This project works together with the Adafruit Bluefruit LE Connect app for iOS and Android to control a scrolling message across the 18x5 RGB LED matrix.

When first run, the glasses will scroll the message “RUN BLUEFRUIT CONNECT APP”. Self explanatory. When you run this app on your phone or tablet, you’ll see the EyeLights device as “LED Glasses Driver nRF52840.” Tap the corresponding “Connect” button.

Once connected, the app will show this “MODULES” screen. The items of interest here are UART and CONTROLLER.

UART provides a text field into which you can type a message, up to a maximum of 50 characters. Press the “Send” button to update the glasses.

Tip: the exclamation point character (“!”) is off-limits…that has special meaning to the software. Any other ASCII characters (letters, numbers, punctuation) are fair game. Upper or lower case doesn’t matter…because the matrix is small and requires a chunky font, everything will be converted to upper case.

Or, from the “Controller” screen, click “Color Picker.”

Here you can select a color from the wheel and a brightness level with the slider. Tapping “Send selected color” will change the color of the scrolling message.

The above two settings — message and color — are the only options that have any bearing on this project. Although the app can issue other data like game pad buttons or a compass heading, we didn’t want to go overboard and make the code too complex to follow. Consider it a starting point for your own ideas.

The text looks rough when testing right in front of you…but from a few feet away the image blends together and is more legible. Try it with a mirror!

If you’d prefer a pre-compiled binary: download this .UF2 file. Connect the EyeLights driver board to your computer with a USB cable, set the power switch “on,” double-tap the reset button and a small flash drive named GLASSESBOOT appears. Then drag the .UF2 file to GLASSESBOOT and wait several seconds while it copies.

// SPDX-FileCopyrightText: 2021 Phil Burgess for Adafruit Industries
// SPDX-License-Identifier: MIT

BLUETOOTH SCROLLING MESSAGE for Adafruit EyeLights (LED Glasses + Driver).
Use BLUEFRUIT CONNECT app on iOS or Android to connect to LED glasses.
Use the app's UART input to enter a new message.
Use the app's Color Picker (under "Controller") to change text color.
This is based on the glassesdemo-3-smooth example from the
Adafruit_IS31FL3741 library, with Bluetooth additions on top. If this
code all seems a bit too much, you can start with that example (or the two
that precede it) to gain an understanding of the LED glasses basics, then
return here to see what the extra Bluetooth layers do.

#include <Adafruit_IS31FL3741.h> // For LED driver
#include <bluefruit.h>           // For Bluetooth communication
#include <EyeLightsCanvasFont.h> // Smooth scrolly font for glasses

// These items are over in the packetParser.cpp tab:
extern uint8_t packetbuffer[];
extern uint8_t readPacket(BLEUart *ble, uint16_t timeout);
extern int8_t packetType(uint8_t *buf, uint8_t len);
extern float parsefloat(uint8_t *buffer);
extern void printHex(const uint8_t * data, const uint32_t numBytes);


// 'Buffered' glasses for buttery animation,
// 'true' to allocate a drawing canvas for smooth graphics:
Adafruit_EyeLights_buffered glasses(true);
GFXcanvas16 *canvas; // Pointer to glasses' canvas object
// Because 'canvas' is a pointer, always use -> when calling
// drawing functions there. 'glasses' is an object in itself,
// so . is used when calling its functions.

char message[51] = "Run Bluefruit Connect app"; // Scrolling message
int16_t text_x;   // Message position on canvas
int16_t text_min; // Leftmost position before restarting scroll

BLEUart bleuart;  // Bluetooth low energy UART

int8_t last_packet_type = 99; // Last BLE packet type, init to nonsense value

// ONE-TIME SETUP ---------

void setup() { // Runs once at program start...


  // Configure and start the BLE UART service
  startAdv(); // Set up and start advertising

  if (!glasses.begin()) err("IS3741 not found", 2);

  canvas = glasses.getCanvas();
  if (!canvas) err("Can't allocate canvas", 5);

  // Configure glasses for full brightness and enable output

  // Set up for scrolling text, initialize color and position
  canvas->setTextWrap(false); // Allow text to extend off edges
  canvas->setTextColor(glasses.color565(0x303030)); // Dim white to start
  reposition_text(); // Sets up initial position & scroll limit

// Crude error handler, prints message to Serial console, flashes LED
void err(char *str, uint8_t hz) {
  for (;;) digitalWrite(LED_BUILTIN, (millis() * hz / 500) & 1);

// Set up, start BLE advertising
void startAdv(void) {
  // Advertising packet
  // Include the BLE UART (AKA 'NUS') 128-bit UUID

  // Secondary Scan Response packet (optional)
  // Since there is no room for 'Name' in Advertising packet

  // Start Advertising
  // - Enable auto advertising if disconnected
  // - Interval:  fast mode = 20 ms, slow mode = 152.5 ms
  // - Timeout for fast mode is 30 seconds
  // - Start(timeout) with timeout = 0 will advertise forever (until connected)
  // For recommended advertising interval
  Bluefruit.Advertising.setInterval(32, 244); // in unit of 0.625 ms
  Bluefruit.Advertising.setFastTimeout(30);   // number of seconds in fast mode
  Bluefruit.Advertising.start(0);             // 0 = Don't stop advertising after n seconds  

// MAIN LOOP --------------

void loop() { // Repeat forever...
  // The packet read timeout (9 ms here) also determines the text
  // scrolling speed -- if no data is received over BLE in that time,
  // the function exits and returns here with len=0.
  uint8_t len = readPacket(&bleuart, 9);
  if (len) {
    int8_t type =  packetType(packetbuffer, len);
    // The Bluefruit Connect app can return a variety of data from
    // a phone's sensors. To keep this example relatively simple,
    // we'll only look at color and text, but here's where others
    // would go if we were to extend this. See Bluefruit library
    // examples for the packet data formats. packetParser.cpp
    // has a couple functions not used in this code but that may be
    // helpful in interpreting these other packet types.
    switch(type) {
     case 0: // Accelerometer
     case 1: // Gyro:
     case 2: // Magnetometer
     case 3: // Quaternion
     case 4: // Button
     case 5: // Color
      // packetbuffer[2] through [4] contain R, G, B byte values.
      // Because the drawing canvas uses lower-precision '565' color,
      // and because glasses.scale() applies gamma correction and may
      // quantize the dimmest colors to 0, set a brightness floor here
      // so text isn't invisible.
      for (uint8_t i=2; i<=4; i++) {
        if (packetbuffer[i] < 0x20) packetbuffer[i] = 0x20;
        packetbuffer[2], packetbuffer[3], packetbuffer[4])));
     case 6: // Location
     default: // -1
      // Packet is not one of the Bluefruit Connect types. Most programs
      // will ignore/reject it as not valud, but in this case we accept
      // it as a freeform string for the scrolling message.
      if (last_packet_type != -1) {
        // If prior data was a packet, this is a new freeform string,
        // initialize the message string with it...
        strncpy(message, (char *)packetbuffer, 20);
      } else {
        // If prior data was also a freeform string, concatenate this onto
        // the message (up to the max message length). BLE packets can only
        // be so large, so long strings are broken into multiple packets.
        uint8_t message_len = strlen(message);
        uint8_t max_append = sizeof message - 1 - message_len;
        strncpy(&message[message_len], (char *)packetbuffer, max_append);
        len = message_len + max_append;
      message[len] = 0; // End of string NUL char
      reposition_text(); // Reset text off right edge of canvas
    last_packet_type = type; // Save packet type for next pass
  } else {
    last_packet_type = 99; // BLE read timeout, reset last type to nonsense

  canvas->fillScreen(0); // Clear the whole drawing canvas
  // Update text to new position, and draw on canvas
  if (--text_x < text_min) {  // If text scrolls off left edge,
    text_x = canvas->width(); // reset position off right edge
  canvas->setCursor(text_x, canvas->height());
  glasses.scale(); // 1:3 downsample canvas to LED matrix;  // MUST call show() to update matrix

// When new message text is assigned, call this to reset its position
// off the right edge and calculate column where scrolling resets.
void reposition_text() {
  uint16_t w, h, ignore;
  canvas->getTextBounds(message, 0, 0, (int16_t *)&ignore, (int16_t *)&ignore, &w, &ignore);
  text_x = canvas->width();
  text_min = -w; // Off left edge this many pixels

This guide was first published on Oct 12, 2021. It was last updated on 2023-12-04 20:45:50 -0500.

This page (Bluetooth Message Scroller) was last updated on Oct 07, 2021.

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