Blync

There is funny little usb gadget called the Blync identified by VID: 0x1130, PID: 0x0001.

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It's a glowing RGB cube, but it has two defects for me:

  1. the driver is only available for Windows
  2. only 7 colors are available

Let's fix it.

Software hack

That's the easy part.

  1. Plug your Blync under Windows running in a virtual machine.
  2. Start Wireshark under the Linux host
  3. Dump USB packets
  4. Think
  5. Replay packets in Python

And VoilĂ : https://github.com/ticapix/blynux

Hardware hack

That is already funnier.

First, unscrew and remove the white top.

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You will notice 5 RGB LEDs.

The LEDs look like this one PLCC6 SMD, LED SMP6-RGB. The Polarity ID or Cathode mark is in the bottom left corner, so lower pins are the ground. They even put labels to ease the identification 🙂 LR, LG, LB for, respectively, the Red, Green, Blue pins.

Take a Leonardo Pro Micro (! check that the boot loader is already installed !)

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The Leonardo Pro Micro is a 5V board, but the LEDs need 2.1V for the Red and 3.3V for the Green and Blue so we need to add 3 resistors of value R=\frac{(V_{in}-V_{forward})}{I_{forward}} and keep in mind that I_{forward} is multiplied by 5.

In fact, the pins on the board can safely output only 40mA, which is less than the needed amount of 5*20mA=100mA. The proper solution would be to use a MOFSET like the IRF530.

I selected a resistor around 72 \Omega = \frac{(5-2.1)}{0.04} for red and 42 \Omega = \frac{(5-3.3)}{0.04} for green and blue.

Once this is done, solder the wires to the resistors to the PWM enable pins of the Leonardo. I choose pins 3, 5, 6.

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Upload some code via the Arduino IDE and plug it in a USB port. The cube should glow in this order: Red \rightarrow Yellow \rightarrow Green \rightarrow Cyan \rightarrow Blue \rightarrow Magenta \rightarrow Red.

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