To reiterate: install either the nRF UART app (available for both Android and iOS) or the Adafruit Bluetooth LE Connect app (iOS only) on a late-model phone or tablet that supports Bluetooth LE.
The status LED on the Arduino board will flash quickly while it awaits a Bluetooth connection. Running one of the above apps on your phone or tablet, select “Connect” or “UART Monitor.” Once a connection has been established, the LED on the Arduino will flash slowly.
Type some text (up to 20 characters maximum) and press “Send” to update the scrolling message.
With seven rows of LEDs, certain lowercase letters like ‘j’ or ‘g’ get clipped. Messages tend to look better typed in ALL CAPS.
To change the text color, type a number sign (#) followed by a hexadecimal color value; each digit is in the range 0-F (where A-F equal 10-15). If you’re familiar with HTML color values, it’s essentially the same format, e.g.:
#00ffff
You can also use three-digit hexadecimal color values. This has a smaller available palette, but the color fidelity of this project is limited anyway (more on that below).
Some common colors include:
#f00 Red #0f0 Green #00f Blue #ff0 Yellow (Red + Green) #0ff Cyan (Green + Blue) #f0f Magenta (Red + Blue) #fff White (Red + Green + Blue)
Primary colors (red, green, blue) will use less power, since only a single color within each RGB pixel is lit. White uses the most power; red, green and blue must all combine for this color.
I’ve successfully run the hat for over four hours using incredibly crappy dollar-store AA cells.
The message will freeze (not turn off) as the batteries approach depletion. This is the Arduino locking up as the voltage dips too low. It’s not harmful, just time to change the batteries.