Hệ thống nhúng - Chương 1 pot
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Hệ thống nhúng
Thạc sĩ Lê Mạnh Hải
Embedded Systems
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Môû ñaàu
I Mục đích môn học:
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Cung cấp kiến thức về lập trình nhúng trên Microchip PIC24
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Rèn luyện kỹ năng đọc sách chuyên ngành bằng tiếng Anh
II. Thời gian:
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30 tiết lý thuyết (3 ĐVHT) + 30 tiết thực hành
III Giáo trình và tài liệu tham khảo
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Programming 16-Bit PIC Microcontrollers in C: Learning to Fly the
PIC24. Lucio Di Jasio. Elsevier. 2007
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Designing Embedded Systems with PIC Microcontrollers. Principles
and applications.Tim Wilmshurst. Elsevier. 2007
IV. Đánh giá:
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Thi kết thúc môn:70%. Có một bài báo cáo kỹ thuật.
•
V. Giáo viên:
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Thạc sĩ Lê Mạnh Hải. Tel: 0985399000. Không gọi điện thoại để hỏi
hay xin điểm, email:
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Lesson 1 : THE FIRST FLIGHT
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Flight plan: Every flight should have a purpose
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PIC24 16-bit microcontroller PIC24FJ128GA010
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MPLAB® IDE
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MPLAB C30
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The flight
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Our first line of code is going to be:
#include <p24fj128ga010.h>
This is not yet a proper C statement, but more of a pseudo-
instruction for the preprocessor telling the compiler to
read the content of a device-specific file before
proceeding any further. The content of the device-specifi
c “.h” file chosen is nothing more than a long list of the
names (and sizes) of all the internal special-function
registers (SFRs) of the chosen PIC24 model.
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C programming
Going back to our “Hello.c” source fi le, let’s add a couple more lines
that will introduce you to the main() function:
1. main()
2. {
3. }
We said our mission was to turn on one or more I/O pins: say PORTA,
pins RA0–7. In assembly, we would have used a pair of mov
instructions to transfer a literal value to the output port. In C it is
much
easier—we can write an “assignment statement” as in the following
example:
1. #include <p24fj128ga010.h>
2. main()
3. {
4. PORTA = 0xff;
5. }
Is it correct?
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Compiling and linking
•
This operation is called a Project Build. The sequence of events
is fairly long and complex, but it is composed mainly of two
steps:
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Compiling: The C compiler is invoked and an object code file
(.o) is generated. This file is not yet a complete executable.
While most of the code generation is complete, all the addresses
of functions and variables are still undefi ned. In fact, this is
also called a relocatable code object. If there are multiple
source files, this step is repeated for each one of them.
•
Linking: The linker is invoked and a proper position in the
memory space is found for each function and each variable.
Also any number of precompiler object code fi les and standard
library functions may be added at this time as required. Among
the several output files produced by the linker is the actual
binary executable file (.hex).
•
All this is performed in a very rapid sequence as soon as you
select the option “Build All” from the Project menu.
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Data
Sheet
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8
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PORT initialization
1. main()
2. {
3. TRISA = 0; // all PORTA pins output
4. PORTA = 0xff;
5. }
Question 1: How many bit does PORTA have?
Question 2: How to set all pins of PORTA?
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Testing PORTB
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Most of PORTB pins are multiplexed with the
analog inputs of the analog-to-digital converter
(ADC) peripheral. The 8-bit architecture reserved
PORTA pins primarily for this purpose—the roles
of the two ports have been swapped!
1. #include <p24fj128ga010.h>
2. main()
3. {TRISB = 0; // all PORTB pins output
4. AD1PCFG = 0xffff; // all PORTB pins digital
5. PORTB = 0xff;}
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Exercises
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If you have the Explorer16 board:
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Use the ICD2 Debugging Checklist to help you prepare the project for
debugging.
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To test the PORTA example, connect the Explorer16 board and check the
visual output on LED0–7.
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To test the PORTB example, connect a voltmeter (or DMM) to pin RB0 and
watch the needle move as you single-step through the code.
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Development Tools
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Quiz
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How many ports does PIC24FJ126GA010 have?
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What are differences between PORTA and PORTB
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How to set PORTB to be DIGITAL INPUT?
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What is next?
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CHAPTER 2: A LOOP IN THE PATTERN
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An animated simulation
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Using the Logic Analyzer
