Microcontroller development system

1.Design Description	Use AVR Tiny15L, which is a low-power CMOS 8-bit RISC microcontroller, to build up a hello world application. The parellal port sends out machine codes which are stored in flash memory of the microcontroller. The serial port listens to the output of Tiny15L.
2.Schematics
3.Layout
4.Some remaining questions	1. About microcontroller: generally, how to design the circuit using microcontroller? how complex programs can Tiny15L run? 2. About Eagle: how to build our own library file?
5.Trouble Shooting----how to build your own library	if you can find out any schematics provided by the manufacturer, your life will be much easier. However, the life is not always that good. The following steps help you out if you are a little bit unlucky this time. 1. Find out the sizes of the package you want to use, usually you can find them in datasheet. 2. Draw the package with exactly right width, length, right pins and clearance between pins... all that kinds of stuff. Be very careful or real chip will not fit on your board. You can do that yourself if you are really talent in drawing and have a plenty of time, otherwise an easier way is to find out an existing package similar enough to your desired one. Usually you can find them in eagle library "smd-ipc.lbr". For example, your chip package is something like SO14 with 14-pin, 5mm width. 3. open the package of SO14 in library "smd-ipc.lbr". Cut it and paste it in a new library "package" you want to creat. 4. open "schematics" of new library, then draw something rectangle and looking nice. then put on 14 pins. Click "name" on the left pannel, and name all the pins such as Vcc, Gnd, Input etc according to the datasheet. 5. open "device" of new library. Firstly instantiate your schematics, the button is on the left pannel. And then press "new" on your right hand side pannel, choose the package you just created. Now you need to "connect" the pins in schematics with those in packages. After this mapping is done, congratulations your library has been built! don't forget to save your work. 6. "file->new" a schematic. in "library->use" enjoy using your own library.