Bit-Banged Ethernet On The Raspberry Pi Pico

August 26, 2022 by Dave Rowntree 30 Comments

Whilst the Raspberry Pi RP2040 is quite a capable little chip, on the whole it’s nothing really special compared to the big brand offerings. But, the PIO peripheral is a bit special, and its inclusion was clearly a masterstroke of foresight, because it has bestowed the platform all kinds of capabilities that would be really hard to do any other way, especially for the price.

Our focus this time is on Ethernet, utilizing the PIO as a simple serialiser to push out a pre-formatted bitstream. [kingyo] so far has managed to implement the Pico-10BASE-T providing the bare minimum of UDP transmission (GitHub project) using only a handful of resistors as a proof of concept. For a safer implementation it is more usual to couple such a thing magnetically, and [kingyo] does show construction of a rudimentary pulse transformer, although off the shelf parts are obviously available for this. For the sake of completeness, it is also possible to capacitively couple Ethernet hardware (checkout this Micrel app note for starters) but it isn’t done all that much in practice.

UDP is a simple Ethernet protocol for transferring application data. Being connection-less, payload data are simply formatted into a packet buffer up front. This is all fine, until you realize that the packets are pretty long and the bitrate can be quite high for a low-cost uC, which is why devices with dedicated Ethernet MAC functionality have a specific hardware serialiser-deserialiser (SERDES) block just for this function.

Like many small uC devices, the RP2040 does not have a MAC function built in, but it does have the PIO, and that can easily be programmed to perform the SERDES function in only a handful of lines of code, albeit only currently operating at 10 MBit/sec. This will cause some connectivity problems for modern switch hardware, as they will likely no longer support this low speed, but that’s easily solved by snagging some older switch hardware off eBay.

As for the UDP receive, that is promised for the future, but for getting data out of a remote device over a wired network, Pico-10BASE-T is a pretty good starting point. We’ve seen a few projects before that utilize the PIO to generate high speed signals, such as DVI, albeit with a heavy dose of overclocking needed. If you want a bit more of an intro to all things Pico, you could do worse than check out this video series we highlighted a while back.

Fried Desk Lamp Reborn: How To Use ESP8266 To Build Connected Devices

October 1, 2019 by Sean Boyce 9 Comments

Some hacks are born of genius or necessity, and others from our sheer ham-fisted incompetence. This is not a story about the first kind. But it did give me an excuse to show how easy it is to design WiFi-connected devices that work the way you want them to, rather than the way the manufacturer had in mind.

It started out as a sensible idea – consumer electronics in Vietnam have many different electric plug types for mains AC power: A, C, G, F, and I are fairly present, with A and C being most common. For a quick review of what all those look like, this website sums it up nicely. There are universal power adapters available of course, but they tend to fit my most common type (C) poorly, resulting in intermittent power loss whenever you sneeze. So I figured I should replace all the plugs on my devices to be A-type (common to those of you in North America), as it holds well in all the power bar types I have, mainly leftover server PDUs.

This was very straightforward until I got to my desk lamp. Being a fancy Xiaomi smart lamp, they had opted to hide a transformer in the plug with such small dimensions that I failed to notice it. So instead of receiving a balmy 12 volts DC, it received 220 volts AC. With a bright flash and bang, it illuminated my desk one final time.

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ESP8266 Upgrade Gives IKEA LEDs UDP Superpowers

May 27, 2019 by Tom Nardi 39 Comments

It can be difficult to resist the impulse buy. You see something interesting, the price is right, and even though you know you should do your research first, you end up putting it in your cart anyway. That’s how [Tobias Girstmair] ended up being the not-so proud owner of a LEDBERG RGB LED strip from IKEA, and what eventually pushed him to replace wimpy original controller with an ESP8266.

So what was the problem with the original controller? If you can believe it, it was incapable of producing white light. When IKEA says an LED is multi-color, they apparently mean it’s only multi-color. A quick check of the reviews online seem to indicate that the white version is sold as a different SKU that apparently looks the same externally and has confused more than a few purchasers.

Rather than having to pick one or the other, [Tobias] decided he would replace the original controller with an ESP-03, hoping that would give him granular enough control over the LEDs to coax a suitably white light out of them. He didn’t want to completely start from scratch, so one of the first decisions he made was to reuse the existing PCB and MOSFETs. Some handy test points on the PCB allowed him to hook the digital pins of the ESP right to the red, blue, and green LED channels.

Then it was just a matter of coming up with the software. To keep things simple, [Tobias] decided to create a “dumb” controller that simply sets the LED color and intensity according to commands it receives over a simplified UDP protocol. Anything beyond that, such as randomized colors or special effects, is done with scripts that run on his computer and fire off the appropriate UDP commands. This also means he can manually control his newly upgraded LEDBERG strips from basically anything that can generate UDP packets, such as an application on his Android phone.

It might not be the most robust implementation we’ve ever seen, but all things considered, it looks as though this modification could be a pretty good way to get some cheap network controlled RGB lighting in your life.

45-Year Old Nixie Calculator Turned UDP Server

July 15, 2016 by Elliot Williams 12 Comments

In this beautiful and well-documented reverse engineering feat of strength, [Eric Cohen] reverse-engineered a 1971 Singer calculator to gain control of the fabulous Nixie tubes inside. Where a lesser hacker would have simply pulled the tubes out and put them in a more modern housing, [Eric] kept it all intact.

Not even content to gut the box and toss some modern brains inside, he snooped out the calculator’s internal wiring, interfaced a Raspberry Pi to it, and overrode the calculator’s (860 Hz) bus system. With the Pi on the inside, controlling the Nixie tubes, he did what any of us would do: set up a UDP server and write an Android app for his phone to push ASCII data over to the former calculator. When it’s not running in its default clock mode, naturally.

All of this is extraordinarily well documented both on his website, in a slide presentation (PDF), and in video (embedded below). Our hats are tipped to the amazing attention to detail and fantastic documentation.

Now where is that Singer EC1117 calculator from 1971 that we’ve been saving for just such an occasion?

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Secret Listening To Elevator Music

May 24, 2016 by Elliot Williams 24 Comments

While we don’t think this qualifies as a “fail”, it’s certainly not a triumph. But that’s what happens when you notice something funny and start to investigate: if you’re lucky, it ends with “Eureka!”, but most of the time it’s just “oh”. Still, it’s good to record the “ohs”.

Gökberk [gkbrk] Yaltıraklı was staying in a hotel long enough that he got bored and started snooping around the network, like you do. Breaking out Wireshark, he noticed a lot of UDP traffic on a nonstandard port, so he thought he’d have a look.

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Digging HDMI Out Of UDP Packets

November 4, 2015 by Brian Benchoff 24 Comments

[Danman] was looking for a way to get the HDMI output from a camera to a PC so it could be streamed over the Internet. This is a task usually done with HDMI capture cards, either PCI or even more expensive USB 3.0 HDMI capture boxes. In his searches, [danman] sumbled across an HDMI extender that transmitted HDMI signals over standard Ethernet. Surely there must be a way to capture this data and turn it back.

The extender boxes [danman] found at everyone’s favorite chinese reseller were simple – just an Ethernet port, HDMI jack, and a power connector – and cheap – just $70 USD. After connecting the two boxes to his network and setting up his camera, [danman] listened in to the packets being set with Wireshark. The basic protocol was easy enough to grok, but thanks to the Chinese engineers and an IP header that was the wrong length, [danman] had to listen to the raw socket.

Once everything was figured out, [danman] was able to recover raw frames from the HDMI extenders, recover the audio, and stream everything to his PC with VLC. All the code is available, and if you’re looking for a way to stream HDMI to multiple locations on a network, you won’t find a better solution that’s this cheap.

How To Make Amazon Echo Control Fake WeMo Devices

July 16, 2015 by Rick Osgood 27 Comments

[Chris] has been playing with the Amazon Echo. It’s sort of like having Siri or Google Now available as part of your home, but with built-in support for certain other home automation appliances like those from Belkin WeMo and Philips. The problem was [Chris] didn’t want to be limited to only those brands. He had other home automation gear that he felt should work with Amazon Echo, but didn’t. That’s when he came up with the clever idea to just emulate one of the supported platforms.

The WeMo devices use UPnP to perform certain functions over the network. [Chris] wanted to see how these communications actually worked, so he fired up his laptop and put his WiFi adapter into monitor mode. Then he used Wireshark to start collecting packets. He found that the device detection function starts out with the Echo searching for WeMo devices using UPnP. The device then responds to the Echo with the device’s URL using HTTP over UDP. The Echo then requests the device’s description using that HTTP URL. The description is then returned as an HTTP response.

The actual “on/off” functionality of the WeMo devices is simpler since the Echo already knows about the device. The Echo simply connects to the WeMo over the HTTP interface and issues a “SetBinaryState” command. The WeMo then obliges and returns a confirmation via HTTP.

WeMo Echo — How Echo Communicates with WeMo Devices

[Steve] was able to use this information to set up his own WeMo “virtual cloud”. Each virtual device would have its own IP address. They would also need to have a listener for UDP broadcasts as well as an HTTP listener running on the WeMo port 49153. Each virtual device would also need to be able to respond to the UPnP discovery requests and the “on/off” commands.

[Chris] used a Linux server, creating a new virtual Ethernet interface for each virtual WeMo switch. A single Python script runs the WeMo emulation, listening for the UPnP broadcast and sending a different response for each virtual device. Part of the response includes the device’s “friendly name”, which is what the Echo listens for when the user says voice commands. Since the virtual WeMo devices are free, this allows [Chris] to make multiple phrases for each device. So rather than be limited to “television”, he can also make a separate device for “TV” that performs the same function. [Chris] is also no longer limited to only specific brands of home automation gear.

There’s still a long way to go in hacking this device. There’s a lot of hardware under the hood to work with. Has anyone else gotten their hands (and bench tools) on one of these?