PIXELS - A super simple LED application layer

Don't use right now, this is unfinished and a much better version will be released soon

This protocols goal is to allow for sending pixel data (color values) to rgb and rgbw stripes in a performant way. This is especially useful for sending data in "realtime" to led stripes connected to an ESP32 via WIFI/UDP.

This protocol was written originally for udpx.

Installation

PlatformIO

PlatformIO should automatically install this package if https://github.com/IoTPanic/pixels.git is added to the lib_deps section of platformio.ini. We plan on adding this library to PlatformIO library manager soon. If the current method is used, the library will be git cloned into .pio/libdeps/ so if you need to switch to a development branch you can, remember to hit the trash can icon and clean the cache before building agian.

Arduino

Coming Soon, Just need to make a library.properties but will be installable like any library.

Usage

1. Install with the instructions provided in the installation section.
2. If using RGBW LEDs, set the RGBW constant in pixels.h to 1.
3. If using LEDs that communicate in the GRB order, set the GRB constant in pixels.h to 1.
4. Set the DRIVERMETHOD in pixels.h to inform the neopixel library how to implement itself if your platform is not an ESP32 or ESP8266. Remember to remove the #error line to allow the library to compile if true.
5. Import the PIXELS constructor into your application.
6. In the setup code, use bool addChannel(int pin, unsigned LED_count, uint8_t channel_number) to connect one or many LED strips.
7. Call bool PIXELS::receive(uint8_t *pyld, unsigned length) when ever pixels data is received with pyld being a uint8_t array and length being the array length. You may use any transport method you want, but check out s - Little Stream - Embedded streaming layer for UDPX.

Message Structure

A message consists of a header, a payload and a crc-check:

Header (5Bytes)	Payload (x Bytes)	CRC-Check (1 Byte)

Header

Byte Number:	1	2	3	4-5
	Message Type	Sync Word	Channel Number	Length of payload
Data Type	Uint8	Uint8	Uint8	16 bit LSB unsigned integer
Example	HEX: 0x50 / ASCII: 80		1	144

Message Type

The starting byte must be 0x50 which is ascii uppercase 'P'. (This stands for 'pixels'). This is to verify that the message is in fact pixel data.

There could be other protocols that always start with 0x50, but chances are good that you'll not face that kind of problem.

Sync Word

This is to verify the right client is connected and the right mode is on.

Channel Number

Which channel of the controller should consume the payload to be sent?

Length of payload

How many pixels will be in the payload?

Payload

Byte Number:	1	2	3	4	...
	R	G	B	(W)	...
Data Type	Uint8	Uint8	Uint8	Uint8	...
Example	16	155	43	0	...

The payload consists of RGB or RGBW values, depending on which mode is used. The number of values sent in the payload must match "Length of payload" setting in the message header. An RGB Value consists of 3 Uint8 values representing the brightness for the colors Red, Green and Blue.

Example: this is 'red' (#ff0000)

255	0	0

An RGBW Value consists of 4 Uint8 values representing the brightness for the colors Red, Green and Blue and White. Example: this is 'pure white' using the white led of an rgbw strip.

0	0	0	255

CRC Check

Byte Number:	1
	CRC
Data Type	Uint8
Example	34

example implementation:

uint8_t crc = 0x0;
for(uint i = 0; i<size;i++){
   crc = crc ^ payload[i];
}