Web accessible Arduino controller for RGB led strip

Intro

Here are instructions for making a LED strip that can be controlled via an Web API.

The strip can show any color combination with red, green and blue LEDs:

LEDs can be controlled individually. Here is a flame effect:

Software

API

The LED API can receive a number of commands. Number parameters are given as two-digit hex numbers. Colors are given as three two-digit hex numbers, for red, green and blue color component.

Commands are sent as query parameters of a HTTP GET request to the server. For example http://<hostname>/?s808000.

Command	Description	Format	Example	Explanation
c	clear all pixels	c	c	turns off all pixels
s	set all pixels to a single color	s[color]	sff00ff	set all pixels to bright magenta
p	draw a single pixel	p[position][color]	p28ffffff	set pixel number 40 (0x28 in hex) to white
a	set colors from an array	a[number of pixels][color1][color2]...	a03ff0000ffff0000ff00	set three colors: red, yellow and green
g	draw a color gradient	g[start position][end position][color1][color2]	g0010ff0000ffff00	draw a 16 pixel gradient from red to yellow at the start of the led strip
m	draw a moving sprite	m[background r][background g][background b][size of sprite][sprite position][sprite speed][color1][color2]...	m000000040084000500003000006000ffffff	animate a white pixel with green fading tail quite slowly slowly on a black background
f	animate flames	f[fuel amount][damping amount]	f2f10
b	animate aurora borealis	b[speed][centering][center color][edge color]	b240150ff5005ff05

Implementation

When the microcontroller starts, it initializes the WiFi shield and the LED strips, then connects a WiFi router and sets up a HTTP server listening on port 80.

Add name and password of your WiFi router in server/credentials.h.

The main loop does the following: When a HTTP client is available, it reads a line from the request, processes the command and send a response to the HTTP client. Finally the loop updates the LEDs.

Here is a simplified version of the main loop in `server/server.ino:

void loop() {
  WiFiClient client = server.available();
  if (client) {                      
    currentLine = readLine(client);
    client.flush();
    processLedCommand(currentLine);      
    client.println(httpResponse);
    client.stop();
  }
  updateLeds();
}

Electronics

• LEDs: 4 meter Adafruit DotStar Digital LED Strip that has 240 individually-addressable RGB LEDs
• microcontroller: Adafruit Feather M0 WiFi - ATSAMD21 + ATWINC1500 Arduino board with WiFi capability.
• power supply: 5V 10A switching power supply for the LEDs

Schematic

Here is a schematic of how the power supply (on the left), microcontroller and LED strip (on the right) are connected:

Pins used on the controller

Pin	Description	Wire color
GND	ground	black
VBUS	5V power	red
5	data to led strip	green
6	clock to led strip	yellow

Feather M0 pinouts without annotations

Enclosure

Here is everything put together in the enclosure:

Image of finished enclosure without annotations

There is a Micro USB connector for flashing the microcontroller. I added a power cord that goes to the other end of the LED strip to make sure that all leds receive power evenly.

The enclosure is 3D printed and has a sliding lid.

Here are the 3D models of the bottom and lid of the enclosure:

• led_strip_controller_enclosure_bottom.stl
• led_strip_controller_enclosure_lid.stl