An ESP32-based desk gadget that shows the live Bitcoin price and the local time, alternating on an 8‑digit MAX7219 seven‑segment display. It is fully configurable from a built‑in web page, keeps an on‑device price history graph, and can trigger a wake‑up alarm on a Sonos speaker through Home Assistant (MQTT).
This is the ESP32 port of the original ESP8266 project. A matching 3D‑printed "Bitcoin character" enclosure is available on Thingiverse.
- Live Bitcoin price in USD or EUR, fetched from Coinbase (no account / no API key required).
- NTP clock with automatic daylight‑saving handling via a timezone picker.
- Alternating display of price and time, with a configurable switch interval.
- Web interface (dark theme by default) to configure and monitor everything:
- Live price, clock and alarm status.
- Persistent price chart built from on‑device history (one sample every 15 minutes).
- MQTT broker configuration.
- Alarm time + enable toggle.
- Brightness slider (0–15).
- General settings: currency, timezone, toggle interval, MQTT topic.
- WiFi reset button and firmware version display.
- Wake‑up alarm: at the configured time the device publishes an MQTT message that a Home Assistant automation uses to play a track on a Sonos speaker.
- WiFiManager captive portal — no WiFi credentials hard‑coded in the firmware.
- OTA updates through ElegantOTA (upload a new firmware from the browser).
- Settings persisted in flash (NVS) — they survive reboots.
- Hardware: migrated from the Wemos D1 mini (ESP8266) to an ESP32 (more RAM, far more reliable HTTPS — no more long‑uptime TLS lock‑ups).
- Price source: switched from CoinGecko to Coinbase, because CoinGecko's free API now enforces tight rate limits / requires an API key. Coinbase's spot endpoint is keyless and account‑free.
- TLS: BearSSL →
WiFiClientSecure(mbedTLS). - Time:
NTPClient→ built‑in SNTP with a POSIX timezone string and a friendly timezone dropdown (automatic DST). - Storage: SPIFFS + JSON →
Preferences(NVS). - OTA: hand‑written upload handler → ElegantOTA.
- Non‑blocking price fetch: the display and web UI stay responsive even when the network is slow or down.
- New UI features: currency selector (USD/EUR), persistent price chart, configurable settings, alarm status on the main page, brightness slider, WiFi reset, firmware version.
Current firmware version: 2.1.0.
- ESP32 development board (ESP‑WROOM‑32; a D1‑mini form‑factor board works well)
- MAX7219 8‑digit 7‑segment display module
- A few jumper wires
- USB power (the display is powered from the board's 5 V rail)
- (Optional) 3D‑printed Bitcoin enclosure (see Thingiverse link above)
| MAX7219 | ESP32 |
|---|---|
| DIN | GPIO23 |
| CLK | GPIO18 |
| CS / LOAD | GPIO19 |
| VCC | 5V (the board's VCC pin) |
| GND | GND |
The ESP32 drives the data lines at 3.3 V logic while the MAX7219 is powered at 5 V — this works reliably (it is the same arrangement as on the ESP8266). The pins are bit‑banged, so you can change them in the sketch if needed (avoid input‑only pins 34–39, the flash pins, and strapping pins).
Install via the Arduino IDE Library Manager:
- WiFiManager (by tzapu)
- ArduinoJson (v7.x)
- LedControl (by Eberhard Fahle)
- PubSubClient (by Nick O'Leary)
- ElegantOTA (by Ayush Sharma, v3.x)
WiFi, HTTPClient, WiFiClientSecure, WebServer, Preferences and time are provided by the ESP32 core — nothing to install for those.
Important — LedControl fix for ESP32: the LedControl library includes
<avr/pgmspace.h>, which does not exist on the ESP32 and causes a compile error. OpenArduino/libraries/LedControl/src/LedControl.hand replace#include <avr/pgmspace.h>with
#if defined(ESP32) || defined(ESP8266) #include <pgmspace.h> #else #include <avr/pgmspace.h> #endif(A future library update may overwrite this edit; just re‑apply it if so.)
- Install the ESP32 boards package (Espressif) via the Boards Manager.
- Keep
ESP32_BTCPRICE.inoandwebserver.htogether in a folder namedESP32_BTCPRICE. - Apply the LedControl fix above.
- Select Tools → Board → ESP32 Dev Module.
- Set Flash Size: 4MB, Partition Scheme: Default 4MB with spiffs (leaves room for OTA).
- Select the correct Port, then upload.
If you get an "async webserver" error from ElegantOTA, force the synchronous mode with
-D ELEGANTOTA_USE_ASYNC_WEBSERVER=0(it is the default for the standardWebServer).
On first boot the device has no saved WiFi, so it opens its own setup access point:
- Connect a phone or PC to the
BTCTICKERAPWiFi network (open network). - A captive portal usually opens automatically; otherwise browse to
http://192.168.4.1. - Pick your home network and enter its password.
- The device reboots and connects. Its local IP is printed on the serial monitor at 115200 baud.
Credentials are stored and reused on subsequent boots. You can clear them anytime from the web UI (Settings → Reset WiFi) to reopen the portal.
Open http://<device-ip>/ in a browser. The page is dark‑themed by default (toggleable) and organised in tabs:
- Bitcoin Price — current price and a chart of the on‑device price history.
- MQTT Configuration — broker IP, user and password (applied live, no reboot).
- Alarm Configuration — alarm time and enable toggle.
- Brightness — a 0–15 slider (applied when released).
- Settings — currency (USD/EUR), price/time toggle interval, timezone, MQTT topic, WiFi reset and firmware version.
- Firmware Update — opens the ElegantOTA page at
/updateto upload a new.bin.
The header always shows the time and whether the alarm is ON (with its time) or OFF.
The price history is kept in RAM and survives page reloads, but resets on a device reboot/power cycle.
The device polls Coinbase once per minute:
https://api.coinbase.com/v2/prices/BTC-USD/spot (or BTC-EUR)
This endpoint needs no account and no API key. TLS certificate validation is disabled (setInsecure()) to keep things simple — acceptable for a read‑only price display.
The ESP32 does not play audio itself. At the alarm time it publishes an MQTT message on the configured topic (default sonos/play_alarm_btcclock), and a Home Assistant automation plays a track on a Sonos speaker.
The simplest reliable method is to add the track you want as a Sonos favorite (in the Sonos app, with your music service connected) and play it by name. Example automation:
- id: '1727641210000'
alias: Play alarm on Sonos via MQTT
triggers:
- trigger: mqtt
topic: sonos/play_alarm_btcclock
actions:
- action: media_player.volume_set
target:
entity_id: media_player.sonosmove
data:
volume_level: 0.3
- action: media_player.play_media
target:
entity_id: media_player.sonosmove
data:
media_content_type: favorite_item_id
media_content_id: "Your Sonos favorite name"
mode: singleIf you change the MQTT topic in the device Settings, update the automation's trigger topic to match.
MQTT details: the broker is the one used by Home Assistant (e.g. the Mosquitto add‑on) on port 1883 — not the Home Assistant web port (8123). Enter the broker's IP and a valid MQTT user/password in the MQTT tab.
Open the Firmware Update tab and click Open firmware updater (or browse to http://<device-ip>/update). Compile a new .bin in the Arduino IDE (Sketch → Export Compiled Binary) and upload it. Remember to bump FIRMWARE_VERSION in the sketch for each release so the UI reflects the running version.
- Price history lives in RAM (24 h at 15‑minute resolution) and resets on reboot. It can be moved to LittleFS for reboot persistence if needed.
- TLS runs in insecure mode (no certificate pinning).
- The on‑board power LED cannot be turned off in software; remove it (or its series resistor) physically if you want it dark.
Original project and 3D‑printed enclosure by Unco16. Ported to ESP32 with additional features.