AVR arduino dasar

Lecture 6 – Introduction to the
ATmega328 and Ardunio
CSE P567

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

AVR Architecture
 Clocks and Power
 Beyond scope of this
course

AVR Architecture
 CPU
 Details coming

AVR Architecture
 Harvard architecture
 Flash – program memory
 32K
 SRAM – data memory
 2K
 EEPROM
 For long-term data
 On I/O data bus

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

AVR CPU
 Instruction Fetch
and Decode

AVR CPU
 I/O and special
functions

AVR Register File
 32 8-bit GP registers
 Part of SRAM memory space

Special Addressing Registers
 X, Y and Z registers
 16-bit registers made using registers 26 – 31
 Support indirect addressing

AVR Memory
 Program memory – Flash
 Data memory - SRAM

Addressing Modes
 Direct register
addressing

Addressing Modes
 Direct I/O addressing

Addressing Modes
 Direct data memory addressing

Addressing Modes
 Direct data memory with displacement addressing

Addressing Modes
 Indirect data memory addressing

Addressing Modes
 Indirect data memory addressing with pre-decrement

Addressing Modes
 Indirect data memory addressing with post-increment

Addressing Modes
 Program memory addressing (constant data)

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

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

Simple 2-Stage Pipeline
 Branch/Skip??

Single-Cycle ALU Instructions
 Most instructions execute in one cycle
 Makes program timing calculations (relatively) easy
 No cache misses
 1 clock/instruction

Addressing Modes
 JMP, CALL – Direct Program Memory Addressing

Addressing Modes
 IJMP, ICALL – Indirect program memory addressing

Addressing Modes
 RJMP, RCALL – Relative program memory addressing

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…

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

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

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

Pin Input
off
DDRx = 0
PORTx
PINx

Synchronization Timing
 Note: Takes a clock cycle for data output to be reflected
on the input

Pin Output
on
DDRx = 1
PORTx
PINx

Pin Input – PORT controls pullup
off
DDRx = 0
PORTx
PINx

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.

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

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

AVR Architecture
 Analog inputs
 Convert voltage to a
10-bit digital value
 Can provide reference
voltages

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

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

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;

AVR Architecture
 Special I/O support
 Serial protocols
 Uses special pins
 Uses timers
 Beyond scope of this
course

Arduino C Programs
 Arduino calls these “sketches”
 Basically C with libraries
 Program structure
 Header: declarations, includes, etc.
 setup()
 loop()
 Setup is like Verilog initial
 executes once when program starts
 loop() is like Verilog always
 continuously re-executed when the end is reached

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
}

The Arduino C++ Main Program
int main(void)
{
init();
setup();
for (;;)
loop();
return 0;
}

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

AVR arduino dasar

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