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Forum Index : Microcontroller and PC projects : Problem: Maximite and 1-wire
| Author | Message | ||||
| f.master Newbie  Joined: 11/07/2013 Location: GermanyPosts: 4 |
I am learning to use the 1-wire interface of the maximite. Hardware: B/W Maximite with firmware 4.4B mono One sensor connected to pin 19 1. the presence flag is not usable. It always shows "present" wether there is a sensor connected or not. 2. The CRC function description is wrong or the function itself is faulty. Example 1 runs and gives the expected result (CRC=0) The CRC8 is calculated from array variables. ' Evaluate 1-wire DS18B20 Temperature sensor ' Cls S1=19 'pin number Skip=&HCC 'code skip address Convert=&H44 'code start conversion RScratch=&HBE 'code read scratch registers Dim C(9) 'data array for CRC calculation ' OWWrite S1,1,2,Skip,Convert Pause 800 ' OWWrite S1,1,2,Skip,RScratch OWRead S1,2,9,A1,A2,A3,A4,A5,A6,A7,A8,A9 ' Negative = 0 If (A2 And &H80) Then Negative = 128 T1=((A1 And &H0F)*0.0625)+((A1 And &HF0)/16)+((A2 And &H07)*16)-Negative Print "Degrees C = ";T1 ' ' Calculate CRC ' C(0)=A1 C(1)=A2 C(2)=A3 C(3)=A4 C(4)=A5 C(5)=A6 C(6)=A7 C(7)=A8 C(8)=A9 Check=OWCRC8(9,C(0)) ' Print "CRC = ";Check ' End Example 2 will result in a reseted Maximite, runtime firmware crashed. The CRC8 is calculated from descrete variables. According the manual this is also a way to go. ' Evaluate 1-wire DS18B20 Temperature sensor ' Cls S1=19 'pin number Skip=&HCC 'code skip address Convert=&H44 'code start conversion RScratch=&HBE 'code read scratch registers ' OWWrite S1,1,2,Skip,Convert Pause 800 ' OWWrite S1,1,2,Skip,RScratch OWRead S1,2,9,A1,A2,A3,A4,A5,A6,A7,A8,A9 ' Negative = 0 If (A2 And &H80) Then Negative = 128 T1=((A1 And &H0F)*0.0625)+((A1 And &HF0)/16)+((A2 And &H07)*16)-Negative Print "Degrees C: ";T1 ' ' Calculate CRC ' Check=OWCRC8(9,A1,A2,A3,A4,A5,A6,A7,A8,A9) Print "CRC: ";Check ' End Additional info: I tried also older Basic versions: V3.1 -> crash V3.2C -> Error: Expecting closing bracket (at line Check=OWCRC8(..) V4.1 -> Error: Expecting closing bracket (at line Check=OWCRC8(..) V4.3mono -> Invalid syntax (at line Check=OWCRC8(..) V4.4B mono -> crash The presence flag is not useable in all the versions. f.master |
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| f.master Newbie Joined: 11/07/2013 Location: GermanyPosts: 4 |
It seems, the Maximite is phased out already. Lets look out for something else then. f.master |
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| JohnS Guru  Joined: 18/11/2011 Location: United KingdomPosts: 3816 |
I guess you didn't notice how very busy things have been (I cannot imagine how you cannot know!) and yours was just one post that I guess Geoff missed. Did you try emailing him or a PM? I have no way to test your samples so for all I know they are bad syntax. Maybe someone else can... John |
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| f.master Newbie Joined: 11/07/2013 Location: GermanyPosts: 4 |
I noticed this. I am busy too. My second post was more a reminder then a complaint. Should set a Smily there. No. I used just this communication channel. Because Geoff is very busy I avoided to place nore than one message. Everybody with the right equipment can test this. A sensor is not required, the port can be left open. The result is always the same. With an open port, the presence flag should show "not present', but it shows "present". It would be nice if the presence flag could be fixed because it is an important item in this system. The bug in the CRC function is may be not a bug. Just the manual has to be corrected in that way, only Array Vars are allowed. f.master |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6102 |
I don't have a to test with but running the code without any sensor gave the expected results. Do you have the pullup resistor connected? Without it the result will be '1' without any sensor. With the pullup, the result for Presence and MM.OW is '0' The presence variable is only valid after a RESET. The MM.OW is valid after most OW commands. I added a couple of PRINT statements: ' Evaluate 1-wire DS18B20 Temperature sensor
' Cls S1=12 'pin number Skip=&HCC 'code skip address Convert=&H44 'code start conversion RScratch=&HBE 'code read scratch registers Dim C(9) 'data array for CRC calculation ' owreset s1, p print "Presence = ";p OWWrite S1,1,2,Skip,Convert print "MM.OW = ";MM.OW Pause 800 ' OWWrite S1,1,2,Skip,RScratch OWRead S1,2,9,A1,A2,A3,A4,A5,A6,A7,A8,A9 print "MM.OW = ";MM.OW ' Negative = 0 If (A2 And &H80) Then Negative = 128 T1=((A1 And &H0F)*0.0625)+((A1 And &HF0)/16)+((A2 And &H07)*16)-Negative Print "Degrees C = ";T1 ' ' Calculate CRC ' C(0)=A1 C(1)=A2 C(2)=A3 C(3)=A4 C(4)=A5 C(5)=A6 C(6)=A7 C(7)=A8 C(8)=A9 Check=OWCRC8(9,C(0)) ' Print "CRC = ";Check ' End The results I get without a sensor are: Presence = 0
MM.OW = 0 MM.OW = 0 Degrees C = -0.0625 CRC = 99 I agree that the is a problem with the CRC code. It works with arrays and string variables but not a set of numeric variables. Jim VK7JH MMedit MMBasic Help |
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| f.master Newbie Joined: 11/07/2013 Location: GermanyPosts: 4 |
Thats it. In my prototyp curcuit the pullup resistor is located near the sensor. Cutting the line to test the presence flag also removed the pullup and gave this result. Shame on me, not had seen this. The pullup has to be placed near the Maximite port, before the first cable connection going to the outside world. Thanks for the hint. f.master |
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