From stereo to visuals

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This week, we were set with the task of building an output device; class notes are here. I wanted to start tackling elements of my final project of building an EEG. Since the EEG will involve inputting voltage from the leads coming from a user's head and the output will be sounds or graphs based on the signal, I played with a few designs. One idea was to combine the speaker board from this week and the microphone for next week's input assignment. The other idea was to figure out how I would visualize my signal in my EEG project. For the first idea - a combined speaker and microphone board - I used the speaker board: http://academy.cba.mit.edu/classes/output_devices/speaker/hello.speaker.45.png and the microphone board: http://academy.cba.mit.edu/classes/input_devices/mic/hello.mic.45.png. In order to optimally combine the input and output week, I decided to create an optimized board that pulled the relevant prats of the speaker board and the microphone. First, I modified the stereo output design by only including input power and the 5 volt regulator (preventing voltage from going higher than 5v), but deleting the t45 and the isp. I used pb0 or pb1, and I decided to use the hardware to change the pwm frequency. Ultimately, though, I decided not to go this route. A few reasons: the number of components involved in this design was higher than I want for my final project (I'm aiming for under 15). So, I decided to start the spiral design cycle for my EEG project. Ultimately, I realized that I wanted to use the simple .

Since I'll use Audacity and Physics Oscilloscope for the first part of my spiral development in the final project, but they obfuscate how they do the visualization, I found a description for how to visualize a signal coming in from Chipstein's site an Arduino based EEG set up and spent a lot of time understanding it.

// SET FOR 5 SECONDS EEG, 180 Hz. A LONGER DISPLAY MAY RUN SLOW, // DEPENDING ON THE SPEED OF YOUR CPU. import processing.serial.*; Serial port; // Create object from Serial class int val; // Data received from the serial port int cnt; int hht; int wm1; int[] values; void setup() { size(900, 400); //currently set to 5 sec // Open the port that the board is connected to and use the same speed (19200 bps) port = new Serial(this, Serial.list()[0], 19200); values = new int[width]; hht = 750; // Sets display DC offset; must adjust if gain is changed# wm1= width-1; cnt = 1; frameRate(180); //read/draw 180 samples/sec for (int s=0;s= 3) { //read the latest value if (port.read() == 0xff) { val = (port.read() << 8) | (port.read()); } } values[cnt] = val; //put it in the array# cnt++; //increment the count stroke(60); for (int d = 0; d < width-1; d = d + 180) { //**draw lines for seconds line(d,0,d,400); } stroke(255,255,0); line(cnt,100,cnt,300); //draw the leading edge line stroke(255,0,0); for (int x=2; x wm1) { //back to beginning cnt = 1; } }

With the above code, you get pretty EEG recordings. I'm not going to post them here, because I did not verify them with a homemade Arduino set up of my own, but you can see them here.

Another area for comparison in trying to understand the broader question of oscilloscopes is in Processing. It is at http://accrochages.drone.ws/sites/accrochages.drone.ws/files/Oscilloscope.pde: That code is under a GNU Public License. It expects port 0 to be the origin of the Arduino signal.

import processing.serial.*; Serial port; // Create object from Serial class int val; // Data received from the serial port int[] values; void setup() { size(640, 480); // Open the port that the board is connected to and use the same speed (9600 bps) port = new Serial(this, Serial.list()[0], 9600); values = new int[width]; smooth(); } int getY(int val) { return (int)(val / 1023.0f * height) - 1; } void draw() { while (port.available() >= 3) { if (port.read() == 0xff) { val = (port.read() << 8) | (port.read()); } } for (int i=0; i> 8) & 0xff, BYTE); Serial.print( val & 0xff, BYTE); } */