To blink or not to blink :)

HW Platform to be used

Microchip(formerly ATMEL) 328P Controller

      This post is yet another blinky program on popular Microchip ATMEGA 328p micro controller. We will be using Arduino nano board for our experiment. Since the HW is readily available we can concentrate on writing our first program for blinking the LED!

Software development environment for blinky

      We will be using Bare metal programming technic to program the microcontroller. we will need below tools for the development.

      I will be using Zorin OS, which is a linux distribution based on ubuntu platform. You can download a copy of this linux flavour here for free :blush: Instructions given in this blog should work on most of the ubuntu flavoured OSs.

1. Compiler
2. Programmer software
3. Your favourite code editor!

Software Tools Setup

AVR GCC Compiler

      We will be using AVR GCC compiler which is based on a open source compiler developed by free software foundation(FSF). Full form of GCC is GNU Compiler Collection. GCC compiler can used for many languages like, C, C++ etc.

      Goto Microchip website and download latest version of AVR GCC compiler for linux.

      If you need to check whether your linux OS is 32bit or 64bit you can execute below command.

$ uname -m
x86_64

      So, i will be downloading 64bit avr-gcc toolchain AVR 8-bit Toolchain 3.6.2 - Linux 64-bit, which is latest(and greatest), at the time of this writing.

      Let’s install the downloaded setup file ‘avr8-gnu-toolchain-3.6.2.1778-linux.any.x86_64.tar.gz’ in linux now. Below set of commands will install the avr-gcc compiler on your PC.

tar -xzf avr8-gnu-toolchain-3.6.2.1778-linux.any.x86_64.tar.gz

Update the PATH variable to AVR-GCC tool folder

$ nano ~/.bashrc

!!! Beware, you will break the bash command execution if you overwrite PATH variable!!!

add at the end of the file to update PATH variable with avr-gcc compiler path

export PATH=$PATH:/home/tools/avr8-gnu-toolchain-linux_x86_64/bin/

A quick check for avr-gcc version can now be done.

$ avr-gcc –version
avr-gcc (AVR_8_bit_GNU_Toolchain_3.6.2_1778) 5.4.0
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Rejoice, your avr-gcc compiler set up is now complete :)

AVR Libc & Binutils

Unfortunately, we can not use the compiler installation we did just now! We need to still install avr-libc & avr-binutils

avr libc provides c runtime libraries for AVR controllers. Binutils is binary utilities to handle AVR binary files.

$ sudo apt-get install avr-libc binutils-avr

AVR Programmer utility: AVRDUDE

      We need a programmer software to burn our compiled program into AVR chips. We will be using avrdude software for this. Installation is fairly simple and straight forward. you can install avr dude using below command in terminal.

$ sudo apt-get install avrdude

Your favourite code editor!

       Last but not least, we need a editor program to write our programs. i will be using visual studio code. Code is a free SW editor developed by Microsoft with open source license. Installation procedure is given below on ubuntu.

• goto –> Code download link
• Download Code.deb package for ubuntu. you also have installer files for other OS’s on the same link.
• Install MS code with below command

  • $ sudo dpkg -i code_1.51.1-1605051630_amd64.deb

• MS code is installed now. Close the terminal.

Let’s write some code, Finally!!!

       Hold your horses, we are not there yet :P Before writing any programs in embedded system, we need to be aware of HW connections we are suppose to sense/control in programs. In our case we need to blink an LED. Let’s take a closer look at the schematics to ascertain which port the LED is connected. As per the below schematic snippet, it is clear that LED is connected to port PB5.

      We have all the necessary information and required tools to control the LED now, It’s time to BLINK the LED :)

blinky C code

      Code snippet below to blink the LED connected to PB5 pin in arduino nano.

#include <avr/io.h>
#include <util/delay.h>

int main(void) 
{
   DDRB |= 1 << PB5;          /* set LED pin PB5 to output */
   while(1) 
   {
     PORTB &= ~(1 << PB5);    /* LED off */
     _delay_ms(900);          /* delay 900 ms */
     PORTB  |= 1 << PB5;      /* LED on */
     _delay_ms(100);          /* delay 100 ms */
   }
   return 0;
}

blinky project make file

      Makefile sample below to build/clean/program the blinky project.

#==== Main Options =============================================================

MCU = atmega328p
F_CPU = 16000000
TARGET = blinky


#==== Compile Options ==========================================================

CFLAGS = -mmcu=$(MCU) -I.
CFLAGS += -DF_CPU=$(F_CPU)UL
CFLAGS += -Os
#CFLAGS += -mint8
#CFLAGS += -mshort-calls
CFLAGS += -funsigned-char
CFLAGS += -funsigned-bitfields
CFLAGS += -fpack-struct
CFLAGS += -fshort-enums
#CFLAGS += -fno-unit-at-a-time
CFLAGS += -Wall
CFLAGS += -Wstrict-prototypes
CFLAGS += -Wundef
#CFLAGS += -Wunreachable-code
#CFLAGS += -Wsign-compare
CFLAGS += -std=gnu99

#==== Programming Options (avrdude) ============================================

AVRDUDE_PROGRAMMER = arduino
AVRDUDE_PORT = /dev/ttyUSB0
AVRDUDE_BAUD = 9600
AVRDUDE_FLAGS = -p $(MCU) -c $(AVRDUDE_PROGRAMMER) -P $(AVRDUDE_PORT)

#===============================================================================
#==== Targets ==================================================================

AVR_GCC_PATH = /usr/bin
CC = $(AVR_GCC_PATH)/avr-gcc
OBJCOPY = $(AVR_GCC_PATH)/avr-objcopy
SIZE = $(AVR_GCC_PATH)/avr-size
NM = $(AVR_GCC_PATH)/avr-nm
AVRDUDE = avrdude
REMOVE = rm -f

all: build

build:
	$(CC) -c $(CFLAGS) $(TARGET).c -o $(TARGET).o
	$(CC) $(CFLAGS) $(TARGET).o --output $(TARGET).elf
	$(OBJCOPY) -O ihex -j .text -j .data $(TARGET).elf $(TARGET).hex
	$(SIZE) -C --mcu=$(MCU) $(TARGET).elf
	#$(NM) $(TARGET).elf

program:
	$(AVRDUDE) $(AVRDUDE_FLAGS) $(AVRDUDE_WRITE_FLASH) -U flash:w:$(TARGET).hex

clean:
	$(REMOVE) "$(TARGET).hex"
	$(REMOVE) "$(TARGET).elf"
	$(REMOVE) "$(TARGET).o"

      The blinky project can be downloaded from our Github repository as always :)

Fruit of our hard work :P

Behold the blinky…… Yay!!!