Built-in USBtiny ISP
OpenSprinkler v1.2u and above have built-in USBtiny ISP programmer implemented using an ATtiny45 chip. USBtiny is one among many choices to directly program an AVR microcontroller, without the need of a bootloader. It is already supported by Arduino software. There are many implementations of USBtiny, notably Lady Ada’s USBtinyisp and SparkFun’s pocket AVR programmer. OpenSprinkler adopts the ATtiny45 implementation because it requires minimal components: one ATtiny45 and three resistors, that’s all. It makes use of ATtiny45’s internal PLL to avoid any external oscillator. In addition, OpenSprinkler uses slightly modified USBtiny code to maximize the data transfer speed.
Is your modified ATtiny45 code available for download? I am building a 1.02 board from scratch and have blank chips.
You mean OpenSprinkler Pi 1.02? That does not use a microcontroller, so I don’t know why you need the code for ATtiny45. But in any case, I have checked in the source code to Github. Here is the subfolder that contains the code:
https://github.com/rayshobby/opensprinkler/tree/master/OpenSprinkler%20Controller/software/vusbtiny
Sorry, typo. I meant 1.2u March 2012 board which I just finished today and it works great! Thanks for posting the ATtiny USB code!!