Programming ATtiny85 from Arduino Nano - The Bootloader

2022/12/29

Programming ATtiny85 from Arduino Nano - The Bootloader

In the previous blog post in this series, we installed the programmer software on the Nano and placed the last components to be able to program an ATtiny85 chip. New ATtiny85 chips need to be prepared to take Arduino sketches by burning a bootloader. In this post, we go through the steps of configuring the Arduino IDE for programming ATtiny85 and burning the bootloader to ATtiny85.

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Step-by-step Guide

Verify ATtiny85 Placement

Verify the ATtiny85 is installed, according to the design, with pin 1 top right. Check for the notch and the dot at pin 1.

TODO Put macro image here

Connect Nano and Start Arduino GUI

Connect the Nano via USB to your computer for the Arduino GUI to be able to find its COM port. Note the slowly pulsing green LED to indicate the programmer software ArduinoISP.ino is running.

Configure for ATtiny85

We need to set the appropriate settings in the Arduino GUI for programming the ATtiny85. For the purpose of these blog posts, we will leave most settings on their default value.

Select the ATtiny85 Board

Tools -> Board -> ATtiny Microcontrollers -> ATtiny25/45/85

Note that the Tools menu now has additional items, related to the ATtiny:

Clock
Processor

Port

First select the correct COM port.

Tools -> Port -> COM<x>

Verify Board Selection

Make sure you have the correct board selected. It should show ATtiny25/45/85.

Tools -> Get Board Info

BN: ATtiny25/45/85
VID: N/A
PID: N/A

Select OK to close the popup window.

Clock

Tools -> Clock -> Internal 8 MHz

Processor

Tools -> Processor -> ATtiny85

Programmer

Select the programmer for ISP you want to use. You may still have this selected from when it was set in the last blog post.

Tools - Programmer -> Arduino as ISP

Burn the Bootloader

Note that you only have to burn the bootloader once on a newly arrived chip. You have prepared the configuration and can now burn the bootloader.

Tools -> Burn Bootloader

The output window shows the technical details of erasing the chip, installing the bootloader and the verification.

avrdude: Version 6.3-20201216
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch
... detailed info  ...
avrdude: Device signature = 0x1e930b (probably t85)
avrdude: Send: Q [51]   [20] 
avrdude: Recv: . [14] 
avrdude: Recv: . [10] 
avrdude done.  Thank you.

ATtiny85 Prepared

The ATtiny85 is now prepared with the bootloader and is ready to receive sketches. Sketches that work on e.g. Uno, will not automatically work on ATtiny85. They need to be adapted in a process called porting. More on that in the next blog post.