14. November 2022

Output Devices

This week’s assignment was to add an output device to a microcontroller board.

Design

I decided to use the capacitive touch sensor I designed last week to control an RGB LED. As such, I redesigned my board from last week to include the RGB LED; I made sure to have the cathodes of the LED connect to PWM pins of the microcontroller.

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I then routed the paths in a similar fashion to my other board.

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Milling

After designing my board, I milled it.

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Stuffing

I then stuffed my board; shown are my board from this week, as well as the parts I made last week.

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I added a connector to the VCC of the serial-UPDI board so I could supply power and program my boards from my own computer.

Programming

Finally, I programmed my board so that the LED is

Blue when the sensor is pressed too gently
Green when the sensor is pressed with just the right amount of force
Red when the sensor is pressed too hard

 1#define analog_pin PIN_PA4
 2#define tx_pin PIN_PA5
 3#define red_pin PIN_PB1
 4#define green_pin PIN_PB0
 5#define blue_pin PIN_PA3
 6int red_thresh = 6000;
 7int green_thresh = 7500;
 8int blue_thresh = 9000;
 9
10long result; 
11
12void setup() {
13    pinMode(tx_pin,OUTPUT);    
14    Serial.begin(9600);
15
16    pinMode(red_pin,OUTPUT);
17    pinMode(green_pin,OUTPUT);
18    pinMode(blue_pin,OUTPUT);
19
20    digitalWrite(red_pin,HIGH);
21    digitalWrite(green_pin,HIGH);
22    digitalWrite(blue_pin,HIGH);
23}
24
25long tx_rx(){         
26    int read_high;
27    int read_low;
28    int diff;
29    long int sum;
30    int N_samples = 100;  
31
32    sum = 0;
33    for (int i = 0; i < N_samples; i++){
34    digitalWrite(tx_pin,HIGH);              
35    read_high = analogRead(analog_pin);        
36    delayMicroseconds(100);            
37    digitalWrite(tx_pin,LOW);               
38    read_low = analogRead(analog_pin);        
39    diff = read_high - read_low;    
40    sum += diff;             
41}
42    return sum;
43}                         
44
45void loop() {
46    result = tx_rx();
47    if (result < red_thresh) {
48        digitalWrite(red_pin,LOW);
49        digitalWrite(green_pin,HIGH);
50        digitalWrite(blue_pin,HIGH);
51    } else if (result < green_thresh) {
52        digitalWrite(green_pin,LOW);
53        digitalWrite(blue_pin,HIGH);
54        digitalWrite(red_pin,HIGH);
55    } else if (result < blue_thresh){
56        digitalWrite(blue_pin,LOW);
57        digitalWrite(red_pin,HIGH);
58        digitalWrite(green_pin,HIGH);
59    }
60    Serial.println(result);
61    //delay(100);
62}

Overall, the input and output devices work very well!

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