5`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 51 T2= 0 T3= 2 CpC= 16
Temp = 25.6`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 51 T2= 0 T3= 1 CpC= 16
Temp = 25.7`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 16 CpC= 16
Temp = 25.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 15 CpC= 16
Temp = 25.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 15 CpC= 16
Temp = 25.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 14 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 13 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 14 CpC= 16
Temp = 25.9`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 15 CpC= 16
Temp = 25.8`C
50 100 150 200 250 300 350 400 450 500 550 600 650 T1= 52 T2= 0 T3= 16 CpC= 16

Posted: 05:08am 30 May 2026 Copy link to clipboard	TassyJim Guru

Thanks to Googles AI,I found another datasheet that suggests that the DS18S20 uses the same die as the DS1820 so has the same markings "DS1820"

That's bloody helpful!

I never trust the BS that Googles AI spits out but it might be right this time.

Jim

Posted: 05:19am 30 May 2026 Copy link to clipboard	Peter63 Senior Member

Feels like it would be so Dallas Maxim, the variant is also TO-92 which I have.

/Peter63

Posted: 05:27am 30 May 2026 Copy link to clipboard	phil99 Guru

Ok your data looks good.
Ideally when T1 is an even number the Temp. should be above xx.7 and below xy.3 and when T1 is an odd number the Temp. should be between xx.3 and xx.7, and that appears to be what you are getting.

So I think you now have a working Function that can cater for both DS18S20 and DS1820.
Edited 2026-05-30 15:30 by phil99

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