Perfecting The Open Source RC Controller

Over the last few months we’ve seen an influx of homebrew RC controllers come our way, and we’re certainly not complaining. While the prices of commercial RC transmitters are at an all-time low, and many of them can even run an open source firmware, there’s still nothing quite like building the thing yourself. How else are you going to get exactly what you want?

For this entry into the 2019 Hackaday Prize, [Vitor de Miranda Henrique] is working on his own version of the ultimate open source remote control. His design follows some of the trends we’ve already seen in terms of outward design and hardware expandability, but also branches off into some new territory with features such as dual integrated displays.

Why does your controller need two displays? The top 4.3 inch TFT is linked up to a 5.2 GHz video receiver, which makes it perfect for controlling vehicles in “first-person” view, such as drones. The lower screen is a 2.8 inch touch screen from Adafruit, which is intended to be used for navigating through menus and options once the firmware is fully fleshed out.

Powering the controller is a ESP32 and dual MCP23017 GPIO expanders to connect up to the array of input devices available to the user. The current iteration of the controller has ten switches, two encoders, some buttons, and a pair of scroll wheels for good measure. Oh, and of course there are a couple of joysticks in the mix as well. All the devices terminate at a custom PCB in the back of the controller which looks to make modifying and adding input devices simple and neat.

We’ve previously seen the Alpha V1, an open source controller with a fairly similar setup, albeit without the dual displays. If even that one is a bit more complex than you’d like, you can always just do it with an Arduino.

The Great Ohio Key Fob Mystery, Or “Honey, I Jammed The Neighborhood!”

Hack long enough and hard enough, and it’s a pretty safe bet that you’ll eventually cause unintentional RF emissions. Most of us will likely have our regulatory transgression go unnoticed. But for one unlucky hacker in Ohio, a simple project ended up with a knock at the door by local authorities and pointed questions to determine why key fobs and garage door remotes in his neighborhood and beyond had suddenly been rendered useless, and why his house seemed to be at the center of the disturbance.

Few of us want this level of scrutiny for our projects, so let’s take a more in-depth look at the Great Ohio Key Fob Mystery, along with a look at the Federal Communications Commission regulations that govern what you can and cannot do on the airwaves. As it turns out, it’s easy to break the law, and it’s easy to get caught.

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Open Hardware E-Ink Display Just Needs An Idea

Its taken awhile, but thanks to devices like the Amazon Kindle, the cost of e-ink displays are finally at the point where mere mortals such as us can actually start using them in our projects. Now we’ve just got to figure out how to utilize them properly. Sure you can just hook up an e-ink display to a Raspberry Pi to get started, but to truly realize the potential of the technology, you need hardware designed with it in mind.

To that end, [Mahesh Venkitachalam] has created Papyr, an open hardware wireless display built with the energy efficiency of e-ink in mind. This means not only offering support for low-energy communication protocols like BLE and Zigbee, but keeping the firmware as concise as possible. According to the documentation, the end result is that Papyr only draws 22 uA in its idle state.

So what do you do with this energy-sipping Bluetooth e-ink gadget? Well, that part is up to you. The obvious application is signage, but unless you’re operating a particularly well organized hackerspace, you probably don’t need wireless dynamic labels on your part bins (though please let us know if you actually do). More likely, you’d use Papyr as a general purpose display, showing sensor data or the status of your 3D printer.

The 1.54 inch 200×200 resolution e-ink panel is capable of showing red in addition to the standard grayscale, and the whole thing is powered by a Nordic nRF52840 SoC. Everything’s provided for you to build your own, but if you’d rather jump right in and get experimenting, you can buy the assembled version for $39 USD on Tindie.

3D Printed Weather Station Gets A Wireless Upgrade

A weather station can be anything from a fun home science exercise, all the way up to a useful tool for planning and weather prediction. [Rob Ward] is one such person who has developed their own weather station, and it recently got a wireless upgrade.

We first featured [Rob]’s work back in 2018, noting that a largely 3D-printed weather station was a particularly useful tool for the home experimenter. The utility of this is now improved, with the addition of a 433 MHz wireless link from the weather sensors back to the base station. Over on Github, [Rob] does a great job of explaining the basics of the Manchester encoding scheme used, and has developed a system that can decode signals from Oregon Scientific weather stations, too.

[Rob] uses the weather station to report weather conditions at Lake Tyers Beach, providing useful information for anyone in the area who might be considering a visit to the coast. It’s not quite as fun as asking whoever’s around on the CB road channel, but it’s a darn sight more accurate for your trouble. Video after the break.

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Simple, Self-Contained LoRa Repeater In About An Hour

[Dave Akerman]’s interest in high-altitude projects means he is no stranger to long-range wireless communications, for which LoRa is amazingly useful. LoRa is a method of transmitting at relatively low data rates with low power over long distances.

Despite LoRa’s long range, sometimes the transmissions of a device (like a balloon’s landed payload) cannot be received directly because it is too far away, or hidden behind buildings and geography. In these cases a useful solution is [Dave]’s self-contained LoRa repeater. The repeater hardware is simple, and [Dave] says that if one has the parts on hand, it can be built in about an hour.

The device simply re-transmits any telemetry packets it receives, and all that takes is an Arduino Mini Pro and a small LoRa module. A tiny DC-DC converter, battery, and battery charger rounds out the bill of materials to create a small and self-contained unit that can be raised up on a mast, flown on a kite, or carried by a drone.

The repeater’s frequency and other settings can even be reprogrammed (using a small windows program) for maximum flexibility, making the little device invaluable when going hunting for landed payloads like the one [Dave] used to re-create a famous NASA image using a plastic model and a high-altitude balloon. Check out the details on the GitHub repository for the project and start mashing “add to cart” for parts at your favorite reseller.

Camera Sees Electromagnetic Interference Using An SDR And Machine Vision

It’s one thing to know that your device is leaking electromagnetic interference (EMI), but if you really want to solve the problem, it might be helpful to know where the emissions are coming from. This heat-mapping EMI probe will answer that question, with style. It uses a webcam to record an EMI probe and the overlay a heat map of the interference on the image itself.

Regular readers will note that the hardware end of [Charles Grassin]’s EMI mapper bears a strong resemblance to the EMC probe made from semi-rigid coax we featured recently. Built as a cheap DIY substitute for an expensive off-the-shelf probe set for electromagnetic testing, the probe was super simple: just a semi-rigid coax jumper with one SMA plug lopped off and the raw end looped back and soldered. Connected to an SDR dongle, the probe proved useful for tracking down noisy circuits.

[Charles]’ project takes that a step further by adding a camera that looks down upon the device under test. OpenCV is used to track the probe, which is moved over the DUT manually with the help of an augmented reality display that helps track coverage, with a Python script recording its position and the RF power measurements. The video below shows the capture process and what the data looks like when reassembled as an overlay on top of the device.

Even if EMC testing isn’t your thing, this one seems like a lot of fun for the curious. [Charles] has kindly made the sources available on GitHub, so this is a great project to just knock out quickly and start mapping.

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A DIY EMC Probe From Semi-Rigid Coax And An SDR

Do you have an EMC probe in your toolkit? Probably not, unless you’re in the business of electromagnetic compatibility testing or getting a product ready for the regulatory compliance process. Usually such probes are used in anechoic chambers and connected to sophisticated gear like spectrum analyzers – expensive stuff. But there are ways to probe the electromagnetic mysteries of your projects on the cheap, as this DIY EMC testing setup proves.

As with many projects, [dimtass]’ build was inspired by a video over on EEVblog, where [Dave] made a simple EMC probe from a length of semi-rigid coax cable. At $10, it’s a cheap solution, but lacking a spectrum analyzer like the one that [Dave] plugged his cheap probe into, [dimtass] went a different way. With the homemade probe plugged into an RTL-SDR dongle and SDR# running on a PC, [dimtass] was able to get a decent approximation of a spectrum analyzer, at least when tested against a 10-MHz oven-controlled crystal oscillator. It’s not the same thing as a dedicated spectrum analyzer – limited bandwidth, higher noise, and not calibrated – but it works well enough, and as [dimtass] points out, infinitely hackable through the SDR# API. The probe even works decently when plugged right into a DSO with the FFT function running.

Again, neither of these setups is a substitute for proper EMC testing, but it’ll probably do for the home gamer. If you want to check out the lengths the pros go through to make sure their products don’t spew signals, check out [Jenny]’s overview of the EMC testing process.

[via RTL-SDR.com]