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Author Topic: Pic24fj128gb206 ADC pin staying at logic high  (Read 1311 times)

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Offline muthukural001Topic starter

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Pic24fj128gb206 ADC pin staying at logic high
« on: February 16, 2018, 05:54:36 pm »
Hello All,
Till yesterday, I was able to measure thermistor over PIC24 ADC's AN2(RB2) pin. Today, I had read Thermistor and surprisingly I got ADC input voltage which is very near to full-scale voltage of 3.3V but the Thermistor is giving 1.6V only .  Hence I disconnected the Thermistor from ADC pin and check, ADC pin was showing 3.3V. Even after I switched on and off,it was showing 3.3V in the Thermistor not connected State. please suggest..

Regards,
Muthu
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Offline Gibson486

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Re: Pic24fj128gb206 ADC pin staying at logic high
« Reply #1 on: February 16, 2018, 06:29:53 pm »
It could be anything....from you changing your code, to esd damaging a pin, to an accidental short...I mean, the possibilities are endless.
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Offline NorthGuy

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Re: Pic24fj128gb206 ADC pin staying at logic high
« Reply #2 on: February 17, 2018, 01:48:44 am »
Most likely you have configured it as a digital output, possibly when you were trying to configure other pins or PPS.
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Offline muthukural001Topic starter

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Re: Pic24fj128gb206 ADC pin staying at logic high
« Reply #3 on: February 17, 2018, 06:00:09 am »
No it is the same program which was working fine previously. I don't know where to debug ......
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Offline Buriedcode

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Re: Pic24fj128gb206 ADC pin staying at logic high
« Reply #4 on: February 17, 2018, 03:41:55 pm »
You should check for a blown IO pin.  Check for low resistance between the pin and VDD - also as each IO has diode protection you should see ~0.65V between IO and VDD, and GND and IO (anode to cathode)
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Offline NorthGuy

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Re: Pic24fj128gb206 ADC pin staying at logic high
« Reply #5 on: February 17, 2018, 07:10:14 pm »
Quote from: muthukural001 on February 17, 2018, 06:00:09 am
No it is the same program which was working fine previously. I don't know where to debug ......

Try anorther chip. This way you will see if this is a chip malfunction or your program.
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Offline Kalvin

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Re: Pic24fj128gb206 ADC pin staying at logic high
« Reply #6 on: February 17, 2018, 07:13:17 pm »
Or, use another I/O-pin if you don't have another chip yet.
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Offline muthukural001Topic starter

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Re: Pic24fj128gb206 ADC pin staying at logic high
« Reply #7 on: February 22, 2018, 10:51:49 am »
Sorry for delay.Yaah  It was working when I shifted ADC function to another ADC pin.It looks like I damaged the pin..





Regards,
Muthu
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Online SiliconWizard

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Re: Pic24fj128gb206 ADC pin staying at logic high
« Reply #8 on: February 22, 2018, 03:38:49 pm »
Either the pin is damaged indeed, or this is merely a configuration issue.

You may want to check the configuration in the AD1PCFG register. If you already did and everything seems fine, then it's probably a physical damage.

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