DM240002 Microchip Technology, DM240002 Datasheet - Page 23

• Manufacturer Part Number: DM240002
• Description: BOARD DEV EXPLORER 16 44-PIN
• Manufacturer: Microchip Technology
• Series: Explorer 16 44-pinr
• Type: MCUr

Specifications of DM240002

• Contents: Explorer 16 Dev Board, PIC24FJ64GA004 and dsPIC33FJ32GP204 PIM Modules
• Processor To Be Evaluated: PIC24FJ128GA010, dsPIC33FJ256GP710
• Processor Series: PIC 24, dsPIC33
• Data Bus Width: 32 bit
• Interface Type: RS-232
• Silicon Manufacturer: Microchip
• Core Architecture: PIC, DsPIC
• Core Sub-architecture: PIC24, DsPIC33
• Silicon Core Number: PIC24F, DsPIC33F
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: dsPIC30, dsPIC33, PIC32, PIC24FJ, PIC24HJ
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

© 2007 Microchip Technology Inc.
3.2.4
This lesson shows how to configure the ADC, run a conversion, read the analog voltage
controlled by the potentiometer (RP1) on the board, and display the high order 8 bits
on the display.
The PIC16F887 has an on-board Analog-to-Digital Converter (ADC) with 10 bits of res-
olution on any of 14 channels. The converter can be referenced to the device’s V
an external voltage reference. The 44-pin Demo Board references it to V
by the PICkit 2 Microcontroller Programmer. The answer from the ADC is represented
by a ratio of the voltage to the reference.
Converting the answer from the ADC back to voltage requires solving for V.
Two of the three factors on the right side of the equation are constants and may be cal-
culated in advance. This eliminates the need to actually divide, but still requires fixed
or floating point multiply to solve the equation on the fly.
However, sometimes, such as when reading a sensor, calculating the voltage is only
the first step. There may be additional math to calculate the meaningful data from the
sensor. For example, when reading a thermistor, calculating the voltage is only the first
step on the way to getting the temperature.
There are other means to convert ADC values, including a straight table look-up or a
piece-wise linear interpolation. Each of these represents different speed/memory
trade-offs.
The schematic (Appendix A. “Hardware Schematics”) shows the wiper on the poten-
tiometer is connected to pin RA0 on the PIC16F887.
Here’s the checklist for this lesson:
• Configure PORTA as an analog input, TRISA<0> = 1, ANSEL<0> = 1
• Select justification and V
• Select clock scaling and channel in ADCON0.
ADC = V/V
V = ADC/1023 * V
Lesson 4: Analog-to-Digital
REF
* 1023
REF
REF
44-Pin Demo Board Lessons
source in ADCON1.
DS41296B-page 19
DD
as provided
DD
or