LM71 reads garbage sometimes.
Hello.
I'm facing a strong problem with LM71. Sometimes it reads garbage. Changed IC, changed PIC, changed power supply - same problem. If I cycle power sometimes one time, sometimes 3 times, etc. it then works. The code is as follows:
tried to play with pause times - no difference.Code:READTEMP: 'READ TEMPERATURE low thcs pause 5 shiftin thdta,thclk,msbpre,[result\16] pause 5 high thcs THC=result>>2/28 THC=THC-3 RETURN
What I'm doing wrong?
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Re: LM71 reads garbage sometimes.
Totally off the top of my head, are the variables the proper size for that math?
Robert
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Re: LM71 reads garbage sometimes.
THC and result variables are WORD type.
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Re: LM71 reads garbage sometimes.
Do you have the pins on the 71 pulled high?
Dave
Always wear safety glasses while programming.
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Re: LM71 reads garbage sometimes.
No, I should?
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Re: LM71 reads garbage sometimes.
Tried 4.7k pull-ups on all pins, does not helps.
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Re: LM71 reads garbage sometimes.
From cs low to the out of data the maximum time delay is 70 ns. you are using 5 ms. play with that delay using pauseus.
See data sheet timing table.
Cheers
Al.
All progress began with an idea
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Re: LM71 reads garbage sometimes.
Maybe enable Power up timer in the configsOriginally Posted by CuriousOne
If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
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Re: LM71 reads garbage sometimes.
Delay changes nothing, since I tried different values of PAUSE. The problem is startup, if once started OK, then it works OK. Also, I've tried to initialize it later, say after 5 seconds after power on - no luck.
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Re: LM71 reads garbage sometimes.
Pause has nothing to do with power up , sometimes mcu does not get nice crisp power on and it doesn't like slow lazy power on like when capacitors are on it's input, power up delay holds in reset until voltage is up to snuff and then allows it to boot.
One other thought : you have changed everything except the breadboard, breadboards do go bad.
Last edited by Archangel; - 1st February 2014 at 07:46.
If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
.
Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
.
There simply is no "Happy Spam" If you do it you will disappear from this forum.
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Re: LM71 reads garbage sometimes.
Well, I'm not using breadboard at all. I've tried to make different PCBs, switched power supplies, etc. no help.
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Re: LM71 reads garbage sometimes.
You will need to post your whole code , but here are a couple clues... The device needs a write on the rising edge, then data will be available on the falling edge. While CS is held low, send a command with a PRE then receive data with a POST. Also, are you sure you get valid data ever? The datasheet looks like you should be using LSB first, not MSB.
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