WEEK 6

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WEEK ·6·

ELECTRONICS DESIGN

INDIVIDUAL ASSIGNMENT

1. redraw the echo hello-world board, 2. add (at least) a button and LED (with current-limiting resistor) 3. check the design rules, make it, and test it extra credit: simulate its operation extra credit: measure its operation

1. USING EAGLE TO RE-DESIGN THE ECHO HELLO WORLD BOARD

To redraw the echo hello-world board I used the Eagle software. It's very easy to download and use. Use the FabLab Library for Eagle, you can download it from here. I started working on schematic view and in the Library menu we searched the Fablab library.

Inside the FabLab library we look for the components and place them one by one in the background screen. (01) ATTINY44-SSU / (01) CAP-US1206FAB / (02) RES-US1206FAB / (01) LEDFAB1206 / (01) 6MM_SWITCH6MM_SWITCH / (01) RESONATOR / (01) FTDI-SMD-HEADER / (01) AVRISPSMD / VCC / GND

To connect the components I recommend to use the "name" option in this way the lines will work as hyperlinks and we will not have as many lines drawn in schematic view. The "label" option is used to display the names placed.

In the menu of schematic view we click on the option "Generate / switch to board" we can visualize the footprints of the components, order them and then place the traces. Use the following settings: Grid: 0.025 " Width: 0.0116 " Clearance: 16 mills

I completed the design but I'm left without connecting two components and having no way to do it. I had to update some things in schematic view

This is the final schematic view.

This is how the board looked like in the end.

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3. USING THE MODELA MACHINE TO MILL THE PCB

I exported the traces and interior drawings in .png format and use the Modela machine to mil and cut the board.

I soldered the components.

Using 02 pins header 2x3 and 30cm of ribbon cable, I assembled the connectors.

I tested with the AVR that the board was running. The green light indicates that the computer recognizes the board.

First was the order to keep the LED on to corroborate that the board would work

Then it was indicated to turn on the LED only when the button was pressed.

And by not pressing the button the LED should be off.

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4. PROGRAMMING

DOWNLOAD FILES

The first thing we did was to check the ports and usb that the computer recognized.

You can program the PCB using the Arduino IDE. For this you'll need the FabISP Programmer and a FTDI cable (5v). In preference copy-paste the URL requested. You'll find it in this link.

Settings to program the PCB Board: "ATtiny” / Processor: "ATtiny44" / Clock: "20MHz (external)" / Programmer: "USBtinyISP"

Then start the Bootloader.

Then we set the output and input acording to our schematic design. The message of Bootloader will appear in the bottom of the page.

Following this tutorial you can see the equivalences.

The number of pins of the ATtiny are not the same in the Arduino.

This picture shows the steps to get the LED on.

And these are the commands we gave to turn the LED on and off if the button is not pressed.

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