It’s fair to say that right now is probably the worst possible time you could choose to design a new piece of hardware. Of course the reality is that, even in the middle of a parts shortage that’s driving the cost of many components through the roof (if you can even find them), we can’t just stop building new devices. In practice, that means you’ll need to be a bit more flexible when embarking on a new design — it’s like the Stones said: “You can’t always get what you want / But if you try sometime you’ll find / You get what you need”
Affordable and reliable cell phones have revolutionized the way we communicate over the last two decades or so, and this change was only accelerated by the adoption of the smartphone. This is all well and good if you’re living in a place with cellular infrastructure, but if you’re in more remote areas you’ll have to be a little more inventive. This text-based communications device, for example, lets you send text messages without all of that cumbersome infrastructure.
While [Arthur] didn’t create this project specifically for off-grid use, it’s an interesting project nonetheless. The devices use a physical QWERTY keyboard and a small screen, reminiscent of BlackBerry devices from the late 2000s (partially because they are actually using BlackBerry keyboards). One of the other goals for this project was low power consumption, and between polling the keyboard, the memory LCDs, and receiving and transmitting messages using LoRa, [Arthur] was able to get the current draw down to 12 mA.
Between the relatively common nRF52840 and SX1262 chips, plus the fact that [Arthur] made the schematics available, this makes for an excellent off-grid device for anyone who likes to drive off into the wilderness or lives far enough outside of town that cell phone reception is a concern.
Teaching people efficiently isn’t limited to transmitting material from one head to another — it’s also about conveying the principles that got us there. [Mara Bos] shows us a toolkit (Twitter,
nitter link) that you can arm your students with, creating a small playground where, given a set of constraints, they can invent and figure communication protocols out on their own.
This tool is aimed to teach digital communication protocols from a different direction. We all know that UART, I2C, SPI and such have different use cases, but why? Why are baud rates important? When are clock or chip select lines useful? What’s the deal with the start bit? We kinda sorta figure out the answers to these on our own by mental reverse-engineering, but these things can be taught better, and [Mara] shows us how.
Gently guided by your observations and insights, your students will go through defining new and old communication standards from the ground up, rediscovering concepts like acknowledge bits, bus contention, or even DDR. And, as you point out that the tricks they just discovered have real-world counterparts, you will see the light bulb go on in their head — realizing that they, too, could be part of the next generation of engineers that design the technologies of tomorrow.
One of the design requirements for the networks that evolved into the Internet was the ability to keep functioning, even if some nodes or links were disabled or destroyed in war. The packet-switched architecture that still powers today’s Internet is a direct result of that: if one link stops functioning, information is automatically re-routed towards its intended destination. However, with tech giants occupying increasingly large parts of the global internet, an outage at one of them might still cause major disruption. In addition, a large-scale power interruption can disable large parts of the network if multiple nodes are connected to the same grid.
Just six pieces of wood make up the birdhouse.
Enter the LoRa Birdhouse project by the Wellesley Amateur Radio Society that solves those two problems, although admittedly at a very small scale. Developed by amateur radio operators in eastern Massachusetts, it’s basically a general-purpose LoRa-based packet-switching network. As it’s based on open-source hardware and commonly available components, its design allows anyone to set up a similar network in their own area.
The network is built from nodes that can receive messages from their neighbors and pass them on towards their final destination. Each node contains a Semtech SX1276 transceiver operating in the 902-928 MHz band, which gets its data from an ESP32 microcontroller. The nodes are placed in strategic locations outside and are powered by solar panels to reduce their ecological footprint, as well as to ensure resilience in case of a power outage. To make the whole project even more eco-friendly, each node is built into a birdhouse that provides shelter to small birds.
Users can access the network through modified network nodes that can be hooked up to a PC using a USB cable. Currently, a serial terminal program is the only way to interact with the network, although a more user-friendly interface is being planned. FCC rules also require all users (except any avian residents) to be licensed amateur radio operators, and all traffic to remain unencrypted. Tests have shown that one kilometer between nodes can work in the right conditions, enabling the deployment of networks across reasonably large areas.
While the Birdhouse Network might not be a plug-and-play internet replacement in case of a nuclear apocalypse, it does provide an excellent system to experiment with packet-switching wireless network technology. We’ve seen similar LoRa-based network initiatives like Qmesh, Cellsol and Meshtastic, all of which provide some way to communicate wirelessly without requiring any centralized hardware.
[Elite Worm] had a problem; there had been two minor burglaries from a storage unit. The unit had thick concrete walls, cellular signal was poor down there, and permanent wiring wasn’t possible. He thus set about working on a burglar alarm that would fit his unique requirements.
An ESP32 is the heart of the operation, paired with a long-range LoRa radio module running at 868 MHz. This lower frequency has much better penetration when it comes to thick walls compared to higher-frequency technologies like 4G, 5G or WiFi. With a little coil antenna sticking out the top of the 3D-printed enclosure, the device was readily able to communicate back to [Elite Worm] when the storage unit was accessed illegitimately.
With an eye to security, the device doesn’t just warn of door open events. If signal is lost from the remote transmitter in the storage unit, perhaps due to an advanced adversary cutting the power, the alarm will also be raised. There’s still some work to be done on the transmitter side, though, as [Elite Worm] needs to make sure the door sensor is reliable under all conditions.
While wireless communications are unquestionably useful in projects, common wireless protocols such as WiFi and Bluetooth peter out after only a number of meters, which is annoying when your project is installed in the middle of nowhere. Moving to an LTE-based or similar mobile solution can help with the range, but this does not help when there’s poor cell coverage, and it tends to use more power. Fortunately, for low-bitrate, low-power wide-area networks (LPWAN) like e.g. sensor networks, there’s a common solution in the form of LoRaWAN, as in long-range wide area network (WAN).
The proprietary LoRa RF modulation technique that underlies LoRaWAN is based on Chirp Spread Spectrum (CSS). This modulation technique is highly resistant to channel noise and fading as well as Doppler shift, enabling it to transmit using relatively low power for long distances. LoRaWAN builds on top of the physical layer provided by LoRa to then create the protocol that devices can then use to communicate with other LoRa devices.
Courtesy of global LoRaWAN gateway and software providers such as The Things Industries and ThingSpeak, it’s possible even as a hobbyist to set up a LoRaWAN-powered sensor network with minimal cost. Let’s take take a look at exactly what is involved in setting up LoRaWAN devices, and what possible alternatives to LoRaWAN might be considered. Continue reading “Casually Chirping Into The World Of LoRaWAN”→
The LoRa radio protocol is well known to hardware hackers because of its Long Range (hence the name) but also its extremely low power use, making it a go-to for battery powered devices with tiny antennae. But what if the power wasn’t low, and the antenna not tiny? You might just bounce a LoRa message off the moon. But that’s not all.
The team that pulled off the LoRa Moonbounce consisted of folks from the European Space Agency, Lacuna Space, and the CA Muller Radio Astronomy Station Foundation which operates the Dwingeloo Radio Telescope. The Dwingeloo Radio Telescope is no stranger to Amateur Radio experiments, but this one was unique.
A radar image of the moon generated from LoRa Moonbounce
Operating in the 70 cm Amateur Radio band (430 MHz) meant that the LoRa signal was not limited to the low power signals allowed in the ISM bands. The team amplified the signal to 350 Watts, and then used the radio telescope’s 25 Meter dish to direct the transmission toward the moon.
The result? Not only were they able to receive the reflected transmission using the same transceiver they modulated it with — an off the shelf IOT LoRa radio — but they also recorded the transmission with an SDR. By plotting frequency and doppler delay, the LoRa transmission was able to be used to get a radar image of the moon- a great dual purpose use that is noteworthy in and of itself.
