Week #8: Embedded programming

Our tasks for the eighth week were:
  1. Read a microcontroller datasheet
  2. Program the board that was built in Week #6 to do something
I downloaded and studied (not page by page, obviously) the ATtiny44 datasheet. This was, actually, a big step in my learning process. If I want to learn something, I can't just copy what someone else did; so, it was really important to understand how the ATtiny44 works.

The first test was really simple: to turn the green led on for a second, then off for another second, an so on.

To do that, I used Arduino IDE 1.8.1. First, I had to download the ATTINY44 board, set the clock to 20 MHz and record the bootloader.

Programming the PCB

Then, I uploaded the following code:

void setup() {

  pinMode(11, OUTPUT); // ATTINY44 PA2

  #define GLED 11

}

 

void loop() {

  digitalWrite(GLED, HIGH);  

  delay(1000);               

  digitalWrite(GLED, LOW);

  delay(1000);                  

}


And, to my satisfaction, it worked! You can see a video below:


Then, I proceeded to a more elaborate test: once the button is pressed, each one of the LEDs turns on for a second, in a sequence. This is the code:

int botao = 0;

void setup() {   

  pinMode(5, OUTPUT); // ATTINY44 PB2

  pinMode(6, OUTPUT); // ATTINY44 PA7

  pinMode(10, INPUT); // ATTINY44 PA3

  pinMode(11, OUTPUT); // ATTINY44 PA2

  #define WLED 5

  #define RLED 6

  #define BUTTON 10

  #define GLED 11

}

 

void loop() {

  botao = digitalRead(BUTTON);

  if ( BUTTON == HIGH ) {

    digitalWrite(WLED, HIGH);  

    delay(1000);               

    digitalWrite(WLED, LOW);

    delay(1000);                  

    digitalWrite(RLED, HIGH);  

    delay(1000);               

    digitalWrite(RLED, LOW);

    delay(1000);               

    digitalWrite(GLED, HIGH);  

    delay(1000);               

    digitalWrite(GLED, LOW);

    delay(1000);               

}


At first, everything seemed to have worked out, as I had no problems to upload this new code. But, when I pressed the button, nothing happend. I changed a few lines in the code and tried again, but this time I couldn't even upload the file. After Kenzo and I performed a few tests, we came to the sad conclusion that something, probably the microcontroller, burned due to a short-circuit triggered by pressing the button.

As I had fallen behind with other assignments, I chose to consider this assignment completed, since I would have other opportunities to design and program these boards.

I must confess that I finished this assignment with lots of doubts. Even though the programming itself was very clear to me, upon completion of the task I still could not understand precisely what the hardware I built did - to be quite honest, I couldn't even understand the need for two PCBs!

But, as I progressed during the course, specially while developing my final project, all these doubts were cleared. Not only I learned the difference between the programmer board and the programmed board, but I also learned how to communicate with a PC using a serial port, which was essential for my final project.