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AlphaLoc

AlphaLoc is an ESP32 application that allows embedding GPS location data directly into Sony Alpha camera photos via Bluetooth Low Energy (BLE). It acts as a bridge between a standard GPS module and your Sony camera, providing real-time geolocation tagging.

Features

  • Automatic Geotagging: Sends GPS coordinates (Latitude, Longitude, Altitude, Time) to the camera.
  • BLE Connection: Emulates a smartphone location provider for Sony cameras.
  • Dual Configuration: Configurable via a Web Interface (WiFi) or BLE characteristics.
  • Status Indicators: NeoPixel (RGB LED) feedback for Camera connection, GPS fix, Battery, and WiFi status.
  • Low Power: Supports disabling external peripherals (like Stemma QT) to save power.

Hardware Support

The project is set up for PlatformIO and currently supports:

Board Environment Pinout
DFRobot Beetle ESP32-C6 esp32c6 GPS TX: 5, GPS RX: 4, NeoPixel: 6
Adafruit Feather ESP32-S3 esp32s3 GPS TX: 38, GPS RX: 39, NeoPixel: 6

You can easily adapt it to other ESP32 boards by modifying platformio.ini.

Parts List

The following is a parts list of what I ended up with.

Models

  • Holder: Holder for the batteries, ESP32, optional wifi antenna, ...
  • Cover: Cover with a press fit for the holder and room for the LED board.
  • Cover Large: Same as cover but taller and with room for a larger, external GPS antenna.

Usage

1. Initial Setup

  1. Connect your GPS module (e.g., GY-GPS6MV2 or an Adafruit Ultimate GPS Featherwing) to the defined TX/RX pins.

  2. Flash the firmware using PlatformIO.

    pio run -e esp32c6 -t upload

  3. Power on the device.

2. Pairing with Camera

  1. On your Sony Alpha camera, go to Network -> Bluetooth Settings.
  2. Enable Bluetooth Function.
  3. Select Pairing.
  4. The camera should discover "AlphaLoc". Select it to pair.
  5. Once paired, go to Location Info. Link Set. and enable it.
  6. The camera should now show the GPS icon (solid when receiving data).

3. LED Status Codes

The NeoPixel LED provides a visual "heartbeat" every 5 seconds. It flashes multiple colors in sequence to report the status of different subsystems:

Sequence: [Camera Status] -> [GPS Status] -> [Battery Status] -> [WiFi Status] -> [Sleep]

  1. First Flash: Camera Connection
    • 🟢 Green: Connected to camera and bonded.
    • 🔵 Blue: Connected to camera but not bonded yet.
    • 🔴 Red: Not connected.
  2. Second Flash: GPS Fix
    • 🟢 Green: Valid 3D GPS Fix acquired.
    • 🟣 Violet: Fake GPS fix (injected when ALPHALOC_FAKE_GPS=1).
    • 🔴 Red: No fix (searching for satellites).
  3. Third Flash: Battery Level (Optional)
    • 🟢 Green: > 50%
    • 🟡 Yellow: > 30%
    • 🔴 Red: <= 30%
  4. Fourth Flash: WiFi/Config (Optional)
    • Only appears during the startup "Config Window" (first 5 minutes).
    • 🔵 Blue: Web server is active.
    • ⚫ (Off): Config window closed, WiFi disabled to save power.

Example:

  • 🔴-🔴-🟢-🔵: No camera, no GPS, battery good, config mode active (just turned on).
  • 🔵-🟢-🟡-⚫: Camera connected (not bonded yet), GPS fixed, battery medium, normal operation (config closed).
  • 🟢-🟢-🔴-⚫: Camera connected (bonded), GPS fixed, battery low, normal operation (config closed).
  • 🔵-🟣-🟢-⚫: Camera connected (not bonded yet), fake GPS fixed, battery good, normal operation (config closed).

4. Configuration

⚠️ SECURITY WARNING: The BLE configuration service is DISABLED by default for security reasons. When enabled, it allows UNAUTHENTICATED access to device settings including WiFi passwords. Only enable it (ALPHALOC_BLE_CONFIG=1) in trusted environments or for initial setup, then rebuild with it disabled.

On startup, AlphaLoc enters a Configuration Window (default 5 minutes). During this time, you can change settings via WiFi (if ALPHALOC_WIFI_WEB=1) or BLE (if ALPHALOC_BLE_CONFIG=1).

web

Configuration Parameters

Parameter Description Default
Camera Name Prefix Filter which cameras to connect to. Useful if you have multiple Sonys. SonyA7
Camera MAC Prefix Connect only to a specific MAC address prefix. Empty matches any. (Empty)
TZ Offset Timezone offset in minutes (e.g., 60 for UTC+1). 60
DST Offset Daylight Savings Time offset in minutes. 60
WiFi SSID/Pass Credentials for connecting to your home WiFi. WiFi / changeme
AP SSID/Pass Credentials for the hotspot created by AlphaLoc. AlphaLoc / alphaloc1234
Max GPS Age How long (seconds) to reuse old coordinates if GPS signal is lost. 300

Method A: WiFi Web Interface

AlphaLoc tries to connect to the configured WiFi as a client:

  • Default SSID: WiFi
  • Default Password: changeme
  • IP: assigned via DHCP

If it can't connect to the WiFi, it starts an access point itself:

  • SSID: AlphaLoc
  • Password: alphaloc1234
  • IP: 192.168.4.1 (direct link to webserver: http://192.168.4.1/)

To enable this, set the build flag (ALPHALOC_WIFI_WEB=1 in platformio.ini).

Method B: BLE Configuration

You can use a generic BLE app (like nRF Connect) to write to the configuration service.

Service UUID: B1F0B4D5-797B-5A9E-5B4F-4A1F01007EA1

Characteristic Name UUID (Base B1F0...) R/W Type (Over BLE) Description
Camera Name Prefix ...02007EA1 R/W String Camera name identifier
Camera MAC Prefix ...03007EA1 R/W String MAC address filter
Timezone Offset ...04007EA1 R/W String (Int) Minutes from UTC
DST Offset ...05007EA1 R/W String (Int) Daylight Savings offset (minutes)
Wifi SSID ...07007EA1 R/W String Station SSID
Wifi Password ...08007EA1 R/W String Station Password
AP SSID ...09007EA1 R/W String Access Point SSID
AP Password ...0A007EA1 R/W String Access Point Password
Max GPS Age ...0B007EA1 R/W String (Int) Max age of GPS lock in seconds
GPS Lock ...0C007EA1 R String (0/1) 1 when GPS lock is valid
GPS Satellites ...0D007EA1 R String (Int) Satellites in view (from GGA)
GPS Constellations ...0E007EA1 R String (Int) Bitmask: 1=GPS, 2=GLONASS
Camera Connected ...0F007EA1 R String (0/1) BLE camera link active
Camera Bonded ...10007EA1 R String (0/1) Link bonded (after pairing)

Build-Time Secrets (Recommended)

If you want to keep WiFi credentials and camera filters out of git, place them in platformio.secrets.ini and keep the file ignored. The build merges these flags into every environment via platformio.ini.

Example platformio.secrets.ini with all supported defaults:

[secrets]
build_flags =
  -DALPHALOC_DEFAULT_WIFI_SSID="\"MyWifi\""
  -DALPHALOC_DEFAULT_WIFI_PASS="\"MyPass\""
  -DALPHALOC_DEFAULT_AP_SSID="\"AlphaLoc\""
  -DALPHALOC_DEFAULT_AP_PASS="\"AlphaLocPass\""
  -DALPHALOC_DEFAULT_CAMERA_NAME_PREFIX="\"SonyA7\""
  -DALPHALOC_DEFAULT_CAMERA_MAC_PREFIX="\"AA:BB:CC\""

These values are used as defaults on first boot (or after a factory reset) and can still be changed later via the WiFi or BLE config UIs.

BLE Client Details (Camera Link)

AlphaLoc acts as a BLE client to Sony cameras

Advertisement Filters

  • Manufacturer data: company ID 0x012D, product ID 0x0003
  • Optional name prefix filter: camera_name_prefix (if set)
  • Optional MAC prefix filter: camera_mac_prefix (if set)

Services and Identifiers

AlphaLoc looks for two Sony services (UUIDs are built from 16-bit IDs using the Sony base UUID):

Sony base UUID (constructed):
  00000000-0000-8000-ffff-ffff-ffff-ffff
  with 16-bit words inserted at positions:
    first = 0xDD00 / 0xFF00
    second = 0xDD00 / 0xFF00

It accepts either 128-bit UUIDs or 16-bit UUIDs:

  • Location Service: 0xDD00
  • Remote Service: 0xFF00

Characteristic Discovery

Within those services, AlphaLoc searches for:

Location Service (DD00)

  • 0xDD21: Flags read to determine if TZ/DST are required
  • 0xDD30: Lock location (0x00 - Off, 0x01 - On)
  • 0xDD31: Enable location updates (0x00 - Off, 0x01 - On)
  • 0xDD11: Location write characteristic; used for sending GPS payloads

Data is a 95 byte buffer

Offset Description Remark
[0:1] Payload Length (exclude these two bytes) 0x5D = 93 bytes
[2:4] Fixed Data 0x0802FC
[5] Flag of transmitting timezone offset and DST offset required 0x03 for transmit and 0x00 for do not transmit
[6:10] Fixed Data 0x0000101010
[11:14] Latitude (multiplied by 10000000) 0x0BF79E5E = 200777310 / 10000000 = 20.077731
[15:18] Longitude (multiplied by 10000000) 0x41C385A7 = 1103332775 / 10000000 = 110.3332775
[19:20] UTC Year 0x07E4 = 2020
[21] UTC Month 0x0B = 11
[22] UTC Day 0x05 = 5
[23] UTC Hour 0x04 = 4
[24] UTC Minute 0x02 = 2
[25] UTC Second 0x2A = 42
[26:90] Zeros 0x00
*[91:92] Difference between UTC and current timezone in minutes 0x01E0 = 480min = 8h (UTC+8)
*[93:94] Difference for DST in current timezone in minutes

Remote Service (FF00)

  • 0xFF02 (notification characteristic; CCCD 0x2902)

Connection/Discovery Flow (simplified)

ADV (Sony) --> connect
  |
  +--> discover DD00 (Location Service)
  |      +--> find DD11, DD21, DD30, DD31
  |      +--> read DD21 flag byte
  |      +--> enable location writes on DD11
  |
  +--> discover FF00 (Remote Service)
         +--> find FF02
         +--> find/guess CCCD (0x2902)
         +--> enable notifications

Sending Location

Once services and characteristics are resolved:

  • Builds a Sony-compatible location payload
  • Writes to DD11
  • Enables FF02 notifications after first location write (if required)

Configuration Options

  • Camera Name Prefix: Limits connection to cameras starting with this name (Default: "SonyA7").
  • Timezone/DST: Offset in minutes for timestamp correction.
  • Max GPS Age: How long to keep sending the last known location if GPS signal is lost.

Building

This project uses the Espressif IoT Development Framework (ESP-IDF) within PlatformIO. Check platformio.ini for build flags and pin definitions.

; Example Override
build_flags =
  -DGPS_UART_TX_PIN=5
  -DGPS_UART_RX_PIN=4

Build Environments

The platformio.ini file defines several build environments for different purposes:

  • env:esp32c6: The standard production build for the ESP32-C6. Logging is disabled for performance.
  • env:esp32c6-debug: A debugging environment.
    • Enables verbose logging (ALPHALOC_VERBOSE=1).
    • Enables Fake GPS (ALPHALOC_FAKE_GPS=1): Simulates a stationary location (Munich) for testing without a GPS module or satellite lock.
  • env:esp32c6-debug-gps: Debugging environment using real GPS data but with verbose logging enabled.
  • env:esp32s3: The standard production build for the ESP32-S3. Logging is disabled for performance.
  • env:esp32s3-debug: A debugging environment.
    • Enables verbose logging (ALPHALOC_VERBOSE=1).
    • Enables Fake GPS (ALPHALOC_FAKE_GPS=1): Simulates a stationary location (Munich) for testing without a GPS module or satellite lock.
  • env:esp32s3-debug-gps: Debugging environment using real GPS data but with verbose logging enabled.

Build Flags

You can customize the firmware behavior using these compilation flags in platformio.ini:

Flag Description Default
ALPHALOC_WIFI_WEB Enable internal settings web server. Set to 0 to remove WiFi stack and save power/flash. 1
ALPHALOC_BLE_CONFIG Enable BLE configuration service. Note: This allows reading and writing the config via BLE unauthenticated! 0 (DISABLED)
ALPHALOC_VERBOSE Enable extensive debug logging to serial UART. 0
ALPHALOC_FAKE_GPS Ignore UART GPS and output a static test location. 0
ALPHALOC_NEOPIXEL_PIN GPIO pin number for the WS2812B NeoPixel. (Board dependent)
ALPHALOC_BATTERY_MONITOR Enable MAX17048 / LC709203F battery monitor over I2C. 0
ALPHALOC_BATTERY_SDA_PIN I2C SDA pin for battery monitor. (Board dependent)
ALPHALOC_BATTERY_SCL_PIN I2C SCL pin for battery monitor. (Board dependent)
ALPHALOC_BATTERY_I2C_POWER_PIN Optional power-enable pin for I2C battery monitor. (Unset)
GPS_UART_TX_PIN TX Pin for GPS Serial (Connects to GPS RX). (Board dependent)
GPS_UART_RX_PIN RX Pin for GPS Serial (Connects to GPS TX). (Board dependent)
DALPHALOC_FACTORY_RESET If set to 1, wipes NVS settings on boot. Dangerous. Undefined

Security Best Practices:

  • Keep ALPHALOC_BLE_CONFIG=0 in production builds
  • Only enable BLE config for initial setup in controlled environments
  • Use WiFi config (ALPHALOC_WIFI_WEB=1) with strong AP password instead
  • Change default WiFi credentials immediately after first boot

References

There is a bunch of work done by others before me which greatly helped figuring out how the BLE protocol works with the Sony Alpha cameras. I'm sure I'm forgetting a bunch but to at least name a few:

About

ESP32 application to receive a GPS/GNSS location and send it to a Sony Alpha camera.

Topics

esp32 gps sony-alpha-cameras

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Apache-2.0 license
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