It’s Time for M.2 to Shine

Some people like to deck out their computer with LEDs and fancy case mods to make it a showpiece. These additions are meant to be seen, of course, so no one really wants to hide their bling on their M.2 cards, which are generally hidden away deep inside the machine. Well, aside from bitluni, anyway, who thinks it is time for M.2 cards to shine — literally. For reasons unknown, he decided to build an LED matrix into a M.2 expansion card.

As odd as this sounds, you do not have to be the type of person that likes to light a lamp and put it under a basket to appreciate this little LED matrix. It really does add a major cool factor to any machine — especially single-board computers that leave their expansion boards exposed, or machines with glass windows in their cases. Sometimes you just have to make your wild ideas a reality to see how it will turn out.

Since nothing quite like this has been done before, bitluni had his work cut out for him in figuring out how to interface a custom LED matrix with a computer via an M.2 connector. After doing some digging, he found a cool little chip that translates between PCIe and serial interfaces. Given that M.2 connectors support a PCIe interface, that should be enough to do most of the heavy lifting.

With this knowledge, a custom PCB was designed. It was populated with the PCIe-to-serial chip and a CH32V208 RISC-V microcontroller that controls an array of 240 RGB LEDs. After populating the board, bitluni inserted it into a single-board computer with great anticipation and… nothing! Some basic troubleshooting showed that the PCIe-to-serial chip was running way hotter than expected, which is never a good thing.

That led to a long debugging session, and ultimately it was discovered that the send and receive lines got mixed up. So the circuit design was fixed and a new board was ordered. Temperatures looked good on the new board, and it was recognized by the OS of the computer, so bitluni programmed the microcontroller and the LEDs were blinking as expected. Sweet success!

To make the board more fun and usable, a web browser-based tool was created to send drawings to the LED matrix. It can even be done remotely, so your friends can have some fun (or mischief) with it as well.

At this point, the only question is: what is next for the M.2 LED matrix. I hope the answer is a round of Doom, but it looks like we will have to hang in there a while before we find out.