Blowing Bootloaders into Atmel Chips

A couple of Atmel Chips – the 1284p and the Attiny85 came my way recently – well I say a couple, a few of each – and for the first time I found myself having to program bootloaders for them.

To explain – hobbyists buying the likes of Arduino microcontroller boards generally just have to program “sketches” or programs onto them – and that’s often done with a little serial converter plugged into the USB of their computers. But if you get free samples or come across raw chips not intented for Arduino, they are utterly blank. That is, they don’t have a bootloader – or the minimal code necessary to let you use the serial interface etc.

There are a couple of links here which I’ve used and which work.

http://www.kobakant.at/DIY/?p=3742

The above link lets you program an aTTINY or similar device using an Arduino board (or clone) as a programmer. The Arduino IDE comes complete with a sketch for this – basically blow the sketch onto your Arduino, put a capacitor between reset and ground on the Arduino (to stop it resetting) and then use that Arduino to blow the bootloader onto the Attiny… it’s all in the link – just don’t forget the cap and check your wiring carefully – blowing the bootloader takes seconds. You can then (again without removing the cap) blow sketches onto the little chip – for a test I used the BLINK sketch but changed the output pin to “3” which actually makes physical pin 2 on the chip flash.

The 1284p on the other hand is a different monster – this 40 pin chip has the most RAM of any of the chips while retaining DIP packaging which is ideal for messing around with.  Here’s the link:

http://maniacbug.wordpress.com/2011/11/27/arduino-on-atmega1284p-4/

Similar setup though I don’t recall anything about a capacitor in this case.  One thing you might have issues with the 1284p – is blowing sketches with your serial interface…. if that’s not reliable, I read somewhere that some of the chips have a design issue and that the RX in should have a 10k series resistor – with a 0.1u cap from the RX pin to ground – well, I DID have issues, programming sketches would often stop after a few seconds and that DID fix it for me – I’m happily blowing large sketches into these chips now.

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