Embedded Programming

1. Programming Board

Blinking Code using Arduino environment


I started with code code from Jaclyn Berry's page :

  const int buttonPin = 7;
        const int ledPin = 2;

        int buttonState = 0;

        void setup() {
          pinMode(ledPin, OUTPUT);
          pinMode(buttonPin, INPUT);

        void loop() {
          buttonState = digitalRead(buttonPin);

          if (buttonState == HIGH){
The key steps to adapting this to my board are pretty simple. All I have to do is change the
pins to work with my board and to adjust certain board/programmer settings in the Arduino
environment. This diagram shows what the pins are named in the eyes of Arduino vs. what you 
see on the schematic.
Programming Board
My LED pin is A7 and my switch pin is A2. I changed the code to toggle between blinking or 
being a solid light based on the button press. 
My final code was this (.ino file linked here):

  const int buttonPin = A2; //define button locations
  const int ledPin = A7; //define LED location

  int buttonState = 0; //button state defined as low to start
  int count = 0; //set up a counter to change the LED state

  void setup() {
      pinMode(ledPin, OUTPUT); //set LED as output
      pinMode(buttonPin, INPUT); //set button as an input

  void loop() {
      buttonState = digitalRead(buttonPin); //read state of button
      //Blink option:
      if (buttonState == HIGH && count ==0){ //if button is off and you're on state1
      //Solid option:
      else if (buttonState == HIGH && count ==1){
      //When button is pressed:
        count = count +1;
        if (count >1){
 CONNECTING BOARD & PROGRAMMER: For this set up my settings under the Arduino tool menu were: 
Board: "ATtiny 24/44/84" Processor: "ATtiny44" Programmer: "USBTinyISP" (1) Arduino was not 
identifying my USBtiny & my programmer didn't seem to be getting powered properly. After 
trouble shooting for a while I realized one issue was that the connecting cable I made for my 
board and programmer wasn't working properly. When I got new wires and connected the two 
boards Arudino was able to find my board! The no longer working cable :'( :
2) Another key issue was that I did not have the driver downloaded for the USBtiny. When I 
went to computer connected devices I saw that it said that the driver was "unavailable", so I 
had to go online and download a driver- then it worked! love it. Here is what it showed in 
my "other devices" once I had the driver:

other devices
It successfully uploaded and the button could toggle between blinking the light or keeping it 
(2) Blinking Program using C-program & Makefile

I started with Rob Hart's code . This comes with both a C file and a make file. His code turns
on an LED in response to a button press

To adapt it I did the following:
(1) Toggle between a blinking state and a solid state
(2) Changed the pin assignments

Here is the code I wrote:


  #define bit_get(p,m) ((p) & (m))
  #define bit_set(p,m) ((p) |= (m))
  #define bit_clear(p,m) ((p) &= ~(m))
  #define BIT(x) (0x01 << (x))

    // Button  PA5 (pin 8).
    // LED     PB2 (pin 5).

  int main()

    bit_set(PORTA,BIT(5));  // Turn button pull up resistor on by setting PA5(input) high
    bit_set(DDRB,BIT(2));   // Enable output on the LED pin (PB2)

    while (1)
      if(bit_get(PINA,BIT(5)))  // Button is up, turn off
      else                      // Button is down, turn on

 Getting the c-stuff to work on my computer: I followed Julia Ebert's process for uploading 
C-programs to an Attiny44. ISSUES: (1) At first "make" didn't work. I had to follow 
the process here (written by Brian) that took me through installing the Atmel GNU Toolchain, 
installing GNU Make, installing avrdude, and updating my PATH. NOTE ON PATH: I was having 
issues with my PATHs even after exactly following this process above. When I tested 
"avr-gcc --version" in my terminal is said command not found. I found  this resource that 
showed me that you sometimes have to write the "Program Files" portion of the path as 
"PROGRA~1" to fix issues involving the space in the name. It worked! 
Happy PATHs:
Happy PATHs
(2) Now make was working and my paths were correct but I kept getting this error.

(2) Now make was working and my paths were correct but I kept getting this error.
After a lot of trouble shooting I realized that when I was downloading the echo files Windows 
was adding a .txt to the end of both files. In Atom I renamed the files and finally the make 
function worked, I got my hex file!:
I got my hex file
So to review, the process is as follows:
(1) Open terminal in directory w/ the C and make file
(2) Comile & make hex file  make -f hello.ftdi.44.echo.c.make  Now all I have to do is (3) 
Send the file to the board: make -f hello.ftdi.44.echo.c.make program-usbtiny  (4) Set the 
clock on the board: make -f hello.ftdi.44.echo.c.make program-usbtiny-fuses  ~~~~~~change 
the c and make file names to match the project you care about~~~~~~~~~ Embedded Programming I 
started to do for my final:  I started with Neil's blinking program (written in C). In this 
program an LED turns on in response to a button being pressed. I want to change it so that a 
button press makes a string of lights toggle between different color patterns. This will be 
integrated into my final project in the housing of the UFO buoy. I reconfigured my board to 
use this tri-colored LED Here is the C-Code I wrote to toggle the color changing LED:

 // Copied from Rab Hart's code that was...
  //Shamelessly copied and mofied from Neil Gershenfeld's for purposes of instruction.

  //This cycles the color pattern of LEDs in response to button press
  //For the ATTINY44

  // Button  PA2 (pin 8).
  // RED     PA7 (pin 5).
  // GREEN   PA6
  // BLUE    PA5

  #include < avr/io.h>       // this includes all definitions of registers and bits of 
registers, including pins and port names.

  #define output(directions,pin) (directions |= pin) // set port direction for output
  #define input(directions,pin) (directions &= (~pin)) // set port direction for input
  #define set(port,pin) (port |= pin) // set port pin
  #define clear(port,pin) (port &= (~pin)) // clear port pin
  #define pin_test(pins,pin) (pins & pin) // test for port pin
  #define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set

  #define input_port PORTA		   // The button is on port A
  #define input_direction DDRA	 //  DDRA defines input/output for port A
  #define input_pin (1 << PA2)	 //  The button is on pin 5 of port A    
(1<< PA5) = (1<< 5) = 0b00100000
  #define input_pins PINA			   //  PINA is the register 
that is read to detect input high or low.
  #define output_port PORTA		   //  port B will be used for the LED
  #define output_direction DDRA	 // DDRB defines input/output for port B
  #define output_red (1 << PA7)  //
  #define output_grn (1 << PA6)
  #define output_blu (1 << PA5)
  const int i = 0;

  int main(void) {
     // main function.

     // initialize pins

     output(output_direction, output_pin);        //  set output for LED pin.
     set(input_port, input_pin);                  // turn on internal pull-up
     input(input_direction, input_pin);           // set button pin for input.

     // main loop

     while (1) {

      if (pin_test(input_pins,input_pin))         //test button pin.
                        //  if button isn't pushed, stay how you are!

 I then did the same program in Arduino: The code I wrote in week 5 (onthe left) and the code 
I made for this type of blinking.
The code I wrote in week 5 (onthe left) and the code I made for this type of blinking.
I haven't uploaded these yet before I don't have the board built yet! But it as good practice 
in embedded progamming and hopefuly I won't have to change these too much when I have the 
board built for them to work.

2. Reading Datasheet & prepping final project board

For the programmer this week I used the board I made in week 5, but in my final project I will
be changing my board a lot and switching to the ATMEGA16U microcontroller.
This week I read the datasheet for the ATMEGA16U2-AU. These cost about $2 when you buy in 
Here is the datasheet for the ATMEGA16U. This is 300+ pages so I've highlighted the key 
information here:
This is an 8-bit AVR microcontroller. This means that all the messages it reads or writes are 
8-bits long. AVR is the specific family of microcrollers that this one belongs to. AVR 
microcontrollers run on the Harvard architecture system, where  separate memory systems are 
used to store instructions and data (Wikipedia page for Harvard Arch).

This is the 16K Byte version, so there are 16K Bytes of In-System Self-Programmable Flash 
(ISP Flash).

Here is the block diagram of the microcontroller:
Here is the block diagram of the microcontroller:
The listed features are:
  8K/16K/32K Bytes of In-System Programmable Flash with Read-While-Write capabilities
    allows the program memory to be reprogrammed in-system through an SPI serial
interface, by a conventional nonvolatile memory programmer, or by an on-chip Boot program
running on the AVR core
  512/512/1024 Bytes EEPROM,
  512/512/1024 SRAM,
  22 general purpose I/O lines
  32 general purpose working registers
  two flexible Timer/Counters with compare modes and PWM
  one USART
  a programmable Watchdog Timer with Internal Oscillator
  an SPI serial port
  debug WIRE interface (also used for accessing the On-chip Debug system and programming and 
five software selectable power saving modes)

Here is the pinout of the microcontroller:
Here is the pinout of the microcontroller
Let's talk about this pin out shall we!!

GND and V_CC (pins 3 and 4, switched between the two different configs) are the ground and 
power of the microcontroller.
the ground and power of the microcontroller
I added an LED to indicate when the chip is being powered and a bypass cap to gnd.

AVCC (pin 32) is the power source to the analog pins. I think of this like Analog + VCC.
I think of this like Analog + VCC
Port B pins (pins PB7-PB0, pins 14-21 for both pinout configs) "Port B is an 8-bit 
bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B 
output buffers have symmetrical drive characteristics with both high sink and source 
capability. As inputs, Port B pins that are externally pulled low will source current if the 
pull-up resistors are activated. The Port B pins are tri-stated when a reset condition 
becomes active, even if the clock is not running" So these pins can act as input or output 
ports, as defined by the used in embedded programming.
the used in embedded programming.
Pins 17, 16, and 15 are the MISO, MOSI, and SCLK pins for communicating with the programmer. 
Here is connect them to a 6-pin header for interfacing to the programmer (either the one from 
week 5 or the Atmel-ICE (AVR) in the lab). Ideally I'd like to program my board on my own 
some day, so being able to program w/ an arduino would be really nice. 
There are a ton of articles online on how exactly to do this.  You can also program this chip 
via USB port because it comes with DFU (device fireware updater) bootloader. I'm not sure what
approach will be beter for me. I'm still inteimiadated by setting fuses, make files, etc. The 
arduino route is certainly less involved/intimidating.
The arduino route is certainly less involved/intimidating.
Port C pins (pins PC7-PC0, pin locations a little spreadout for both pinout configs) These 
pins act just like port B pins. Recall pins can have alternate functions! PC0 is the XTAL2 
pin, PC1 is reset.
Port C pins
big questions... where is PC3???

Port D pins (pins PD7-PD0, pins 6-13 for both configs)
This port serves as the analog inputs to the analog comparator. What's an analog comparator?
It's this (and we can see it on the left side of the block diagram):
It's this (and we can see it on the left side of the block diagram)
"An analog comparator can be used to compare two voltage levels and based on that it can be 
used to generate a logic output (0 or 1) to indicate which of the two levels is higher or 
lower than the other."  Source
The Analog Comparator compares the input values on the positive pin AIN0(PD0) and negative 
pin AIN1 (PD1). When the voltage on the positive pin AIN0 is higher than the voltage on the 
negative pin AIN1, the Analog Comparator output, ACO, is set (bit 5 of the Analog Comparator 
Control and Status Register).
bit 5 of the Analog Comparator Control and Status Register
If the analog comparator is not used (PD2/PD1 pins) Port D acts just like port B or C. I'm 
not using the analog comparator!

There are 22 programmable Input/Output (aka I/O) pins.
The 22-programmable pins are coming out of the PORTD, PORTC, and PORTB drivers.

D+ and D- pins (pins 29 and 30) These are the USB Full Speed Negative Data Upstream Port and 
Positive Data Upstream Ports, respectively.
Source: Embedded Programming

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Muhammad Bilal

I am highly skilled and motivated individual with a Master's degree in Computer Science. I have extensive experience in technical writing and a deep understanding of SEO practices.

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