Modified Echo Version 2 - In Production

I am having some issues with the Modela this week. I milled this board last night, but it came out hairy / torn up. I will give it another go tonight.

Download the Board (eagle file):

helloechobutton_07.26.2010.brd

Download the Schematic (eagle file):

Modified Echo Version 1 - Complete But Broken

This version milled out a bit hairy. Some of the traces were broken, so I used jumpers to re-connect them.
There must have been a short somewhere - after stuffing it, setting the fuses and flashing it, I plugged it in to a 9v battery and received a puff of smoke for my efforts. The LED went on - then smoke came out.

In addition, I placed the button too close to the programming header, making it hard to press the button. I am not including the Eagle board or schematic here - see version 2 for a better board.

Back to Eagle!!! See version 2 for a (hopefully) improved and working board).

Fab Academy Module - 06 Embedded Programming

The Assignment

• read an AVR data sheet (ATTtiny 44) - COMPLETE
• make serial and programming cables - COMPLETE
• add (at least) a button to the serial echo hello-world board - See Part II
• modify the serial echo assembly program to respond to the button -See Part II
• modify the serial echo C program to respond to the button -See Part II

The Project: Hello Serial Echo

This hello world board uses a python program (term.py) to send keyboard input over a serial connection from the board to the computer. It is called “serial echo” because when the computer is able to communicate with the board via serial, the python program will allow the keyboard input to be sent to the board and then “echo” it back to the computer. The keyboard input / text will then appear in the python window.

Type the following into the terminal at the prompt:

python term.py /dev/ttyS0 115200

Where “/dev/ttyS0” is the name of the serial port connection to your computer.

When It Is Working - You Should See..

Skills Learned

• I learned how to send data back and forth via a serial connection using Neil’s python program term.py.
• Cable making

Tools Used

• Modela milling machine
• python - term.py
• a computer with a serial connection

Step response board + FTDI + Capacitive sensing

My first step in building this project was to start with the basics. I milled, stuffed and programmed the hello step response board (modified to use the FTDI header by Shawn Wallace). I have a Mac and I can’t troubleshoot / develop at home with the serial header examples.

What You Will See When The Example is Working:

I am using terminal in OS X 10.4.11 - this was the terminal command I used to run the hello step response example and what it will say when it can communicate with the board and begin plotting the graph.

Anna-Kaziunas-Computer:~/Desktop/fab_runs/step annakaziunas$
python hello.step.45.py /dev/tty.usbserial-A600dVDy
finding framing ...
start plotting
0

This is the graph that is displayed:

Here is a screenshot of the charging graph that is produced by Neil’s hello.step.45.py code. This initial charging graph shows the capacitor charging up.

Here is the Capacitive Sensor I Made:

I used thin copper sheets to create the capacitor to test the hello step response board. I hooked them up to jumper wires. When they copper sheets are touching or close to it, the graph will spike up. This indicates that current is flowing through the circuit. When they are far apart the graph will flatten out. This indicates that the circuit is not connected.

For a video of this type of capacitive sensor in action - see the PuppetMaster posts.

The Fab Academy Assignment: make serial and programming cables

Most of the effort in putting the cables together should be directed at figuring out how the pins match up to the wires before attempting to put the cable together.

Headers:

• Use 6-pin headers for the programming cables
• 4 pin headers for everything else (you can use a 6 pin header if you map it correctly, the unused pins will hang off the side of the pins, but that is fine.
• Serial cable header / connector.

The rest of the cable assembly is fairly simple. Using the diagram that you created to match up the pins - thread the wires through the connector, (ensuring they are in the correct pin positions). Then crimp the wires with the connector by pressing down until the header is securely attached.

If you need to split ribbon cable wires into segments in order to map the pins correctly, secure the strands with electrical tape to make it more difficult to pull them out of the header.

The results of Shawn helping me work through the problem of having multiple button with several positions

I'm making a "Persistence of Vision" toy, which will show a programmed message in eight red light- emitting diodes. In the lab we have a roll of copper foil backed with a conductive adhesive. I used a knife to cut out a hand shape. (In this case, I found it faster to work this way than to use the vinyl cutter.) I covered a small metal container with a vinyl sticker to insulate the foil board from the conductive tin. I soldered some surface mount LEDs and resistors onto the copper.

Here is the hand after I drilled holes through the tin and soldered wires to the fingers. The wire on the bottom is ground.

This is the inside of the tin so far!