USBtiny

Ever since I first heard about bitbanged USB I knew I wanted to test it.

"USBtiny is a software implementation of the USB low-speed protocol for the Atmel ATtiny microcontrollers." - http://dicks.home.xs4all.nl/avr/usbtiny/

Ladyada has the USBtinyISP based on USBtiny and I decided to hook one up myself. I already got a programmer (sparkfun AVR pocket programmer), but I consider it fun to make my own tools.

It is a great thing LadyAda does by providing schematics and files, so you really should go buy their kit for the programmer instead of doing what I do!

The ATtiny2313 on a breadboard

The first thing I did was to put the ATtiny2313 on a breadboard and write the firmware to it using my existing programmer.

The datasheet for ATtiny2313

avrdude help http://www.ladyada.net/make/usbtinyisp/avrdude.html

The avrdude commands from the Makefile modified to my avrdude.conf location
I just moved to my avrdude folder (D:\daniel\programmering\arduino-1.0.3\hardware\tools\avr\bin) using cmd.exe and ran the command for setting the fuses.

avrdude -c usbtiny -pt2313 -C D:\daniel\programmering\arduino-1.0.3\hardware\tools\avr\etc\avrdude.conf   -U hfuse:w:0xdf:m -U lfuse:w:0xef:m

Where D:\daniel\programmering\arduino-1.0.3\hardware\tools\avr\etc\ is where I have my avrdude.conf.

After setting the fuses its time to write the hex file to the chip:

avrdude -c usbtiny -pt2313 -C D:\daniel\programmering\arduino-1.0.3\hardware\tools\avr\etc\avrdude.conf  -B 1 -U flash:w:main.hex

I actually moved to main.hex file from the  \usbtinyisp\spi folder to the avrdude folder in order for the avrdude to find it.

Then I wired the connections to the USB and tried power it by usb. The LED lights up! Showing us we have USB connection

I use the sparkfun USB pinout

The Ladyada schematics includes a levelconverter that I decided to skip until this circuit gets soldered... Datasheet for the 74HC125. The idea for the level-converter is that the programmer can be powered by usb and the circuit being programmed can be programmed at another voltage level. The level-converter stops the target circuit from being fried.

http://www.ladyada.net/make/usbtinyisp/parts.html

I decided to hook up the attiny8 circuit directly instead.

To the left the ATtiny85V , middle ATtiny2313 and to the right USB level conversions.

In order to know if it works I ran

avrdude -c usbtiny -C D:\daniel\programmering\arduino-1.0.3\hardware\tools\avr\etc\avrdude.conf -p m8

And got:

avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.03s
avrdude: Device signature = 0x1e930b
avrdude: Expected signature for ATMEGA8 is 1E 93 07
         Double check chip, or use -F to override this check.
avrdude done.  Thank you.

...in response! success!

Now I need the board description for the Arduino IDE.

From http://hlt.media.mit.edu/?p=1695 I got the link to
https://github.com/damellis/attiny/archive/master.zip

That I downloaded and copied into the hardware folder. Restarted Arduino IDE and found the ATtiny85 board under boards.

I modified the blink sketch to use pin 2 instead of 13

int led = 2;

Then I uploaded it using programmer (CTRL+SHIFT+U)

Blink sketch on ATtiny85

Very satisfied!!!

I think I will wait until I get a ZIF socket to solder this one up... or at least part of it...