10. Outputs

Overview

This week I worked on my final project in the form of servos. During the week I with the help of ChatGPT was able to control 4 servos which then were put into a looped sequence with the click of a button. Afterwards I designed, milled and soldered a double sided board for the servos to act as a template for my final design.

Group Work

Coding and Servos

Originally, I thought moving four servos at the same time would be easy. My plan was to replicate the servo control code for all four, then tape them to a piece of cardboard to observe the movement. However, I quickly ran into a problem: all the servos moved in the same direction, but since they were positioned facing forward, two of them needed to move in reverse to maintain proper movement. To fix this, I adjusted the code so that the servos on one side moved forward while the others moved backward, keeping everything in sync.

To simplify testing, I added a web server to the Xiao ESP32C3 with a single button that triggers a movement sequence. The sequence begins with two diagonal servos moving first—one transitioning from 90 to 110 degrees and the other from 90 to 70 degrees. This adjustment was necessary because some servos were positioned outward, requiring inverse movements to achieve proper coordination. After the first pair moves, the opposite diagonal pair follows with the same adjustments, creating a stepping motion. The sequence loops continuously when the button is pressed, allowing me to observe and refine the movement without manually restarting the program.

Code

#include <WiFi.h>
#include <ESP32Servo.h>

// WiFi Credentials
const char* WIFI_SSID = "YourWiFiSSID";
const char* WIFI_PASSWORD = "YourWiFiPassword";

// Servo Pins
const int SERVO_PINS[4] = {6, 3, 2, 4}; // GPIO 6, GPIO 3, GPIO 2, GPIO 4

// WiFi Server on port 80
WiFiServer server(80);

// Servo Object Array
Servo servos[4];

// Walking cycle control
bool sequenceRunning = false;
unsigned long lastUpdate = 0;
int sequenceStep = 0;  // Tracks whether we are in step 1 or 2

// HTML Page
const char WEBPAGE[] PROGMEM = R"rawliteral(
<!DOCTYPE html>
<html>
<head>
    <title>ESP32 Servo Control</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <style>
        body { 
            font-family: Arial, sans-serif; 
            max-width: 600px; 
            margin: 0 auto; 
            padding: 20px; 
            background-color: #f4f4f4;
        }
        button {
            padding: 10px;
            background-color: #4CAF50;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
            font-size: 24px;
            width: 100%;
        }
        .arrow {
            font-size: 36px;
        }
    </style>
</head>
<body>
    <h1>ESP32 Servo Control</h1>
    <button onclick="toggleWalkCycle()" class="arrow">→</button>
    <button onclick="sendCommand('reset')">Reset All Servos</button>

    <script>
        function toggleWalkCycle() {
            fetch('/toggleWalkCycle', { method: 'GET' });
        }

        function sendCommand(command) {
            fetch(command, { method: 'GET' });
        }
    </script>
</body>
</html>
)rawliteral";

void setupWiFi() {
    WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
    while (WiFi.status() != WL_CONNECTED) {
        delay(1000);
        Serial.println("Connecting to WiFi...");
    }
    Serial.println("Connected to WiFi");
    Serial.println("IP Address: " + WiFi.localIP().toString());

    // Start the server
    server.begin();
}

void processRequest(String request) {
    if (request.indexOf("toggleWalkCycle") != -1) {
        sequenceRunning = !sequenceRunning; // Toggle walk cycle
    } else if (request.indexOf("reset") != -1) {
        // Reset all servos to 90°
        for (int i = 0; i < 4; i++) {
            servos[i].writeMicroseconds(1500);  // 1500 is 90° for most servos
        }
    }
}

void walkCycle() {
    if (sequenceRunning) {
        unsigned long now = millis();
        if (now - lastUpdate > 100) {  // Adjust delay for walking speed
            lastUpdate = now;

            if (sequenceStep == 0) {
                // Step 1: Move servo 2 and 4 forward to 60°, others stay at 90°
                servos[0].writeMicroseconds(1500); // Servo 6 (90°)
                servos[1].writeMicroseconds(1500); // Servo 3 (90°)
                servos[2].writeMicroseconds(1200); // Servo 2 (Move to 60°)
                servos[3].writeMicroseconds(1200); // Servo 4 (Move to 60°)
            } else if (sequenceStep == 1) {
                // Step 2: Move servo 6 and 3 forward to 120°, others stay at 60°
                servos[0].writeMicroseconds(1200); // Servo 6 (Move to 120°)
                servos[1].writeMicroseconds(1200); // Servo 3 (Move to 120°)
                servos[2].writeMicroseconds(1200); // Servo 2 (Stay at 60°)
                servos[3].writeMicroseconds(1200); // Servo 4 (Stay at 60°)
            } else if (sequenceStep == 2) {
                // Step 3: Reset all servos to 90°
                for (int i = 0; i < 4; i++) {
                    servos[i].writeMicroseconds(1500);  // 90° position
                }
            }

            // Toggle between steps (0 -> 1 -> 2 -> 0 ...)
            sequenceStep = (sequenceStep + 1) % 3; // 3 steps: first side, second side, reset
        }
    }
}

void setup() {
    Serial.begin(115200);

    // Initialize Servos
    for (int i = 0; i < 4; i++) {
        servos[i].attach(SERVO_PINS[i], 500, 2500);  // Adjust to your servo's range
        servos[i].writeMicroseconds(1500);  // Set all servos to 90° (mid position)
    }

    // Setup WiFi
    setupWiFi();
}

void loop() {
    // Listen for incoming clients
    WiFiClient client = server.available();
    if (client) {
        String currentLine = "";
        while (client.connected()) {
            if (client.available()) {
                char c = client.read();
                if (c == '\n') {
                    if (currentLine.length() == 0) {
                        // HTTP headers always start with a response code
                        client.println("HTTP/1.1 200 OK");
                        client.println("Content-type:text/html");
                        client.println();

                        // Send the HTML page
                        client.print(WEBPAGE);
                        break;
                    } else {
                        // Check for specific commands
                        processRequest(currentLine);
                        currentLine = "";
                    }
                } else if (c != '\r') {
                    currentLine += c;
                }
            }
        }
        client.stop();
    }

    // Call walk cycle function if sequence is running
    walkCycle();
}

Explaing it

This code has a lot of moving parts so heres what most of it does

Libraries and Wifi

I used two libaries with them being the wifi and esp32servo. While normally I would need a library for the web server to opitimize it, I didn’t for this one due to its simplicity. The wifi area is just to have the board be able to create the ip adress for a website a device can access if its on the same network.

Servos

The main gist about servos is this. 1) Thier connected to digital pins 2,3,4, and 6 due to complications with digital pin 5.

KiCAD and Double Sided Board

Desigining this board was no easier then coding it since after many crazy person drawings, I realized that I would need to make a double sided board. With the help of Teddy Warrner’s docutmentation on the tools in the lab for making a double sided board, and this KiCAD Tutorial, I was able to learn how to design and mill the PCB.

Overall Concept

  1. When designing the board in KiCAD you can keep the design normal in the ___ but instead of having your wires go to the parts that are going on the bottom of the board go directly to their componets, have them istead connect to a throughhole componet that is then connected to the other componet like a microcontorller or an LED

  2. In the schematic editor, you need to set up the board in a way where the through hole pinouts are near their respective componets but not to close since your drilling all the way through them

  3. To discern the top tracks from the bottom, look to where you normally selcet which type of line your going to make. Normally you would only switch to edge cuts but for the tracks on the bottom, select the option right bellow f_cuts which is b_cuts. F stands for front while B stands for back if that helps.

  4. With this style of line now selceted when you try to connect the throughole pinouts to one another, you won’t run into any collison problems with the f_cut tracks since the software has these new tracks on the other side.

Milling