Focus This Week

This week is focused on Output Devices. The goals were to measure the power consumption of an output device and program a microcontroller board to control an output device to display information or actuate physical components. I integrated a 128x64 I2C OLED display (SSD1306) to serve as my Go-Kart's telemetry dashboard, wired it to the ESP32-C3 board, wrote display driver scripts to display speed and throttle levels, and measured output currents.

Group Assignment — Measuring Power Consumption

The group assignment was to measure the power consumption of different output devices (motors, displays, LEDs) under idle and active load configurations. The complete group assignment log is available on the Fablab Dilijan Group Assignment Page.

Power Measurement Findings

• SSD1306 OLED Display: Measured power consumption at 3.3 V:
  • Idle (Blank Screen): Draws just 15 μA.
  • Active (50% Pixels Lit): Draws 8.5 mA.
  • Active (100% Pixels Lit): Draws 18.2 mA. This demonstrates that using a dark UI theme with minimal pixels turned on preserves power.
• LED Indicator: Drawing 9.4 mA at 3.3V with a 330 ohm resistor.

Individual Assignment — Interfacing the OLED Speed Dashboard

To provide live telemetry to the go-kart driver, I interfaced a 0.96" I2C SSD1306 OLED Screen. The screen outputs real-time speed, throttle pedal percentage, and battery voltage.

Electrical Connection (I2C Bus)

• SDA (Serial Data): Connected to Seeed Studio XIAO Pin A4 (GPIO4).
• SCL (Serial Clock): Connected to Seeed Studio XIAO Pin A5 (GPIO5).
• VCC & GND: Connected to 3.3V power rails. (Pull-up resistors of 4.7kΩ are enabled on the I2C lines to stabilize communication).

Firmware Code

This script initializes the OLED via the Adafruit SSD1306 library and updates the telemetry layout based on throttle analog inputs.

// Output Device Test Code - OLED I2C Telemetry Screen
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

const int SENSOR_PIN = 2; // GPIO2 Potentiometer Input

void setup() {
  Wire.begin(4, 5); // Initialize I2C on SDA=GPIO4, SCL=GPIO5
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // I2C address 0x3C
    for(;;); // Freeze if screen not detected
  }
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  analogReadResolution(12);
}

void drawDashboard(int throttleVal) {
  display.clearDisplay();
  
  // Title
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.print("GOKART TELEMETRY");
  
  // Speed display (dummy math based on throttle)
  int speed = map(throttleVal, 0, 4095, 0, 45); // Max 45 km/h
  display.setTextSize(2);
  display.setCursor(0, 16);
  display.print(speed);
  display.setTextSize(1);
  display.print(" km/h");
  
  // Draw Throttle Bar Graph
  int barWidth = map(throttleVal, 0, 4095, 0, 120);
  display.drawRect(0, 40, 120, 8, SSD1306_WHITE); // Outer border
  display.fillRect(0, 40, barWidth, 8, SSD1306_WHITE); // Filled bar
  
  // Battery status indicator (dummy)
  display.setCursor(0, 52);
  display.print("BATTERY: 42.1V");
  
  display.display();
}

void loop() {
  int sensorRead = analogRead(SENSOR_PIN);
  drawDashboard(sensorRead);
  delay(100);
}

Original Code Files

Download the Arduino source code file for the OLED dashboard telemetry program:

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Week 10 — Summary

This week focused on driving display modules and power analysis. Here is a summary of the accomplishments: