<br>
#### The Inspiration:
<img src="/ps70/ledcube.gif" alt="led-gif">
Charlieplexing: A way to use N I/O pins to control N(N-1) LEDs
#### Controlling 6 LEDs
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<img src="/ps70/charlie_schem.png" class="img-responsive" style="width:100%" alt="Image"></a>
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<img src="/ps70/6led.png" class="img-responsive" style="width:100%" alt="Image"></a>
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Though the inspiration came from the LED cube shown above, I knew this wouldn't be a good place to start. To start, I wanted to make a basic charlieplexing setup using 3 I/O pins and 6 LEDs. I followed <a href="https://www.instructables.com/Charlieplexing-the-Arduino/">this instructable</a> to set up my first circuit, but ran into issues getting every LED to light up. It turns out the given schematic was wrong, but once I added a missing wire, the LED's all lit up using test code!
Materials for setting up the circuit:
1. 6x LEDs
2. Breadboard
3. ESP32 S2 Dev Board
4. Wires
5. 3x 1k Ohm Resisters
I then adapted the test code given on the instructables site to add more capability to the LEDs. First, I labeled each LED on the breadboard with a number (1, 2, ..., 6), and created functions that would turn on each LED. These functions would simply vary the pinMode of each I/O pin and write either a LOW or HIGH signal to these pins. I then wrote functions that would create specific patterns within the 6 LEDs, using the individual LED functions.
Current Functions:
1. void in_order(): turns on the LEDs in order
2. void circular(): turns on LEDs one by one in a circular pattern
3. void two_at_a_time(): turns on LEDs two at a time, by oscillating two LED's on and off very quickly
4. void stay_lit(): attempting to turn the LEDs on in order, without turning any LED that's been turned on back off
#### Code:
Below is the current form of my code - to be modified and improved for more LEDs and more patterns!
<pre><code>
// define LED pins
const int LED_1 = 11; //LED row 1
const int LED_2 = 13; //LED row 2
const int LED_3 = 12; //LED row 3
// define piezo input
const int piezoSensor = 2;
const int threshold = 100;
int sensorReading = 0;
void led1() {
//turn on LED L1
pinMode(LED_1, OUTPUT); //row 1
digitalWrite(LED_1, LOW);
pinMode(LED_2, OUTPUT); //row 2
digitalWrite(LED_2, HIGH);
pinMode(LED_3, INPUT); //row 3
digitalWrite(LED_3, LOW);
}
void led2() {
//turn on LED L2
pinMode(LED_1, OUTPUT); //row 1
digitalWrite(LED_1, HIGH);
pinMode(LED_2, OUTPUT); //row 2
digitalWrite(LED_2, LOW);
pinMode(LED_3, INPUT); //row 3
digitalWrite(LED_3, LOW);
}
void led3() {
//turn on LED L3
pinMode(LED_1, INPUT); //row 1
digitalWrite(LED_1, LOW);
pinMode(LED_2, OUTPUT); //row 2
digitalWrite(LED_2, LOW);
pinMode(LED_3, OUTPUT); //row 3
digitalWrite(LED_3, HIGH);
}
void led4() {
//turn on LED L4
pinMode(LED_1, INPUT); //row 1
digitalWrite(LED_1, LOW);
pinMode(LED_2, OUTPUT); //row 2
digitalWrite(LED_2, HIGH);
pinMode(LED_3, OUTPUT); //row 3
digitalWrite(LED_3, LOW);
}
void led5() {
//turn on LED L5
pinMode(LED_1, OUTPUT);
digitalWrite(LED_1, HIGH);
pinMode(LED_2, INPUT);
digitalWrite(LED_2, LOW);
pinMode(LED_3, OUTPUT);
digitalWrite(LED_3, LOW);
}
void led6() {
//turn on LED L6
pinMode(LED_1, OUTPUT); //row 1
digitalWrite(LED_1, LOW);
pinMode(LED_2, INPUT); //row 2
digitalWrite(LED_2, LOW);
pinMode(LED_3, OUTPUT); //row3
digitalWrite(LED_3, HIGH);
}
void in_order() {
led1();
delay(100);
led2();
delay(100);
led3();
delay(100);
led4();
delay(100);
led5();
delay(100);
led6();
delay(100);
}
void circular() {
led1();
delay(100);
led3();
delay(100);
led5();
delay(100);
led6();
delay(100);
led4();
delay(100);
led2();
delay(100);
}
void two_at_a_time() {
for (int i = 1; i < 5000; i = i+1) {
led1();
led2();
//delay(1);
}
for (int i = 1; i < 5000; i = i+1) {
led3();
led4();
//delay(1);
}
for (int i = 1; i < 5000; i = i+1) {
led5();
led6();
//delay(1);
}
}
void stay_lit() {
for (int i = 1; i < 5000; i = i+1) {
led1();
//delay(1);
}
for (int i = 1; i < 5000; i = i+1) {
led1();
led3();
//delay(1);
}
for (int i = 1; i < 5000; i = i+1) {
led1();
led3();
led5();
//delay(1);
}
for (int i = 1; i < 5000; i = i+1) {
led1();
led3();
led5();
led6();
//delay(1);
}
for (int i = 1; i < 5000; i = i+1) {
led1();
led3();
led5();
led6();
led4();
//delay(1);
}
for (int i = 1; i < 5000; i = i+1) {
led1();
led3();
led5();
led6();
led4();
led2();
//delay(1);
}
}
void setup()
{
Serial.begin(9600);
}
void loop()
{
// I want to try to incorporate a piezo sensor to have the LED array "react" to knocking, but I haven't worked it out yet
sensorReading = analogRead(piezoSensor);
Serial.println(sensorReading);
// call a function for some sort of LED pattern
circular();
}
</code></pre>
#### Preliminary Demos:
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<video width="200" controls autoplay>
<source src="/ps70/circular.mov" type="video/mp4">
</video>
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<video width="200" controls autoplay>
<source src="/ps70/two_at_once.mov" type="video/mp4">
</video>
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<video width="200" controls autoplay>
<source src="/ps70/staylit.mov" type="video/mp4">
</video>
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Preliminary demos show success in creating the in_order, circular, and two_at_a_time patterns on the LEDs. However, the stay_lit() function did not work very well, and was the first large problem that I ran into through the code. This was an indicator that the way I am coding these LEDs programs as a whole is probably quite inefficient and suboptimal.
As part of my next steps, I'd love to figure out a new way of creating software for using charlieplexed LEDs. One possible route is rather than creating individual functions for each LED to turn on, I could create one matrix that stores the pinMode and digitalWrite values that correspond to each LED turning on. This way, the matrix could be referenced in a specific way for each LED to turn on.