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how is the analog input and the 10 bits digital output related? i provided a 2V analog into PORTA, pin 0 and the output i obtained was actually 01 1001 1101 => 413 in decimal! can anyone provide any enlightenment? |
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ADC module in PIC16F87
Started by ●January 30, 2004
Reply by ●January 30, 20042004-01-30
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The reference is probably Vdd (+5V). 10bit (2 to the power of 10)
means that you have 1024 equal steps between 0 & 5V, each step is
approximately 5mV. Therefore, 413 (steps) is equal to
2V.
Regards
Ian
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Reply by ●January 30, 20042004-01-30
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Hi Ian, Thanks a lot for the great reply. Short and sweet, straight to the point! I have one more question: What happens if instead of a +2V, I provide a -2V analog input? --- In , "I Forse" <i.forse@t...> wrote: > The reference is probably Vdd (+5V). 10bit (2 to the power of 10) means > that you have 1024 equal steps between 0 & 5V, each step is approximately > 5mV. Therefore, 413 (steps) is equal to 2V. > > Regards > > Ian > -----Original Message----- > From: nibnewux [mailto:nibnewux@y...] > Sent: 30 January 2004 11:50 > To: > Subject: [piclist] ADC module in PIC16F87 > how is the analog input and the 10 bits digital output related? > i provided a 2V analog into PORTA, pin 0 and the output i obtained > was actually 01 1001 1101 => 413 in decimal! > > can anyone provide any enlightenment? > > to unsubscribe, go to http://www.yahoogroups.com and follow the > instructions > -------------------------------- -------- > -- > Yahoo! Groups Links > > a.. To > -- > Outgoing mail is certified Virus Free. > Checked by AVG Anti-Virus (http://www.grisoft.com). > Version: 7.0.211 / Virus Database: 261.8.1 - Release Date: 30/01/04 |
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Reply by ●January 31, 20042004-01-31
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0V = lowest limit = 0 steps 5V = highest limit = 1024 steps -2V? It's under 0V so you'll get a 0 out of it, or, it'll blow up the pin if it's not protected. Check the docs on the chip and see what the absolute minimums are for the circuit. You should protect it around those limits if it doesn't do so internally. I think the 16F88 has the ADC on it doesn't it? It also allows programmable VREF- and VREF+. So you COULD set your low reference under -2V if you really need to convert voltage under that value. Put your minimum on the VREF- pin and your maximum on the VREF+ pin. Your steps move appropriately. > -----Original Message----- > From: nibnewux [mailto:] > Sent: Friday, January 30, 2004 6:32 PM > To: > Subject: [piclist] Re: ADC module in PIC16F87 > > Hi Ian, > > Thanks a lot for the great reply. Short and sweet, straight > to the point! > > I have one more question: What happens if instead of a +2V, I > provide a -2V analog input? > --- In , "I Forse" <i.forse@t...> wrote: > > The reference is probably Vdd (+5V). 10bit (2 to the power of 10) > means > > that you have 1024 equal steps between 0 & 5V, each step is > approximately > > 5mV. Therefore, 413 (steps) is equal to 2V. > > > > Regards > > > > Ian > > -----Original Message----- > > From: nibnewux [mailto:nibnewux@y...] > > Sent: 30 January 2004 11:50 > > To: > > Subject: [piclist] ADC module in PIC16F87 > > > > > > how is the analog input and the 10 bits digital output related? > > i provided a 2V analog into PORTA, pin 0 and the output i obtained > > was actually 01 1001 1101 => 413 in decimal! > > > > can anyone provide any enlightenment? > > |
