redraw the echo hello-world board

This week’s lesson is to redraw the hello-world board. What I got is the CAD file and some pcb graph. I have played with eagle for some time, so I decided to to use Eagle to finish this homework.

I download the eagle software from cadsoftusa site. There are different platform for Windows, Unix and Mac. You can use it for trial (30 days) or free (non commercial use only). For fab users, 10cm*10cm size and 2 layers of PCB limitation of free use is not a big problem, because our assignment is only require one layer, for most of the task, two layers is OK.

Eagle library

For fablab we have fab.lbr file. Just copy the fab.lbr file to the eagle’s lbr directory. You may need to use fab.lbr from the control panel manually if not. There are more commonly used lib file can be obtained from Adafruit and sparkfun. Here is the link:

Adafruit Eagle Lib files
Sparkfun Eagle Lib files

Also you can change the eagle’s library settings, add a path to the library files.

Prepare the PCB

The original hello.ftdi.44.png are here. To add a button and a LED, we need to redraw the schematic file first. I googled some simple schematic file for reference. The main part is attiny84, to make it running, we need to add VCC, GND, capacitors, resistors, and resonator, a button and a led to get it work.

Add a button and LED

Finally I got a sch like this. I connect LED to PA7 and BUTTON to PA3, let the button input to stay high.

I want to use autorouter fuction to finish the work, I had never tried a single pcb layer before. I change the layer 16 to N/A, and pressed the autorouter button, to my surprise, I got a single layer pcb file.

I change the global setting, setting the clearance all to 12mil (0.3mm), which can make sure the copper lines are not to closely.

It is not look very terse like the original one, so I decide to manual route it. So I made some change to the schematic file, change to port of button and led, and using internal pull up function of attiny85, the modified schematic looks like

and the manual routed pcb is more beautiful.

extra credit: simulate its operation

I just noticed eagle 7.5 has the simulation function. It’s worth to have a try.

Kicad Fab lib files

In this week, I converted the fab.lbr file to kicad format using eagle’s plugin, and I’d like to share it.

Here is the download link: Kicad fab lbr