QRCode (community library)

Summary

A simple QR code generation library. A simple QR code generation library.

Example Build Testing

Library Read Me

This content is provided by the library maintainer and has not been validated or approved.

QRCode

A simple library for generating QR codes in C, ported to Partice Core/Photon/Electron by Tim Siggins.

Features:

• Stack-based (no heap necessary; but you can use heap if you want)
• Low-memory foot print (relatively)
• Compile-time stripping of unecessary logic
• MIT License; do with this as you please

Installing

Search for qrcode in the particle IDE to include this in your project.

API

Generate a QR Code

// The structure to manage the QR code
QRCode qrcode;

// Allocate a chunk of memory to store the QR code
uint8_t qrcodeBytes[qrcode_getBufferSize()];

qrcode_initText(&qrcode, qrcodeBytes, 3, ECC_LOW, "HELLO WORLD");

Draw a QR Code

How a QR code is used will vary greatly from project to project. For example:

• Display on an OLED screen (128x64 nicely supports 2 side-by-side version 3 QR codes)
• Print as a bitmap on a thermal printer
• Store as a BMP (or with a some extra work, possibly a PNG) on an SD card

The following example prints a QR code to the Serial Monitor (it likely will not be scannable, but is just for demonstration purposes).

for (uint8 y = 0; y < qrcode.size; y++) {
for (uint8 x = 0; x < qrcode.size; x++) {
if (qrcode_getModule(&qrcode, x, y) {
Serial.print("**");
} else {
Serial.print("  ");
}
}
Serial.print("\n");
}

What is Version, Error Correction and Mode?

A QR code is composed of many little squares, called modules, which represent encoded data, with additional error correction (allowing partially damaged QR codes to still be read).

The version of a QR code is a number between 1 and 40 (inclusive), which indicates the size of the QR code. The width and height of a QR code are always equal (it is square) and are equal to 4 * version + 17.

The level of error correction is a number between 0 and 3 (inclusive), or can be one of the symbolic names ECC_LOW, ECC_MEDIUM, ECC_QUARTILE and ECC_HIGH. Higher levels of error correction sacrifice data capacity, but allow a larger portion of the QR code to be damaged or unreadable.

The mode of a QR code is determined by the data being encoded. Each mode is encoded internally using a compact representation, so lower modes can contain more data.

• NUMERIC: numbers (0-9)
• ALPHANUMERIC: uppercase letters (A-Z), numbers (0-9), the space (), dollar sign ($), percent sign (%), asterisk (*), plus (+), minus (-), decimal point (.), slash (/) and colon (:).
• BYTE: any character

Data Capacities

Special Thanks

A HUGE thank you to nayuki for the QR code C++ library which was critical in development of this library.

License

MIT License.

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