Arduino-Register Programming

Simple LED Blink Program

Here I'm explained my first register level coding, It is awesome and it's make me much more understand about how the microcontroller is working, I'm still learning, so here I'm sharing what I understood. Are you ready for this then let's go

Arduino language Blink program

This is simple Blink program without using any functions!. Take a look at the code the same code is converting to register level

unsigned long counter = 0;// initializing  counter variable and set to 0
void setup() {
  pinMode(LED_BUILTIN, OUTPUT);// set 13th pin LED as output
  Serial.begin(9600);// initializing Serial communications
}

void loop() {


  counter++;//increment the counter
  Serial.println(counter);// print the counter value on Serial monitor
  if (counter > 250) {
    digitalWrite(LED_BUILTIN, HIGH);// if counter value greater than 250 then LED turn ON
  }
  if (counter > 500) {
    digitalWrite(LED_BUILTIN, LOW);// if counter value greater than 500 then LED turn OFF
    counter = 0;// resetting the counter to 0
  }


}

Before going to Register level programming we have to understand some basics.

Port registers allow for lower-level and faster manipulation of the i/o pins of the microcontroller on an Arduino board. The chips used on the Arduino board is ATMEAG328 (Arduino Nano/UNO) have three ports

What is Ports?

For example ATMEGA328 (in Arduino Nano) have 32 pins and it has 3 Ports totally PORT B, PORT C and PORT D,

1. B (digital pin 8 to 13)
2. C (analog input pins)
3. D (digital pins 0 to 7)

PORT D

PORT D	0	1	2	3	4	5	6	7
ARDUINO PIN	0	1	2	3	4	5	6	7
ATMEGA PIN	30	31	32	1	2	9	10	11

PORT B

PORT B	0	1	2	3	4	5	6	7
ARDUINO PIN	8	9	10	11	12	13	20/XTAL1	21/XTAL2
ATMEGA PIN	12	13	14	15	16	17	7	8

PORT C

PORT C	0	1	2	3	4	5	6	7
ARDUINO PIN	A0/14	A1/15	A2/16	A3/17	A4/18	A5/19	22/RST
ATMEGA PIN	23	24	25	26	27	28	29

Each port is controlled by three registers, which are also defined variables in the Arduino language.

I can show simply in the table how the Arduino coding is different from Register coding.

ARDUINO CODING	REGISTER CODING
pinMode()	DDR
digitalWrite()	PORT
digitalRead()	PIN

I will explain that what is DDR, PORT & PIN.

DDR - data direction register – DDRx

The port input pins I/O location is read only, It means default all the ports are inputs, so if we want to  manipulate a pin to output we have to use Data Direction Register.