Signal K ESP Library (EspSigK)

This library implements Signal K v1 protocol for sensors. It can be used as part of sensor code authenticating and sending the measurement data (so called "deltas").

Currently the library provides the following:

• Wifi connection/reconnection
• mDNS/SSDP Discovery
• Hosts a small webpage to display deltas and reset the authentication token
• Websocket Server
• Websocket Client, with auto discovery of Signal K server
• Sending authentication request to Signal K server and using the given authentication token
• Sending deltas with one or more values

However, the library does not do the following:

• Receive deltas and pass message to callback function

Supported microcontrollers:

• ESP8266 (tested Wemos D1, ESP-01S 1M), EspSigK_ESP8266
• ESP32 (tested ESP-WROOM32), EspSigK_ESP32

Check out SensESP

Before starting to use EspSigK check out SensESP which is the market leader of Signal K sensor libraries.

Developing

Compiler Directives

• Microcontroller: EspSigK_ESP8266 or EspSigK_ESP32
• Sensor HTTP server port for rebooting and resetting the server (defined in EspSigK.h): ESPSIGK_HTTP_SERVER_PORT
• Sensor Websocket server port for debugging SignalK deltas (defined in EspSigK.h): ESPSIGK_DEBUG_WEBSOCKET_SERVER_PORT

Example

Define either EspSigK_ESP8266 or EspSigK_ESP32 at compile time. When using PlatformIO you can define symbols in platformio.ini:

build_flags = -DEspSigK_ESP8266

Don't forget to include EspSigK library in platformio.ini:

lib_deps =
    https://github.com/mplattu/EspSigK

Sample app:

#include <Arduino.h>
#include "EspSigK.h"

const String hostname  = "Tester";       // Hostname for network discovery and sensor name for SignalK
const String ssid      = "mywifi";       // SSID to connect to
const String ssidPass  = "superSecret";  // Password for wifi

WiFiClient wiFiClient;
EspSigK sigK(hostname, ssid, ssidPass, &wiFiClient);

void setup() {
  Serial.begin(115200);

  // Setting the server address is optional. If not set we try to discover server with mDNS.
  sigK.setServerHost("192.168.0.50");   
  
  // Start everything. Connect to wifi, setup services, etc...
  sigK.begin();                         
}

// This function will be executed during safeDelay() function, see below
void localHandler() {
  Serial.println("Executing localHandler()");
}

void loop() {
  // There are two options to send deltas:

  // Send multiple values in one message...
  sigK.addDeltaValue("some.signalk.path", 3.413);
  sigK.addDeltaValue("some.other.path", true);
  sigK.addDeltaValue("navigation.position", "{\"latitude\":60.19145,\"longitude\":25.05422}", true);
  sigK.sendDelta();
  
  // ...or send a single value
  sigK.sendDelta("some.signalk.path", 3.413);

  // Use this delay function instead of built-in delay()
  // This function will continue handling connections etc. instead of blocking
  sigK.safeDelay(1000);
  // Optionally, you can pass a callback function pointer. This function will
  // be executed during wait time.
  // sigK.safeDelay(1000, &localHandler);

  // If you don't use the delay function above call this one every
  // loop in order to handle http/websocket connections etc.
  sigK.handle();
  // The top-level callback function can be passed to handle(), too.
  // sigK.handle(&localHandler);
}

For more examples see examples/.

Debugging

To show the Signal K delta updates:

1. Make sure you have defined ESPSIGK_HTTP_SERVER_PORT and ESPSIGK_DEBUG_WEBSOCKET_SERVER_PORT.
2. Start your sensor and find the IP of the device. If you have enabled serial debug messages (setPrintDebugSerial(true)) you'll get the IP from the serial monitor.
3. Connect your browser to http://YOURIP:ESPSIGK_HTTP_SERVER_PORT. If everything goes as planned, the delta objects are shown on the page and dumped to the browser console.

If you do not get the messages but see a message Disconnected! #1006 try a different browser. This means the browser hasn't been able to open a websocket connection to the sensor.

Publishing

1. Invent a new version number. EspSigK uses semantic versioning
2. Update Changelog (below) and set version number to library.json and library.properties
3. Push changes
4. Create a new release
5. Enter the new version number to "Choose a tag" field (e.g. "v1.6.0" - note the "v")
6. Fill "Release title" field with the release name (see your Changelog)
7. Copy release note markup from README.md to "Describe this release" textarea
8. Click "Publish release"

Changelog

0.5.1 "Specify bblanchon/ArduinoJson v6" 26-OCT-2025

• Keep using v6 as suggested at https://arduinojson.org/v7/how-to/upgrade-from-v6/: "If your program targets 8-bit microcontrollers, I recommend keeping version 6."

0.5.0 "Send JSON-formatted deltas" 26-OCT-2025

• Send JSON-formatted deltas

0.4.0 "Create random device UUIDs" 17-OCT-2023

• Major fix: Added missing random seed to device UUID generation
• Added default EspSigK debug HTTP server at port 8080
• Added option to call local handler during safeDelay()
• Added overloaded deltaValue() functions to String and const char * value types
• Added setWiFiConnectTimeout() and changed default wifi timeout from 3 seconds to 10 secs
• Fix: Added missing ESP32SSDP library (required for ESP32)
• Fix: Added prefix for internal defined names (settings) to overcome overlapping names
• Fix: Do not block handle() calls if wifi is not available

0.3.0 "Support for ESP32" 24-MAR-2023

• Added support for ESP32
• Fixed unresponsive HTTP server during SignalK authentication process
• Added reboot call to HTTP api & UI

0.2.0 "Authentication" 21-MAR-2023

• SignalK v1 authentication process
• added library.json for better PlatformIO support
• directory structure according to PlatformIO documentation
• a new maintainer for the project

0.1.0 "Initial version" 27-JUN-2018

• Connecting wifi and sending deltas with pre-set authentication token
• Supported MCU: ESP8266