Subject: Questions regarding the PIC16C77X and its built in ADC
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
NNTP-Posting-Date: Sun, 22 Sep 2002 03:47:38 GMT
Organization: AT&T Broadband
Date: Sun, 22 Sep 2002 03:47:38 GMT
I have a few questions in regards to ADC capable PICs (in regards to the
project mentioned below). Unfortunately, my knowledge is lacking (although I
am trying to correct that), so bare with me.
What I would like to do is sample the signal from a telephone, using the
built in ADC in a Microchip PIC. Since human speech usually is below 4000
hz, the minimum sample rate I would need is 8,000 samples per second. Since
the signal itself's highest frequency should be around 4000 hz, a 12 bit
resolution (4096 possible values) should work. Is this correct?
I have been looking at the PIC16C77X MCUs.. I was also looking at the PDF
So here are some more somewhat basic questions:
The pinout diagram shows pins 11 as AVdd, pin 12 as AVss, pin 4 as VRef- and
pin 5 as VRef+. These are all of the pins specifically for the ADC part of
things, correct? I wish to have a telephone connected via a standard
telephone cord to an RJ11 jack on a standalone unit (with among other things
the PIC in it). A 9V power supply will be used to power the phone line.
Since 9v is way too much to connect to the AD on the PIC (correct?), a
resistor will need to be used to get it below the 4.096V level (which is the
max voltage level for AVDD,AVSS right?).
So, basically I was thinking the negative terminal on the battery can be
connected to the RING pin on the RJ11 jack, and the TIP pin on the jack can
be connected to the Avdd pin on the PIC, and have the AVss pin connected to
the positive terminal on the battery... I would need a resistor inbetween
the RJ11 TIP pin and the AVDD pin (correct?)..
I have the bad feeling that I have something (lots of things?) backward
however (hence the reason for this post).. I also don't know what to use for
VREF + or VREF -...
If someone would care to point out the mistakes I made above, point me in
the right direction etc.. that would be great!