Embedded Systems / IoT / Financial Data Display

Gold & Silver Price Tracker

Gold & Silver Price Tracker (internally titled "MetalsTracker") is a real-time precious metals price display device built for the LilyGO ESP32-S3 h...

Gold & Silver Price Tracker

Category: Embedded Systems / IoT / Financial Data Display
Platform: LilyGO T-Display-S3 / LilyGO T-Deck Plus / LilyGO T-Dongle S3 (ESP32-S3)
Framework: Arduino via PlatformIO | C++
Status: Active — Production Ready (v2)

Project Overview

Gold & Silver Price Tracker (internally titled "MetalsTracker") is a real-time precious metals price display device built for the LilyGO ESP32-S3 hardware family. It fetches live gold (XAU) and silver (XAG) spot prices denominated in Australian Dollars (AUD) from the MetalPriceAPI, and renders them on a purpose-built graphical dashboard with gradient panels, animated rainbow dividers, and custom metallic icons.

The device is engineered for reliability and efficiency — it only wakes the WiFi radio every 12 hours to refresh prices, then immediately disconnects and renders the updated data locally. A hardware button provides on-demand manual refresh at any time. The result is a beautifully styled, always-visible precious metals ticker that runs virtually indefinitely on a battery.

Core Features

Live Price Data

  • Fetches gold (XAU) and silver (XAG) spot prices via HTTPS from MetalPriceAPI
  • Prices returned as exchange rates relative to AUD (XAU/AUD, XAG/AUD) and inverted to produce the AUD price per troy ounce
  • Data displayed as formatted price strings: e.g., $4,523.81 AUD
  • Currency formatting uses the AsciiFont8x16 glyph set which correctly renders $ (unlike TFT_eSPI's Font4 which maps $ to £)

Smart WiFi Power Management

  • 12-hour auto-refresh cycle — WiFi is activated, data fetched, NTP synced, and WiFi disconnected — all within a single fetch cycle
  • Between refreshes, the device runs fully offline — no background radio activity
  • WiFiManager handles first-time setup via a captive portal (AP name: MetalsTracker-Setup)
  • Saved WiFi credentials are cached in memory and reused for each 12-hour reconnect

On-Demand Manual Refresh

  • BOOT button (GPIO 0) interrupt-driven at hardware level (IRAM_ATTR ISR)
  • Hold BOOT for 500ms to trigger an immediate full refresh cycle
  • Debounced via interrupt state tracking — prevents false triggers

Animated Loading Screen

  • Custom "FETCHING NEW DATA..." loading screen displayed during each refresh
  • Features a 12-frame rainbow spinner animation (8 HSV-coloured orbiting dots)
  • Spinner runs for approximately 1.2 seconds before API call begins

Graphical Dashboard Layout

The dashboard is divided into five precisely calculated sections across a 320x170 landscape display:

Section Y Position Height Content
Header 0 18px Title, WiFi status icon, current time
Gold Panel 18 62px Gold bar icon, XAU label, price
Rainbow Divider 80 8px Full-width HSV colour sweep
Silver Panel 88 62px Silver coin icon, XAG label, price
Footer 150 20px Countdown to next refresh, button hint

Premium Visual Design

  • Gold Panel: Warm dark amber to near-black gradient background; 28x14px gold bar icon with sheen, shadow, and centre groove detail
  • Silver Panel: Cool slate gradient background; silver coin icon with highlight and dimensional rendering
  • Rainbow Divider: Full-width HSV sweep at full saturation — cycles through the complete visible spectrum
  • WiFi Status Icon: 4-bar signal strength icon (green when connected, red when offline)
  • Header: Dark navy background with metallic accent text and cyan timestamp
  • Footer: Countdown timer (Xh YYm) updating every 5 seconds; button hint text

First-Run WiFi Setup Screen

  • Custom on-device setup instructions displayed while WiFiManager captive portal is active
  • Styled instruction box with step-by-step numbered guide
  • AP name highlighted in cyan, browser URL in green
  • Rainbow bar at bottom for visual flair

NTP Time Synchronisation

  • Syncs to pool.ntp.org on every 12-hour refresh cycle
  • AEST/AEDT timezone (Australian Eastern Time with DST support)
  • Time displayed in 12-hour format (H:MM AM/PM) in the dashboard header
  • Header time refreshes every 60 seconds independently of the data refresh

Multi-Board Support

The project supports three LilyGO hardware variants with separate build environments:

Board Environment Display Interface Notes
T-Display S3 lilygo-t-display-s3 8-bit parallel i8080 320x170 ST7789
T-Deck Plus tdeck-plus SPI ST7789 320x240 with keyboard
T-Dongle S3 tdongle-s3 Custom Compact dongle form factor

Each board has its own source file and build filter in platformio.ini:

  • main.cpp — T-Display S3
  • main_tdeck.cpp — T-Deck Plus
  • main_tdongle.cpp — T-Dongle S3

Technical Architecture

Component Detail
MCU ESP32-S3 @ 240 MHz
Display ST7789 1.9" IPS — 320x170 (i8080 8-bit parallel)
Graphics Library LovyanGFX v1.2 — native i8080 bus driver
WiFi WiFiManager v2.0 — captive portal + credentials cache
HTTPS WiFiClientSecure (setInsecure — no cert pinning)
JSON ArduinoJson v7.0 — streaming deserialization
RTOS FreeRTOS (vTaskDelay for non-blocking sleep)
Time configTzTime — POSIX timezone string (AEST-10AEDT)
Button ISR GPIO 0 CHANGE interrupt with IRAM_ATTR handler

API Integration

Service Purpose Endpoint
MetalPriceAPI Live XAU/XAG spot prices in AUD api.metalpriceapi.com/v1/latest

API returns base=AUD with currencies=XAU,XAG. The device computes:

  • Gold AUD = 1.0 / XAU_rate
  • Silver AUD = 1.0 / XAG_rate

Colour System

All colours are initialised after display setup using tft.color565():

Token Use Case RGB Approximate
C_GOLD Gold text and primary gold elements #FFD200
C_GOLD_DIM Gold icon shadows and borders #5A4100
C_GOLD_BRIGHT Gold icon sheen highlights #FFF88C
C_SILVER Silver text and primary silver elements #C3CAD7
C_SILV_DIM Silver icon shadows #4B505F
C_SILV_BRIGHT Silver coin highlight #EBF2FF
C_HDR_BG Header background #0C0C1C
C_WIFI_OK WiFi connected indicator #00D74B
C_WIFI_ERR WiFi error indicator #F03232

Deployment

  1. Open project in PlatformIO
  2. Select environment matching your hardware (lilygo-t-display-s3, tdeck-plus, or tdongle-s3)
  3. Build and flash to device
  4. On first boot: connect phone to MetalsTracker-Setup WiFi hotspot
  5. Open browser at 192.168.4.1 and enter home WiFi credentials
  6. Device connects, syncs NTP, fetches first prices, and renders the dashboard
  7. Hold BOOT button (500ms) at any time to force an immediate price refresh
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