Microcontroller: AVR ATtiny85

2019-12-06

About

This documentation gives a kind of microcontroller programming from scratch. I used the ATtiny85 for this example. IMHO its simplest, smallest, ... and a good starting point. The aim was:

• Code a programm (preferable in C) and run it on the uC.
• The wiring, powering, is all done manually.
• No ready-to-use embedded single boards, or other comfortable chips, sticks.

Tools

Used tools in this doc.

• dmesg: list kernel ring buffer
• lsusb: list usb devices
• avrdude: for programmer, transfer code from computer to microcontroller
• gcc-avr: compiler for AVR
• avr-libc: AVR C library
• optional tools
  • binutils-avr: tools like assembler, linker
  • gdb-avr: debugger for

Example: main.c

#define F_CPU 8000000UL

#include <avr/io.h>
// /usr/lib/avr/include/avr/iotn85.h
#include <util/delay.h>

/*
led the LED blink each 500ms
*/
int main (void) {

   DDRB |= (1 << PB0);

   while(1) {
       PORTB ^= (1 << PB0);
       _delay_ms(500);
   }

   return 0;
}

• Step 1: we need to bring our program to uC (microcontroller)
• Step 2: run the uC

Step 1: compile, build and flash

In order to bring our program to the uC we need a elf format. To be short. These are the steps for it:

avr-gcc -mmcu=attiny85 -Os -c main.c  -o main.o
avr-gcc main.o -o main.elf
avr-objcopy -O ihex -j .text -j .data main.elf main.hex
avr-size --mcu=attiny85 -C main.elf 
avrdude -p attiny85 -c usbasp -U flash:w:main.hex:a

The connection between the computer and microcontroller is done with a programmer. In my case its a USBasp. For more: https://fischl.de/.

Usually the USBasp will have a ISP 10 pin cable witch is wired to the relevant pins in ATtiny85.

AVRISP mkII is also a good choice. It's just hard to find a original one and its expensive. You also have to extra power you uC.

Step 2: running

After flashing process the program is loaded into the ATtiny85. Wire a circuit with a led to PIN 5 on ATtiny85 and power it up.

circuit

• the led will glow every 500ms with flashed main.c example

cheatsheet

• list supported uController: avrdude -p?
• check connection between programmer (e.g. USBasp, AVRISP, ...):

avrdude -p attiny85 -c usbasp

or

avrdude -p t85 -c usbasp

electricity

• power-bus in breadboard (+ and - lines)
• red cable is +
• black cable is -
• integrated circuit (IC) = chips comes with DIP (dual in-line package) for the middle gab in breadboard

Atmel ATTiny85

Reset   1   8   VCC (5V)
        2   7	SCK
        3   6	MISO
GND     4   5	MOSI

Serial Peripheral Interface

• SCK: Serial Clock
• MOSI: Master Output Slave Input
• MISO: Master Input Slace Output

USB to TTL Serialadapter

• check connection with dmesg
• connect with minicom
• convert TTL logic to RS232
• USB serial converter

ISP AVR

• 10 or 6 pins
• In System Programming
• use with: avrdude -p attiny85 -c avrispmkII

Repository

• https://github.com/leventarican/microcontroller