Data Send/Recv

This document describes how to exchange data between a Lua plugin running on the obniz OS and the obniz JavaScript SDK.

Overview

You can facilitate communication between a Lua plugin operating on the device OS and the JavaScript SDK. This allows for bidirectional data transfer and efficient handling of large data sets.

obniz.plugin.send()

Sends a binary data sequence from the obniz.js side to the Lua plugin.

Javascript Example

// Send string data
obniz.plugin.send("obniz.js send data get device?");

// Send byte array
obniz.plugin.send([0x00, 0x01, 0x02]);

Lua Plugin Side

On the Lua side, use the on_command() function to receive the data.

function on_command(command)
  -- 'command' contains the data sent from JS
  os.log(command)
end

obniz.plugin.onreceive

This event handler receives a binary data sequence sent from the Lua plugin to the obniz.js side.

Javascript Example

obniz.plugin.onreceive = (data) => {
  console.log(data);
};

Lua Plugin Side

Use cloud.pluginSend() to send data to the JavaScript SDK.

cloud.pluginSend("123");

obniz.plugin.onFrameStart / onFrameEnd

These handlers are triggered when frame information is sent from the plugin side.

These functions are particularly useful for segmenting and managing large data transfers.

• onFrameStart: Receives the frame_id and the total length of the data.
• onreceive: For large payloads, the data will be received in multiple chunks through this handler.
• onFrameEnd: Called once all data defined in the frame has been completely received.

Javascript Example

// Handle the start of a frame
obniz.plugin.onFrameStart = (frame_id, length) => {
  console.log(`Frame start: ID=${frame_id}, Total Length=${length}`);
};

// Handle the end of a frame
obniz.plugin.onFrameEnd = () => {
  console.log("Frame reception completed");
};

// Receive chunks of data
obniz.plugin.onreceive = (data) => {
  console.log(`Received chunk: ${Buffer.from(data).toString()}`);
};

Lua Plugin Side

To use framing in a Lua plugin, use the following commands:

local frame_id = 1
local total_length = 9

cloud.pluginSendFrameStart(frame_id, total_length); -- Start framing 

cloud.pluginSend("123");
cloud.pluginSend("456");
cloud.pluginSend("789");

cloud.pluginSendFrameEnd(); -- End framing