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Forum Index : Microcontroller and PC projects : CMM2: DS18B20 Temp sensor problem
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| robert.rozee Guru  Joined: 31/12/2012 Location: New ZealandPosts: 2396 |
from the above link: "If the ROM does not follow the pattern 28-xx-xx-xx-xx-00-00-xx then the DS18B20 sensor is a clone [5]." and "References 5. Own investigations 2019, unpublished." the only statement about the content of the ROM made by the DS18B20 datasheet is: "The least significant 8 bits of the ROM code contain the DS18B20’s 1-Wire family code: 28h. The next 48 bits contain a unique serial number. The most significant 8 bits contain a cyclic redundancy check (CRC) byte that is calculated from the first 56 bits of the ROM code." based upon the DS18B20 datasheet, and without further input directly from Maxim, i'd find it hard to accept as gospel the "00 00" assertion; Maxim and/or DS could have in the past released any (large or small) number of DS18B20 with non-zero values in the 6th and 7th byte of the ROM. i also have doubts about the forensic usefulness of the default contents of EEPROM - these values could innocently be changed by Maxim during manufacture and testing, during sample testing post-manufacturing, or by anyone in the supply chain who may have wished to test devices they handled. Maxim may have a number of plants capable of manufacturing DS18B20, and different plants could use their own individual testing and calibration routines that leave the EEPROM contents in set to a pattern identified as 'fake' . apart from abnormal behaviour (including inaccuracy), the only sure way to identify a non-maxim part is to split the case open and examine the silicon die. cheers, rob :-) Edited 2020-08-09 21:47 by robert.rozee |
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2943 |
Hi Rob, All, I have been wondering about the ROM as surely if you go to the effort to create a ‘clone’ could you not just clone the ROM code. IF the one I bought from Jaycar is a fake it seems to have an almost identical temperature report to the genuine one.. (see my previous post with the two chips tied together.) What is the zero degrees issue? I can test them in a fridge/freezer/ice if you like. Regards, Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3297 |
Paul_L once suggested to me that a very good way of testing/comparing perhaps dodgy waterproof DS18B20s was to put crushed ice in a glass, pour in a modest amount of chilled water, wait a few minutes for the ice to bring the water to very close to freezing, and insert the probes. That should be very close to 0C if you have the mix right, and a well-established universal calibration point. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6210 |
Rob, you left out the bit about conversion times While I agree that the rom code 'could' be valid, it is unlikely in the extreme that Maxim will have produced a batch of chips that do the conversions in half the time, and then gone back to the normal time in subsequent batches. I suspect that the clone manufacturers chose rom codes well outside the expected range to prevent the chance of duplicate codes being discovered in the immediate future. The chips that Mick and I purchased from the Jaycar supply chain, all have slower timing than the usual times seen with known good chips, but the timing is still within published specs so 'could' be valid, but suspicious. I buy through Ebay. I expect clones, recycled chips, out-of-spec rejects... Jim VK7JH MMedit |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2943 |
Hi Jim, All, I did the ice water trick and both sensors reported the same readings within 0.25C all the way down from the ambient of 19.5C down to where they stopped updating at 0.5C Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 Mouser = 0.5 Jaycar = 0.5 The Jaycar unit seems to respond quicker to the change but only by the 0.25C then the Mouser unit caught up and they were together again until the Jaycar once again responded to drop before the Mouser one As far as I can tell the 2 sensors as are accurate as each other. It took a good 10 minutes for both units to settle at 0.5C Kind Regards Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
Funny thing about standards -- most of them aren't standardized -- except for the ice point of water. It works best if you use distilled water (filtered rain water?), use an insulated coffee mug, ice chips not big ice cubes, stir the ice water for 30 seconds before inserting the probe, and insert the probe in the center of the mug without touching the sides or bottom. You should be able to achieve within 0.2°C of a true 0°C easily. Paul in NY |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2943 |
Hi Paul, I used filtered ice water from our fridge and ice dispenser... After about 15min neither sensor dropped below 0.5c I actually did another test that I didn’t report, I used a can of freeze spray and they once again followed each other within 0.5 and 0.25C (dropping was a bit more inconsistent (no more than 1.5C but I put that down to me spraying one more than the other chip, it is hard to equally spray each DS18B20 even though I bound them together)... At about -27.5C (a bit like a Polak summer??) I stopped and let them both recover and the spread between the known good Mouser and the suspect Jaycar chip was no more than 0.25 99% of the time with the odd one 0.5 difference between chips and quite often reading Exactly the same. My conclusion is that the Jaycar chip IF it is a fake is an extremely good fake and is most definitely suitable to be used as a DS18B20. Kind Regards, Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
I don't understand why you guys go chasing the cheapest questionable source for these sensors. You're probably buying sensors that didn't pass final inspection. I suspect that the production yield after final inspection is less than 30%! Bandgap sensors are difficult to make, requiring the calibration of the current density in two p-n diode junctions and measuring the difference between them. Why would you deliberately buy seconds when Mouser has over 3,000 of the real thing in stock at a price of < $4.00 each. The only difficult part is finding an appropriately sized closed end stainless steel or copper tube to insert the TO92 case into, or just mounting them by their wires on a little terminal board. Paul in NY |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2943 |
Hi Paul, The object is NOT to buy cheap it is to determine exactly what you will get for your money. It is very confusing, for instance this listing from Mouser. Mouser DS18B20 Includes 2 pages of offerings for DS18B20, 'Manufacturers' include many different sources. For example Seeed Studio Maxim Adafruit Sparkfun DFRobot ANAVI Technology DLP Design.. Then Mouser has a fairly expensive freight cost To AUS unless you spend $60 which I do when I buy from them. Mind you I really like Mouser I get my parts usually 3-4 days after I order which is fantastic coming from the `REAL' antipodes. Here in Aus we really are stuck with RS Components (great to deal with and free freight no matter order QTY), but often have to buy in bags of 5, 10 or more. Element14 which offers free freight over I think $50. Both the above are generally (not always) expensive prices and I have found recently that even though they say a qty is in stock, often they are placed on back order which could be 2-3 months away. Then there are Jaycar and Altronics who whilst cheaper have a very limited repertoire of stock but they are generally in range of almost everywhere, if you are in the cities. Then there is really only a smattering of other suppliers with the stuff we tinker around with and mostly do not stock much at all. Kind Regards Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2403 |
TassyJim's test program with some mods for the PicoMite. 'DS18x20 test code by TassyJim ' Input "Type Pin number ",PinNbr Input "Type PicoMite GPxx number for the DS18B20 (include the GP) "; GPPin$ Dim INTEGER PinNbr = MM.Info(pinno GPPin$) Print "Family name: ";FamilyName$(PinNbr) Print "Rom Code:   ";getRomCode$(PinNbr) Print "ScratchPad:  ";getScratchpad$(PinNbr) If powerMode(PinNbr) Then  Print "Power mode  External" Else  Print "Power mode  Parasitic" EndIf For n = 9 To 12  Print  x = setResolution(PinNbr, n)  Print "ScratchPad:  ";getScratchpad$(PinNbr)  Timer = 0  Print "Temperature: ";getTemp(PinNbr);" ";Timer;"mS,";n;" bit" Next n Print : Print "Tempr() without start", TEMPR(PinNbr) TEMPR START PinNbr,0 : Print "Tempr Start Pin,0", TEMPR(PinNbr) TEMPR START PinNbr,1 : Print "Tempr Start Pin,1", TEMPR(PinNbr) TEMPR START PinNbr,2 : Print "Tempr Start Pin,2", TEMPR(PinNbr) TEMPR START PinNbr,3 : Print "Tempr Start Pin,3", TEMPR(PinNbr) End Function getRomCode$(PinNbr As INTEGER) ' get ROM Code - useful if you want more than 1 device on wire Local INTEGER a1,a2,a3,a4,a5,a6,a7,a8 OneWire WRITE PinNbr,1,1,&h33 'read ROM code OneWire READ PinNbr,0,8,a1,a2,a3,a4,a5,a6,a7,a8 getRomCode$ = Hex$(a1,2)+" "+Hex$(a2,2)+" "+Hex$(a3,2)+" "+Hex$(a4,2)+" "+Hex$(a5,2)+" "+Hex$(a6,2)+" "+Hex$(a7,2)+" "+Hex$(a8 ,2) End Function Function getScratchpad$(PinNbr As INTEGER) 'ONEWIRE Write PinNbr,1,9,&h55,a1,a2,a3,a4,a5,a6,a7,a8  'read from scratchpad OneWire WRITE PinNbr,1,2,&hcc,&hbe OneWire READ PinNbr,0,8,a,b,c,d,e,f,g,h getScratchpad$ = Hex$(a,2)+" "+Hex$(b,2)+" "+Hex$(c,2)+" "+Hex$(d,2)+" "+Hex$(e,2)+" "+Hex$(f,2)+" "+Hex$(g,2)+" "+Hex$(h,2) End Function Function powerMode(PinNbr As INTEGER) As INTEGER ' check whether power external (1) or parasitic (0) OneWire RESET PinNbr OneWire WRITE PinNbr, 1,2,&hcc, &hb4 OneWire READ PinNbr,4,1,powerMode End Function Function getFamily(PinNbr As INTEGER) As INTEGER getFamily = Val("&h"+Left$(getRomCode$(PinNbr),2)) End Function Function FamilyName$(PinNbr As INTEGER) Local INTEGER fn fn = getFamily(PinNbr) Select Case fn  Case 16   FamilyName$ = "DS1820/DS18S20"  Case 34   FamilyName$ = "DS18S22"  Case 40   FamilyName$ = "DS18B20"  Case Else   FamilyName$ = "Unknown" End Select End Function Function setResolution(PinNbr As INTEGER,r As INTEGER) r = r-9 If r < 0 Then r = 0 If r > 3 Then r = 3 r = r*32+31 OneWire WRITE PinNbr, 1,5,&hcc, &h4E, &hFF,&hFF,r End Function Function getTemp(PinNbr As INTEGER) As FLOAT Local INTEGER fn, t, T1, T2, a,b,c,d,e,f,g,h Local FLOAT Value fn = getFamily(PinNbr) power = powerMode(PinNbr) OneWire RESET PinNbr             ' reset before command OneWire WRITE PinNbr, 8, 2, &hcc, &h44    ' start conversion 'read external when b goes high, for parasitic just wait If power = 0 Then  Pause 750 Else  t = Timer  Do   If Timer - t > 1000 Then    Value = 1000    Exit Do   EndIf   OneWire READ PinNbr, 4 , 1 , b       ' conversion done?  Loop Until b = 1 EndIf If Value = 0 Then ' we have not timed out yet  OneWire WRITE PinNbr, 1, 2, &hcc, &hbe    ' command read data  OneWire READ PinNbr, 2, 2, T1, T2      ' get the data  OneWire RESET PinNbr  Select Case fn   Case 16 'DS18S20 or DS1820    OneWire WRITE PinNbr,1,2,&hcc,&hbe    OneWire READ PinNbr,0,8,a,b,c,d,e,f,g,h    If T2 And &h80 Then    'if MSB of T2=1 then negative     'Read 12bit resolution and adjust     'truncate 0.5deg value (or use integer division \)     T1 = T1 And &hFE     T1=T1 / 2          'make whole degrees     'add compensation values read from scratchpad     T1=T1*16          'make lsb 1/16 degree     T1 = T1 -4 +(16 - g)   'add 12 bit value     'take 2s complement     T1 = (T1 Xor &hFF) + 1     Value = -T1/16         'make decimal value in degrees    Else                'positive temp     Value = T1 / 2         '9bit value     'Read 12bit resolution and adjust     T1 = T1 And &hFE    'truncate 0.5deg(or use integer division \)     Value = T1/2- 0.25 + (16 - g) /16  '12 bit value    EndIf   Case 34, 40 ' DS18S22 or DS18B20    If T2 And &b1000 Then    'negative temp     'make 2s complement (1s complement+1)     T2 = (T2 Xor &hFF)     T1 = (T1 Xor &hFF)+1     If T1=1 Then T2=T2+1     'add the carry if required     Value = -((T2 And &b111) * 256 + T1) / 16    Else               'positive temp     Value = ((T2 And &b111) * 256 + T1) / 16    EndIf   Case Else    Value = 1000  End Select EndIf getTemp= Value End Function And the output with my non-genuine units. > RUN Type PicoMite GPxx gp6 Family name: Unknown Rom Code:   29 61 64 12 3D D4 A4 B8 ScratchPad:  7B 01 FF FF 7B FF FF FF Power mode  External ScratchPad:  FF FF FF FF FF FF FF FF Temperature:  1000  17.838mS, 9 bit ScratchPad:  FF FF FF FF FF FF FF FF Temperature:  1000  17.851mS, 10 bit ScratchPad:  BD 80 FF FF AF FF FF FF Temperature:  1000  17.827mS, 11 bit ScratchPad:  7B 01 FF FF 7F FF FF FF Temperature:  1000  17.815mS, 12 bit Tempr() without start   23.625 Tempr Start Pin,0     23.625 Tempr Start Pin,1     23.625 Tempr Start Pin,2     23.375 Tempr Start Pin,3     23.375 > RUN Type PicoMite GPxx gp7 Family name: DS18B20 Rom Code:   28 3F 44 57 04 E1 3C 4D ScratchPad:  80 01 00 00 7F A5 A5 66 Power mode  External ScratchPad:  80 01 FF FF 1F A5 A5 66 Temperature:  22.5  495.694mS, 9 bit ScratchPad:  68 01 FF FF 3F A5 A5 66 Temperature:  22.75  495.831mS, 10 bit ScratchPad:  6C 01 FF FF 5F A5 A5 66 Temperature:  22.75  495.681mS, 11 bit ScratchPad:  6C 01 FF FF 7F A5 A5 66 Temperature:  22.8125  495.811mS, 12 bit Tempr() without start   1000 Tempr Start Pin,0     1000 Tempr Start Pin,1     22.75 Tempr Start Pin,2     1000 Tempr Start Pin,3     22.8125 > Edited 2025-03-10 10:50 by phil99 |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6210 |
Found time to test before leaving. local retailer (Jaycar) Family name: DS18B20 Rom Code: 28 AA 42 A3 41 14 01 D5 ScratchPad: 51 01 00 00 7F FF 60 10 Power mode External ScratchPad: 51 01 FF FF 1F FF 1F 10 Temperature: 21 109.795mS, 9 bit ScratchPad: 50 01 FF FF 3F FF 3F 10 Temperature: 21 199.835mS, 10 bit ScratchPad: 50 01 FF FF 5F FF 5F 10 Temperature: 20.875 379.825mS, 11 bit ScratchPad: 4E 01 FF FF 7F FF 7F 10 Temperature: 21 739.858mS, 12 bit Tempr() without start 21 210.887 Tempr Start Pin,0 21 110.06 Tempr Start Pin,1 21 209.799 Tempr Start Pin,2 21 409.839 Tempr Start Pin,3 21 809.776 > RUN Known good. Family name: DS18B20 Rom Code: 28 62 D8 F1 05 00 00 18 ScratchPad: 50 05 4B 46 7F FF 0C 10 Power mode External ScratchPad: 50 05 FF FF 1F FF 0C 10 Temperature: 22 94.519mS, 9 bit ScratchPad: 60 01 FF FF 3F FF 10 10 Temperature: 21.75 169.149mS, 10 bit ScratchPad: 5C 01 FF FF 5F FF 04 10 Temperature: 21.75 318.568mS, 11 bit ScratchPad: 5C 01 FF FF 7F FF 04 10 Temperature: 21.625 617.607mS, 12 bit Tempr() without start 21.75 210.933 Tempr Start Pin,0 22 109.848 Tempr Start Pin,1 21.75 209.812 Tempr Start Pin,2 21.75 409.785 Tempr Start Pin,3 21.625 809.801 The module purchased form Jaycar 5 years ago is slower that the specs but still just fast enough for the picomite code. It may give errors in 9 and 10 bit resolution. Jim VK7JH MMedit |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2403 |
More playing with Jim's program. Added some comments to help add unknown / non-genuine devices. 'DS18x20 test code by TassyJim ' Input "Type Pin number ",PinNbr Input "Type PicoMite GPxx number for the DS18B20 (include the GP) "; GPPin$ Dim INTEGER PinNbr = MM.Info(pinno GPPin$) Print "Family name: ";FamilyName$(PinNbr) Print "Rom Code:   ";getRomCode$(PinNbr) Print "ScratchPad:  ";getScratchpad$(PinNbr) If powerMode(PinNbr) Then  Print "Power mode  External" Else  Print "Power mode  Parasitic" EndIf For n = 9 To 12  Print  x = setResolution(PinNbr, n)  Print "ScratchPad:  ";getScratchpad$(PinNbr)  Timer = 0  Print "Temperature: ";getTemp(PinNbr);"`C  ";Timer;"mS,";n;" bit" Next n Print :t=Timer : Print "Tempr() without Start", TEMPR(PinNbr);" `C",Timer-t;" mS" TEMPR START PinNbr,0 :t=Timer :ds18=TEMPR(PinNbr):t=Timer-t : Print "Tempr Start pin,0", ds18, t TEMPR START PinNbr,1 :t=Timer :ds18=TEMPR(PinNbr):t=Timer-t : Print "Tempr Start pin,1", ds18, t TEMPR START PinNbr,2 :t=Timer :ds18=TEMPR(PinNbr):t=Timer-t : Print "Tempr Start pin,2", ds18, t TEMPR START PinNbr,3 :t=Timer :ds18=TEMPR(PinNbr):t=Timer-t : Print "Tempr Start pin,3", ds18, t Print "*** The first RomCode value (a1) can be used to add extra devices to the FamilyName & getTemp functions" Print "look for *** comments in those functions" End Function getRomCode$(PinNbr As INTEGER) ' get ROM Code - useful if you want more than 1 device on wire '*** The first value returned (a1) can be used to add extra devices to the FamilyName & getTemp functions 'look for *** comments in those functions Local INTEGER a1,a2,a3,a4,a5,a6,a7,a8 OneWire WRITE PinNbr,1,1,&h33 'read ROM code OneWire READ PinNbr,0,8,a1,a2,a3,a4,a5,a6,a7,a8 getRomCode$ = Hex$(a1,2)+" "+Hex$(a2,2)+" "+Hex$(a3,2)+" "+Hex$(a4,2)+" "+Hex$(a5,2)+" "+Hex$(a6,2)+" "+Hex$(a7,2)+" "+Hex$(a8 ,2) End Function Function getScratchpad$(PinNbr As INTEGER) 'ONEWIRE Write PinNbr,1,9,&h55,a1,a2,a3,a4,a5,a6,a7,a8  'read from scratchpad OneWire WRITE PinNbr,1,2,&hcc,&hbe OneWire READ PinNbr,0,8,a,b,c,d,e,f,g,h getScratchpad$ = Hex$(a,2)+" "+Hex$(b,2)+" "+Hex$(c,2)+" "+Hex$(d,2)+" "+Hex$(e,2)+" "+Hex$(f,2)+" "+Hex$(g,2)+" "+Hex$(h,2) End Function Function powerMode(PinNbr As INTEGER) As INTEGER ' check whether power external (1) or parasitic (0) OneWire RESET PinNbr OneWire WRITE PinNbr, 1,2,&hcc, &hb4 OneWire READ PinNbr,4,1,powerMode End Function Function getFamily(PinNbr As INTEGER) As INTEGER getFamily = Val("&h"+Left$(getRomCode$(PinNbr),2)) End Function Function FamilyName$(PinNbr As INTEGER) Local INTEGER fn fn = getFamily(PinNbr) Select Case fn  Case 16  '&H10   FamilyName$ = "DS1820/DS18S20"  Case 34  '&H22   FamilyName$ = "DS18S22"  Case 40  '&H28   FamilyName$ = "DS18B20"  Case 41  '&H29   FamilyName$ = "a non-genuine DS18B20"  '*** Add extra cases here using the first value returned by Function getRomCode  Case Else   FamilyName$ = "Unknown" End Select End Function Function setResolution(PinNbr As INTEGER,r As INTEGER) r = r-9 If r < 0 Then r = 0 If r > 3 Then r = 3 r = r*32+31 OneWire WRITE PinNbr, 1,5,&hcc, &h4E, &hFF,&hFF,r End Function Function getTemp(PinNbr As INTEGER) As FLOAT Local INTEGER fn, t, T1, T2, a,b,c,d,e,f,g,h Local FLOAT Value fn = getFamily(PinNbr) power = powerMode(PinNbr) OneWire RESET PinNbr             ' reset before command OneWire WRITE PinNbr, 8, 2, &hcc, &h44    ' start conversion 'read external when b goes high, for parasitic just wait If power = 0 Then  Pause 750 Else  t = Timer  Do   If Timer - t > 1000 Then    Value = 1000    Print "*** Timeout ***"    Exit Do   EndIf   OneWire READ PinNbr, 4 , 1 , b       ' conversion done?  Loop Until b = 1 '  Print Timer-t;" mS conversion time", EndIf If Value = 0 Then ' we have not timed out yet  OneWire WRITE PinNbr, 1, 2, &hcc, &hbe    ' command read data  OneWire READ PinNbr, 2, 2, T1, T2      ' get the data  OneWire RESET PinNbr  Select Case fn   Case 16 'DS18S20 or DS1820    OneWire WRITE PinNbr,1,2,&hcc,&hbe    OneWire READ PinNbr,0,8,a,b,c,d,e,f,g,h    If T2 And &h80 Then    'if MSB of T2=1 then negative     'Read 12bit resolution and adjust     'truncate 0.5deg value (or use integer division \)     T1 = T1 And &hFE     T1=T1 / 2          'make whole degrees     'add compensation values read from scratchpad     T1=T1*16          'make lsb 1/16 degree     T1 = T1 -4 +(16 - g)   'add 12 bit value     'take 2s complement     T1 = (T1 Xor &hFF) + 1     Value = -T1/16         'make decimal value in degrees    Else                'positive temp     Value = T1 / 2         '9bit value     'Read 12bit resolution and adjust     T1 = T1 And &hFE    'truncate 0.5deg(or use integer division \)     Value = T1/2- 0.25 + (16 - g) /16  '12 bit value    EndIf   Case 34, 40 ' DS18S22 or DS18B20    If T2 And &b1000 Then    'negative temp     'make 2s complement (1s complement+1)     T2 = (T2 Xor &hFF)     T1 = (T1 Xor &hFF)+1     If T1=1 Then T2=T2+1     'add the carry if required     Value = -((T2 And &b111) * 256 + T1) / 16    Else               'positive temp     Value = ((T2 And &b111) * 256 + T1) / 16    EndIf   Case 41 '&H29, a non genuine DS18B20    If T2 And &b1000 Then    'negative temp     'make 2s complement (1s complement+1)     T2 = (T2 Xor &hFF)     T1 = (T1 Xor &hFF)+1     If T1=1 Then T2=T2+1     'add the carry if required     Value = -((T2 And &b111) * 256 + T1) / 16    Else               'positive temp     Value = ((T2 And &b111) * 256 + T1) / 16    EndIf   '*** Add extra cases here using the first value returned by Function getRomCode   Case Else 'Unknown device     ' *** use the output of this to create the scale factor of the unknown device    'Value = 1000    If T2 And &b1000 Then    'negative temp     'make 2s complement (1s complement+1)     T2 = (T2 Xor &hFF)     T1 = (T1 Xor &hFF)+1     If T1=1 Then T2=T2+1     'add the carry if required     Value = -((T2 And &b111) * 256 + T1) / 1'<-This is where you put the scale factor    Else               'positive temp     Value = ((T2 And &b111) * 256 + T1) / 1'<-This is where you put the scale factor    EndIf  End Select EndIf getTemp= Value End Function Example output. This one always reads 85° until after a Tempr Start pin,2 or 3 command then is ok till next power cycle. > RUN Type PicoMite GPxx number for the DS18B20 (include the GP) ? gp6 Family name: a non-genuine DS18B20 Rom Code:   29 61 64 12 3D D4 A4 B8 ScratchPad:  51 05 FF FF 7F FF FF FF Power mode  External ScratchPad:  FF FF FF FF FF FF FF FF Temperature:  85.0625`C  17.934mS, 9 bit ScratchPad:  FF FF FF FF FF FF FF FF Temperature:  85.0625`C  17.951mS, 10 bit ScratchPad:  A8 82 FF FF AF FF FF FF Temperature:  680`C  17.91mS, 11 bit ScratchPad:  51 05 FF FF 7F FF FF FF Temperature:  85.0625`C  17.935mS, 12 bit Tempr() without Start   85 `C  210.435 mS Tempr Start pin,0     85    103.408 Tempr Start pin,1     85    203.84 Tempr Start pin,2     27.875  403.835 Tempr Start pin,3     27.875  803.819 *** The first RomCode value (a1) can be used to add extra devices to the FamilyName & getTemp functions look for *** comments in those functions > RUN Type PicoMite GPxx number for the DS18B20 (include the GP) ? gp6 Family name: a non-genuine DS18B20 Rom Code:   29 61 64 12 3D D4 A4 B8 ScratchPad:  BF 01 FF FF 7B FF FF FF Power mode  External ScratchPad:  FF FF FF FF FF FF FF FF Temperature:  27.9375`C  17.964mS, 9 bit ScratchPad:  FF FF FF FF FF FF FF FF Temperature:  27.9375`C  17.942mS, 10 bit ScratchPad:  DF 80 FF FF AF FF FF FF Temperature:  223`C  17.93mS, 11 bit ScratchPad:  BF 01 FF FF 7F FF FF FF Temperature:  27.9375`C  17.942mS, 12 bit Tempr() without Start   27.875 `C    210.452 mS Tempr Start pin,0     27.875  104.167 Tempr Start pin,1     27.875  203.82 Tempr Start pin,2     27.6875     403.821 Tempr Start pin,3     27.6875     803.819 *** The first RomCode value (a1) can be used to add extra devices to the FamilyName & getTemp functions look for *** comments in those functions Edit. Prompted by Volhout's mention of the RP2350 pin issue I reduced the pullup resistor from 10k to 1.2k. Now the Rom Code value of a1 is &H28, as it should be. Was &H29. It no longer reads 85°C in Jim's program but still requires an initial Tempr Start to get Tempr() to read correctly. Edited 2025-03-10 20:08 by phil99 |
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| dddns Senior Member  Joined: 20/09/2024 Location: GermanyPosts: 212 |
Very helpful, many thanks for sharing! Will try later on |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2403 |
For anyone with a DS18x20 device that doesn't work with Tempr() but does give sensible results with Jim's test program here is a Function derived from Jim's program. Usage:- Print DS18x20(pin); "`C" Or Temp = DS18x20(mm.info(pinno GPxx)) : Print Temp; "`C" There are some comments to help adapt it to your device. Function DS18x20(PinNbr As INTEGER) As FLOAT ' Extracted from DS18x20 test code by TassyJim ' Run that program and find the values that get your device to work. ' Copy those values into this Function Local INTEGER t, T1, T2, done Local FLOAT Value=0 OneWire RESET PinNbr ' reset before command OneWire WRITE PinNbr, 8, 2, &hcc, &h44 ' start conversion t = Timer Do 'There should be a result in less than 1000mS If Timer - t > 1000 Then Value = 1000 'standard error code Print "*** Timeout ***", Exit Do EndIf OneWire READ PinNbr, 4 , 1 , done ' conversion done? Loop Until done ' Print Timer - t;" mS conversion time", 'un-comment this to see how long it took If Value = 0 Then ' we have not timed out yet, so assume data is valid OneWire WRITE PinNbr, 1, 2, &hcc, &hbe ' command read data OneWire READ PinNbr, 2, 2, T1, T2 ' get the data OneWire RESET PinNbr If T2 And &b1000 Then 'negative temp 'make 2s complement (1s complement+1) T2 = (T2 Xor &hFF) T1 = (T1 Xor &hFF)+1 If T1=1 Then T2=T2+1 'add the carry if required Value = -((T2 And &b111) * 256 + T1) / 16 'adjust this if the temp. is wrong Else 'positive temp Value = ((T2 And &b111) * 256 + T1) / 16 'adjust this if the temp. is wrong EndIf EndIf DS18x20 = Value End Function |
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| dddns Senior Member Joined: 20/09/2024 Location: GermanyPosts: 212 |
Many thanks, I appreciate that! I found, that my sensor is reliably answering after 600ms for 9 and 10 bit. Knowing that, I code regarding it. Your function does not deliver earlier I guess. So the best would be, that tempr() would have parameters to overwrite the datasheet defaults. Anyway, tempr() is not usable at all for me only tempr start. So if I would really want to have the reading right now, maybe this function comes into play.In any case it's good to know how it is done and you gave the shortcut..thanks! |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2403 |
If you post the results of TassyJim's test program here I may be able to adapt the Function to your unit. As it is now the Function simply waits as long as necessary to get a reading (up to 1S). However if the 'x' in DS18x20 isn't 'B' or 'S' some changes may need to be made. |
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| dddns Senior Member Joined: 20/09/2024 Location: GermanyPosts: 212 |
First breakfast :) Does it make a difference to? tempr start(xx):pause xx:? tempr(xx) |
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| dddns Senior Member Joined: 20/09/2024 Location: GermanyPosts: 212 |
your function works very nice: > RUN 473.178 mS conversion time 22.4375`C 473.595 mS conversion time 22.4375`C 473.79 mS conversion time 22.4375`C 473.998 mS conversion time 22.4375`C 473.204 mS conversion time 22.4375`C 473.388 mS conversion time 22.4375`C 473.607 mS conversion time 22.4375`C 473.853 mS conversion time 22.4375`C 474.02 mS conversion time 22.4375`C 473.178 mS conversion time 22.5`C 474.091 mS conversion time 22.5`C > |
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| dddns Senior Member Joined: 20/09/2024 Location: GermanyPosts: 212 |
My 600ms I have lived with could be tuned a bit :) Type PicoMite GPxx number for the DS18B20 (include the GP) ? gp15 Family name: DS18B20 Rom Code: 28 E9 CA 43 D4 E1 3C 7D ScratchPad: 68 01 55 05 7F A5 A5 66 Power mode External ScratchPad: 68 01 FF FF 1F A5 A5 66 Temperature: 22`C 493.538mS, 9 bit ScratchPad: 60 01 FF FF 3F A5 A5 66 Temperature: 22.25`C 493.751mS, 10 bit ScratchPad: 64 01 FF FF 5F A5 A5 66 Temperature: 22.375`C 493.908mS, 11 bit ScratchPad: 66 01 FF FF 7F A5 A5 66 Temperature: 22.4375`C 493.918mS, 12 bit Tempr() without Start 1000 `C 209.257 mS Tempr Start pin,0 1000 99.321 Tempr Start pin,1 22.25 204.063 Tempr Start pin,2 1000 399.376 Tempr Start pin,3 22.4375 803.979 *** The first RomCode value (a1) can be used to add extra devices to the FamilyName & getTemp functions look for *** comments in those functions > |
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| dddns Senior Member Joined: 20/09/2024 Location: GermanyPosts: 212 |
> do:tempr start gp15,1:pause 474:? tempr(gp15):loop 22.25 22.25 22.25 22.25 22.25 22.25 22.25 22.25 22.25 > > do:tempr start gp15,1:pause 472:? tempr(gp15):loop 1000 1000 1000 1000 1000 1000 1000 > |
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