PCIe For Hackers: The Diffpair Prelude

PCIe, also known as PCI-Express, is a highly powerful interface. So let’s see what it takes to hack on something that powerful. PCIe is be a bit intimidating at first, however it is reasonably simple to start building PCIe stuff, and the interface is quite resilient for hobbyist-level technology. There will come a time when we want to use a PCIe chip in our designs, or perhaps, make use of the PCIe connection available on a certain Compute Module, and it’s good to make sure that we’re ready for that.

PCIe is everywhere now. Every modern computer has a bunch of PCIe devices performing crucial functions, and even iPhones use PCIe internally to connect the CPU with the flash and WiFi chips. You can get all kinds of PCIe devices: Ethernet controllers, high-throughput WiFi cards, graphics, and all the cheap NVMe drives that gladly provide you with heaps of storage when connected over PCIe. If you’re hacking on a laptop or a single-board computer and you’d like to add a PCIe device, you can get some PCIe from one of the PCIe-carrying sockets, or just tap into an existing PCIe link if there’s no socket to connect to. It’s been two decades since we’ve started getting PCIe devices – now, PCIe is on its 5.0 revision, and it’s clear that it’s here to stay.

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Three Way LED Bulb Gives Up Its Secrets

You’ve probably seen three-way bulbs. You know, the ones that can go dim or bright with each turn of a switch. [Brian Dipert] wondered how the LED version of these works, and now that he tore one apart, you can find out, too. The old light bulbs were easy to figure out. They had two filaments, one brighter than the other. Switching on the first filament provided some light, and the second gave off more light. The final position lit both filaments at once for an even brighter light.

LED or filament, three-way bulbs have a special base. While a normal Edison-base bulb has the threaded part as the neutral and a center contact for the live wire, a three-way bulb has an extra hot contact ring between the threaded part and the center contact. Obviously, a compatible LED bulb will need this same interface, but will work differently inside.

Inside the LED, [Brian] found two rings of LEDs that took the place of the filaments. He was able to identify all the ICs and devices on the board except one, an MT7712S. If you can read Mandarin, we think this is the datasheet for it.

We weren’t sure what [Brian] would find inside. After all, you could just sense which contacts had voltage and dim the LEDs using PWM. It probably wouldn’t take any less circuitry. LED lighting is everywhere these days, and maybe they don’t all work the same, but you have to admit, using two strings of LEDs is reasonably faithful to the old-fashioned bulbs.

Sometimes LED bulbs are different depending on where you buy them. We were promised LED bulbs would never burn out. Of course, they do, but you can usually scrounge some LEDs from them.

Classic Gaming With FPGA And ATX

Playing classic games, whether they are games from the golden age of arcades or simply games from consoles that are long out of production, tends to exist on a spectrum. At one end is grabbing a game’s ROM file, finding an emulator, and kludging together some controls on a keyboard and mouse with your average PC. At the other is meticulously restoring classic hardware for the “true” feel of what the game would have felt like when it was new. Towards the latter end is emulating the hardware with an FPGA which the open-source MiSTer project attempts to do. This build, though, adds ATX capabilities for the retrocomputing platform. Continue reading “Classic Gaming With FPGA And ATX”