1.Schematic and PCB editor in KiCad

I used the schematic editor to create the circuit diagram, it consist four 4-pin vertical headers , that share the then I2C header pins (SDA, SCL, VCC, GND). After that used the PCB editor to place the components and route the traces (with a minimun track with of 1 mm). Once the traces and edge cuts were done, I exported them in Gerber files.

2. Gerber to PNG

I used Gerber2PNG to convert the files into PNG format as it is required by the Mods page. I dowlaoded all the PNG files (drills, traces and outline).

3. Mods Project to RML

I used Mods project to generate the RML toolpaths for the SRM-20, setting x,y,z to 0,0,0 and configuring traces, outline, and drills for each layer.

The settings I use are:

• Traces for the engraving pass: 6º #V-bit tool, 0.4 mm tool diameter, 0.1016 mm cut depth with 4 offsets. And a speed of 4 mm/s.
• Outline (board edge): 1/16 cutout tool, 1.6 mm tool diameter, 0.6096 mm cut depth and a 0.6096 mm max depth. And a speed of 4 mm/s.
• Drills for through-hole: 1/32 drill tool, 0.8 mm tool diameter, 0.254 mm cut depth, 1.7018 mm max depth. And a speed of 0.2 mm/s.

4. Milling on the Roland SRM-20

Once the RML files were generated, I loaded them into the Roland SRM-20 software and set up the milling process. I had to secure the PCB material properly on the milling bed and ensure the each tool was correctly zeroed before starting the milling. The order of milling was: first the dills, then the traces, and finally the outline.

5.Soldering

The fabrication process was simple, I added the pin headers and soldered them one by one.

6. Connecting the components

Once it was soldered, I used jumper wires to connect the RTC and OLED to the hub board and onthe PCB with the XIAO ESP32-C6. The connections are were: SDA to D0 and SCL D1, VCC to 3.3V, and GND to GND.

OLED Welcome Screen (Connection Window)

When the device powers on, the OLED shows a 15-second welcome window displaying the network SSID and the IP address. This gives the user time to connect before the display switches to clock mode. After 15 seconds it transitions automatically to show the current time.

Web Interface

The ESP32-C6 creates its own Wi-Fi network (PillDispenser-MJ) and serves an HTML page at 192.168.4.1. That can be accessed from any phone browser where the user can set a custom alarm time, confirm dose intake, and view a log of recent alarms and doses.

Code Explanation

As shown in the video, the sketch runs four systems simultaneously on the XIAO ESP32-C6: an I2C bus connecting the DS3231 RTC and SH1106 OLED, a Wi-Fi Access Point (PillDispenser-MJ) serving a web interface at 192.168.4.1, an alarm engine that compares UNIX timestamps to trigger dose reminders, and a circular log storing the last 3 alarms set and last 3 doses confirmed. On boot, the OLED shows the network credentials for 15 seconds, then switches to a live clock.

#include <WiFi.h>
#include <WebServer.h>
#include <Wire.h>
#include <RTClib.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SH110X.h>

#define I2C_SDA 0
#define I2C_SCL 1

Adafruit_SH1106G display = Adafruit_SH1106G(128, 64, &Wire, -1);
RTC_DS3231 rtc;
WebServer server(80);

bool isEnglish = true;
DateTime proximaAlarma;
bool pastillaPendiente = false;
unsigned long startTime = 0;

struct LogEntry {
  char hora[9];
  bool activo = false;
};
LogEntry logAlarmas[3];
LogEntry logDosis[3];
int idxA = 0, idxD = 0;

void agregarLogAlarma(String h) {
  strncpy(logAlarmas[idxA].hora, h.c_str(), 8);
  logAlarmas[idxA].activo = true;
  idxA = (idxA + 1) % 3;
}

void agregarLogDosis(String h) {
  strncpy(logDosis[idxD].hora, h.c_str(), 8);
  logDosis[idxD].activo = true;
  idxD = (idxD + 1) % 3;
}

void handleSetAlarm() {
  String t = server.arg("atime");
  if (t != "") {
    int h = t.substring(0,2).toInt();
    int m = t.substring(3,5).toInt();
    DateTime now = rtc.now();
    proximaAlarma = DateTime(now.year(), now.month(), now.day(), h, m, 0);
    if (proximaAlarma.unixtime() <= now.unixtime()) {
      proximaAlarma = proximaAlarma + TimeSpan(1, 0, 0, 0);
    }
    pastillaPendiente = false;
    agregarLogAlarma(t);
  }
  server.sendHeader("Location", "/");
  server.send(303);
}

void handleTomada() {
  pastillaPendiente = false;
  DateTime now = rtc.now();
  char buf[10]; sprintf(buf, "%02d:%02d", now.hour(), now.minute());
  agregarLogDosis(String(buf));
  proximaAlarma = now + TimeSpan(0, 8, 0, 0);
  server.sendHeader("Location", "/");
  server.send(303);
}

void handleToggleLang() { isEnglish = !isEnglish; server.sendHeader("Location", "/"); server.send(303); }

void handleReset() {
  pastillaPendiente = false;
  proximaAlarma = DateTime((uint32_t)0);
  for(int i=0; i<3; i++) { logAlarmas[i].activo = false; logDosis[i].activo = false; }
  server.sendHeader("Location", "/");
  server.send(303);
}

void setup() {
  Wire.begin(I2C_SDA, I2C_SCL);
  display.begin(0x3C, true);
  display.setRotation(2);
  rtc.begin();
  rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  WiFi.softAP("PillDispenser-MJ", "fabacademy");
  server.on("/", handleRoot);
  server.on("/tomada", handleTomada);
  server.on("/toggleLang", handleToggleLang);
  server.on("/setAlarm", handleSetAlarm);
  server.on("/reset", handleReset);
  server.begin();
  startTime = millis();
}

void loop() {
  server.handleClient();
  DateTime now = rtc.now();
  if (proximaAlarma.unixtime() > 0 && now.unixtime() >= proximaAlarma.unixtime() && !pastillaPendiente) {
    pastillaPendiente = true;
  }
  static unsigned long lastDisp = 0;
  if (millis() - lastDisp >= 500) {
    display.clearDisplay();
    display.setTextColor(SH110X_WHITE);
    display.display();
    lastDisp = millis();
  }
}

The web interface supports English/Spanish toggle, quick and custom alarm presets, dose confirmation, and a full reset all without reloading the page. The code was made with help of Claude, and was a combination of trial and error, debugging, and iterative development, starting from basic I2C communication, then adding the web server, and finally integrating all features together.

Example of early web interface

This was one of the first iterations of the web interface, showing the basic layout and functionality before the final design was implemented.

Demo Video

The following video shows the full system running: the XIAO ESP32-C6 creates a Wi-Fi access point, the OLED displays the clock and alarm notifications, and the web interface is used from a phone to set an alarm and confirm a dose.