Lecture6
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This document provides an outline and overview of the topics that will be covered in Lecture 6 of the CSE P567 course, including the ATmega328 architecture, I/O pins, the Arduino C++ language, and timing functions. It discusses the ATmega328's Harvard architecture with separate flash, SRAM, and EEPROM memory spaces. It describes the AVR CPU, registers, addressing modes, instruction set, and I/O functionality. It also covers the Arduino development board's pin mapping and digital/analog I/O functions.
![Stack Pointer Register
Special register in I/O space [3E, 3D]
Enough bits to address data space
Initialized to RAMEND (address of highest memory address)
Instructions that use the stack pointer](https://image.slidesharecdn.com/lecture6-140715041502-phpapp01/85/Lecture6-23-320.jpg)
![Arduino Digital and Analog I/O Pins
Digital pins:
Pins 0 – 7: PORT D [0:7]
Pins 8 – 13: PORT B [0:5]
Pins 14 – 19: PORT C [0:5] (Arduino analog pins 0 – 5)
digital pins 0 and 1 are RX and TX for serial communication
digital pin 13 connected to the base board LED
Digital Pin I/O Functions
pinMode(pin, mode)
Sets pin to INPUT or OUTPUT mode
Writes 1 bit in the DDRx register
digitalWrite(pin, value)
Sets pin value to LOW or HIGH (0 or 1)
Writes 1 bit in the PORTx register
int value = digitalRead(pin)
Reads back pin value (0 or 1)
Read 1 bit in the PINx register](https://image.slidesharecdn.com/lecture6-140715041502-phpapp01/85/Lecture6-53-320.jpg)
Lecture6
- 1. Lecture 6 – Introduction to the ATmega328 and Ardunio CSE P567
- 2. Outline Lecture 6 ATmega architecture and instruction set I/O pins Arduino C++ language Lecture 7 Controlling Time Interrupts and Timers Lecture 8 Guest lecture – Radio communication Lecture 9 Designing PID Controllers
- 4. AVR Architecture Clocks and Power Beyond scope of this course
- 5. AVR Architecture CPU Details coming
- 6. AVR Architecture Harvard architecture Flash – program memory 32K SRAM – data memory 2K EEPROM For long-term data On I/O data bus
- 7. Memory Flash (32K) (15-bit addresses) Program memory – read only Non-volatile Allocate data to Flash using PROGMEM keyword see documentation SRAM (2K) Temporary values, stack, etc. Volatile Limited space! EEPROM (1K) Long-term data see documentation on EEPROM library
- 8. AVR CPU Instruction Fetch and Decode
- 9. AVR CPU ALU Instructions
- 10. AVR CPU I/O and special functions
- 11. AVR Register File 32 8-bit GP registers Part of SRAM memory space
- 12. Special Addressing Registers X,Y and Z registers 16-bit registers made using registers 26 – 31 Support indirect addressing
- 13. AVR Memory Program memory – Flash Data memory - SRAM
- 14. Addressing Modes Direct register addressing
- 15. Addressing Modes Direct I/O addressing
- 16. Addressing Modes Direct data memory addressing
- 17. Addressing Modes Direct data memory with displacement addressing
- 18. Addressing Modes Indirect data memory addressing
- 19. Addressing Modes Indirect data memory addressing with pre-decrement
- 20. Addressing Modes Indirect data memory addressing with post-increment
- 21. Addressing Modes Program memory addressing (constant data)
- 23. Stack Pointer Register Special register in I/O space [3E, 3D] Enough bits to address data space Initialized to RAMEND (address of highest memory address) Instructions that use the stack pointer
- 24. Program Status Register (PSR) Status bits set by instructions/Checked by Branch/Skip instructions I – Global interrupt enable T – Flag bit H – Half carry (BCD arithmetic) S – Sign V – Overflow N – Negative Z – Zero C – Carry
- 25. Simple 2-Stage Pipeline Branch/Skip??
- 26. Single-Cycle ALU Instructions Most instructions execute in one cycle Makes program timing calculations (relatively) easy No cache misses 1 clock/instruction
- 27. Addressing Modes JMP, CALL – Direct Program Memory Addressing
- 28. Addressing Modes IJMP, ICALL – Indirect program memory addressing
- 29. Addressing Modes RJMP, RCALL – Relative program memory addressing
- 32. Jump and Call Instructions
- 33. Skip and Branch Instructions
- 34. Skip and Branch (cont)
- 35. Move, Load
- 36. Store
- 39. Shift and Bit Instructions
- 41. AVR Architecture Three timers Very flexible Choose clock rate Choose “roll-over” value Generate interrupts Generate PWM signals (represent 8-bit value with using a clock signal) More in next lecture…
- 42. Arduino Timing Functions delay(ms) wait for ms milliseconds before continuing delayMicroseconds(us) wait for us microseconds before continuing unsigned long millis( ) return number of milliseconds since program started unsigned long micros( ) return number of microseconds since program started resolution of 4 microseconds
- 43. AVR Architecture Interface to pins Each pin directly programmable Program direction Program value Program pull-ups Some pins are special Analog vs. Digital Clocks Reset
- 44. I/O Ports 3 8-bit Ports (B, C, D) Each port controlled by 3 8-bit registers Each bit controls one I/O pin DDRx – Direction register Defines whether a pin is an input (0) or and output (1) PINx – Pin input value Reading this “register” returns value of pin PORTx – Pin output value Writing this register sets value of pin
- 45. Pin Circuitry
- 46. Pin Input off DDRx = 0 PORTx PINx
- 47. Synchronization Timing Note:Takes a clock cycle for data output to be reflected on the input
- 48. Pin Output on DDRx = 1 PORTx PINx
- 49. Pin Input – PORT controls pullup off DDRx = 0 PORTx PINx
- 50. I/O Ports Pullups If a pin is an input (DDRxi = 0): PORTxi = 0 – pin is floating PORTxi = 1 – connects a pullup to the pin Keeps pin from floating if noone driving Allows wired-OR bus Individual bits can be set cleared using bit-ops A bit can be toggled by writing 1 to PINxi SBI instruction e.g.
- 51. I/O Protection
- 53. Arduino Digital and Analog I/O Pins Digital pins: Pins 0 – 7: PORT D [0:7] Pins 8 – 13: PORT B [0:5] Pins 14 – 19: PORT C [0:5] (Arduino analog pins 0 – 5) digital pins 0 and 1 are RX and TX for serial communication digital pin 13 connected to the base board LED Digital Pin I/O Functions pinMode(pin, mode) Sets pin to INPUT or OUTPUT mode Writes 1 bit in the DDRx register digitalWrite(pin, value) Sets pin value to LOW or HIGH (0 or 1) Writes 1 bit in the PORTx register int value = digitalRead(pin) Reads back pin value (0 or 1) Read 1 bit in the PINx register
- 54. Arduino Analog I/O Analog input pins: 0 – 5 Analog output pins: 3, 5, 6, 9, 10, 11 (digital pins) Analog input functions int val = analogRead(pin) Converts 0 – 5v. voltage to a 10-bit number (0 – 1023) Don’t use pinMode analogReference(type) Used to change how voltage is converted (advanced) Analog output analogWrite(pin, value) value is 0 – 255 Generates a PWM output on digital pin (3, 5, 6, 9, 10, 11) @490Hz frequency
- 55. AVR Architecture Analog inputs Convert voltage to a 10-bit digital value Can provide reference voltages
- 56. PWM – Pulse Width Modulation Use one wire to represent a multi-bit value A clock with a variable duty cycle Duty cycle used to represent value We can turn it into a analog voltage using an integrating filter
- 57. Port Special Functions Lots of special uses for pins Clock connections Timer connections e.g. comparator output for PWM Interrupts Analog references Serial bus I/Os USART PCI
- 58. Reading and Writing Pins Directly Only one pin can be changed using the Arduino I/O functions Setting multiple pins takes time and instructions To change multiple pins simultaneously, directly read/write the pin registers DDR{A/B/C} PORT{A/B/C} PIN{A/B/C} e.g. to set all digital pins 0 – 7 to a value: PORTD = B01100101;
- 59. AVR Architecture Special I/O support Serial protocols Uses special pins Uses timers Beyond scope of this course
- 60. Arduino C Programs Arduino calls these “sketches” Basically C with libraries Program structure Header: declarations, includes, etc. setup() loop() Setup is likeVerilog initial executes once when program starts loop() is likeVerilog always continuously re-executed when the end is reached
- 61. Blink Program int ledPin = 13; // LED connected to digital pin 13 // The setup() method runs once, when the sketch starts void setup() { // initialize the digital pin as an output: pinMode(ledPin, OUTPUT); } // the loop() method runs over and over again, // as long as the Arduino has power void loop() { digitalWrite(ledPin, HIGH); // set the LED on delay(1000); // wait for a second digitalWrite(ledPin, LOW); // set the LED off delay(1000); // wait for a second }
- 62. The Arduino C++ Main Program int main(void) { init(); setup(); for (;;) loop(); return 0; }
- 63. Arduino Serial I/O Communication with PC via USB serial line Use the Serial Monitor in the IDE Or set up a C or Java (or you-name-it) interface Example Serial library calls Serial.begin(baud-rate) 9600 default Serial.println(string) int foo = Serial.read() Read one byte (input data is buffered) See documentation for more
- 64. Example Program