User manual
Table Of Contents
- Chapter 1. Overview
- 1.1 Introduction
- 1.2 Highlights
- 1.3 PICDEM™ Lab Development Kit Contents
- 1.4 PICDEM™ Lab Development Board Construction and Layout
- 1.5 Target Power
- 1.6 Connecting the PICkit™ 2 Programmer/Debugger
- 1.7 Solderless Prototyping Area Strip Configuration
- Chapter 2. Getting Started
- 2.1 Introduction
- 2.2 Prerequisites
- 2.3 The Software Control Loop
- 2.4 MPLAB® IDE Download Instructions
- 2.5 Installing the Included Lab Files
- Chapter 3. General Purpose Input/Output Labs
- 3.1 Introduction
- 3.2 General Purpose Input/Output Labs
- 3.3 GPIO Output Labs
- 3.3.1 Reference Documentation
- 3.3.2 Equipment Required for GPIO Output Labs
- 3.3.3 PICDEM Lab Development Board Setup for GPIO Output Labs
- Figure 3-1: PICDEM Lab Schematic for GPIO Output Labs
- 3.3.4 Lab 1: Light LEDs
- Figure 3-2: MAIN() Software Control Loop Flowchart for Lab 1
- Figure 3-3: Step One
- Figure 3-4: Step Two
- Figure 3-5: Step Three
- Figure 3-6: Step Four
- Figure 3-7: Summary
- Figure 3-8: Project Window
- Figure 3-9: PICkit 2 PROGRAMMER/DEBUGGER TOOLBAR
- Figure 3-10: Lab 1 LED Output
- 3.3.5 Lab 2: Flash LEDs (Delay Loop)
- Figure 3-11: Main() Software Control Loop Flowchart for Lab 2
- Figure 3-12: Timing() Delay Routine Flowchart for Lab 2
- 3.3.6 Lab 3: Simple Delays Using Timer0
- Equation 3-1: TMR0 Overflow Period using FOSC/4
- Equation 3-2: TMR0 Overflow Period when including the Prescaler
- Equation 3-3: Calculating a TMR0 PreLoad Value to generate a 10mS Overflow Period
- Figure 3-13: Delay_10mS() using Timer0
- Equation 3-4: Maximum TMR0 Overflow Period
- Figure 3-14: Delay_1S() using Timer0
- 3.3.7 Lab 4: Rotate LEDs
- Figure 3-15: Main() Software Control Loop Flowchart for Lab 4
- Figure 3-16: Decide() Flowchart for Lab 4
- Figure 3-17: Results of Do_Output()
- 3.4 GPIO Input Labs
- 3.4.1 Reference Documentation
- 3.4.2 Equipment Required for GPIO Input Labs
- 3.4.3 PICDEM Lab Development Board Setup for GPIO Input Labs
- Figure 3-18: PICDEM Lab Schematic for GPIO Input Labs
- 3.4.4 Lab 5: Adding a Push Button
- Figure 3-19: Main() Software Control Loop Flowchart for Lab 5
- Figure 3-20: Get_Inputs() Software Flowchart for Lab 5
- Figure 3-21: Delay_5mS() Software Flowchart for Lab 5
- Figure 3-22: Decide() Software FlowChart for Lab 5
- 3.4.5 Lab 6: Push Button Interrupt
- Figure 3-23: Main() Software Control Loop Flowchart for GPIO Lab 6
- Figure 3-24: pb_pressISR() for Lab 6 Showing Switch Debounce
- 3.4.6 Lab 7: Push Button Interrupt-on-Change
- Figure 3-25: pb_pressisr Flowchart for Lab 7
- 3.4.7 Lab 8: Using Weak Pull-Ups
- Chapter 4. Comparator Peripheral Labs
- 4.1 Introduction
- 4.2 Comparator Labs
- 4.2.1 Reference Documentation
- 4.2.2 Comparator Labs
- 4.2.3 Equipment Required
- 4.2.4 Lab 1: Simple Compare
- Figure 4-1: Schematic for Comparator Lab 1
- Figure 4-2: Main() software Control Loop Flowchart for Comparator Lab 1
- 4.2.5 Lab 2: Using the Comparator Voltage Reference
- Equation 4-1: CVref Output Voltage
- Equation 4-2: Calculating a 2.5V Internal Reference (Low-Range Method)
- Figure 4-3: Schematic for Comparator Lab 2
- 4.2.6 Lab 3: Higher Resolution Sensor Readings Using a Single Comparator
- Figure 4-4: Basic Relaxation Oscillator Circuit
- Figure 4-5: Schematic for Comparator Lab 3
- Figure 4-6: Main() software Control Loop Flowchart for Comparator Lab 3
- Figure 4-7: TMR0_ISR Flowchart for Comparator Lab 3
- Chapter 5. Analog-to-Digital Converter Peripheral Labs
- 5.1 Introduction
- 5.2 ADC Labs
- Figure 5-1: Schematic for ADC Lab 1
- Figure 5-2: Main() software Control Loop Flowchart for Comparator Lab 1
- Figure 5-3: Main() software Control Loop Flowchart for Comparator Lab 1
- Figure 5-4: ADC Result Bit Significance
- Figure 5-5: Schematic for ADC Lab 2
- Figure 5-6: Main() software Control Loop Flowchart for ADC Lab 2
- Appendix A. Schematic
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Analog-to-Digital Converter Peripheral Labs
© 2009 Microchip Technology Inc. DS41369A-page 85
5.2.4 Lab 2: Audible Temperature Sensor
5.2.4.1 OVERVIEW
In this lab, the ADC peripheral on the PIC16F690 is used to alter the frequency of
Pulse-Width Modulated Waveform (PWM) in relation to the temperature sensed by a
thermistor connected to the input of the ADC peripheral. The PWM waveform is gener-
ated by simply toggling the RC0 voltage level high and low. The thermistor is used to
create a voltage divider in conjunction with a 1KΩ
resistor to vary the voltage into the
ADC input. This thermistor is a Negative Temperature Coefficient type (NTC) meaning
that as the temperature of the device increases, the resistance effectively decreases.
The voltage drop across the thermistor is converted by the ADC and the ADRESH
result then used to manipulate a TMR0 preload value (see GPIO Lab 3) that will be
used in the Timing() to vary the execution speed of the software control loop and ulti-
mately the frequency of the PWM waveform. The PWM will be connected to an
N-Channel MOSFET used to drive the 8Ω
speaker on the PICDEM Lab Development
Board. The schematic for this lab is shown in Figure 5-5.
FIGURE 5-5: SCHEMATIC FOR ADC LAB 2
Referring to the schematic in Figure 5-5, the RC0 connects to the gate of the IRFD010
N-Channel MOSFET Q1. Resistor R4 pulls the gate input low ensuring the transistor
will remain OFF until a high voltage level is present on the RC0 output. When the PWM
transitions high, Q1 is ON and current flows through the 8Ω
speaker. The 100Ω R3
resistor is used to limit the current through the speaker to maintain manufacturer spec-
ified power ratings. In this way, any change in temperature around the thermistor will
alter the frequency of the PWM, thereby changing the audible frequency emitted from
the speaker.
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J9J8
V
DD
R1
1KΩ
V
SS
RB4/AN10
U2
RC0
V
SS
V
DD
R3
100Ω
8Ω
R2
10KΩ
J19
SP+
SP-
LS1
Thermistor
Q1
IRFD010 N-Channel
MOSFET
V
SS
R4
10KΩ