Creating a 3G Raspberry Pi Smartphone

It’s hard to believe, but the Raspberry Pi has now been around long enough that some of the earliest Pi projects could nearly be considered bonafide vintage hacks at this point. A perfect example are some of the DIY Raspberry Pi smartphone projects that sprung up a few years back. Few of them were terribly practical to begin with, but even if you ignore the performance issues and bulkiness, the bigger problem is they relied on software and cellular hardware that simply isn’t going to cut it today.

Which was exactly the problem [Dylan Radcliffe] ran into when he wanted to create his own Pi smartphone. There was prior art to use as a guide, but the ones he found were limited to 2G cellular networks which no longer exist in his corner of the globe. He’s now taken on the quest to develop his own 3G-capable Pi smartphone, and his early results are looking very promising.

Inside the phone, which he calls the rCrumbl, [Dylan] has crammed a considerable amount of hardware. A Raspberry Pi 3B+ with attached Adafruit touchscreen LCD is the star of the show, but there’s also a Pi camera module, battery charging circuit, and Adafruit FONA 3G modem (which also provides GPS). Powering the device is a 2500 mAh 3.7V battery, which reportedly delivers a respectable 8 to 12 hour runtime.

The case is 3D printed, and [Dylan] says it took a long time to nail down a design that would fit all of his hardware, keep things from shifting around, and still be reasonably slim. Obviously DIY phones like this are never going to be as slim as even the chunkiest of modern smartphones, but the rCrumbl looks fairly reasonable for a portable device. We especially like the row of physical buttons he’s included along the bottom of the screen, which should help with the device’s usability.

Speaking of usability, that’s where [Dylan] still has his work cut out for him. The existing software he’s found won’t work on 3G, so he’s going to have to come up with his own software stack to provide a proper phone interface. As it stands he’s made a call on the rCrumbl using command line tools, but while that might score you some extra geek points at the next hacker meetup, it’s not exactly going to fly for daily use. He mentions he would love to talk to any developers out there that would like to team up on the software side of the project.

We’ve covered one of the 2G Pi smartphones in the past, and of course the ZeroPhone is a very interesting project if you don’t mind the “dumb phone” interface. But if you’re looking for something that’s fairly close to commercial devices in terms of usability, you might just want to roll your own Android phone.

GSM Phone Network At EMF Camp Built on Raspberry Pi and LimeSDR

The Electromagnetic Field 2018 hacker camp in the UK will have its own GSM phone network, and as we have already covered its badge will be a fully-functional GSM phone. This is as far as we are aware a first in the world of badges, and though it may not be a first in hacker camp connectivity it is still no mean achievement at the base station side. To find out more we talked to two of the people behind the network, on the radio side Lime Microsystems‘ [Andrew Back], and on the network side Nexmo‘s developer advocate, [Sam Machin].

There are sixteen base stations spread around the site, of which each one is a Raspberry Pi 3 B+ with a LimeSDR Mini. Development of the system was undertaken prior to the release of the Raspberry Pi Foundation’s PoE board, so they take a separate 24V supply which powers the Pi through a DC-to-DC converter. This arrangement allows for a significant voltage drop should any long cable runs be required.

On the software side the base stations all run the Osmocom (Open Source Mobile Communications) cellular base station infrastructure package. It was a fine decision between the all-in-one Osmocom NITB package and the fully modular Osmocom, going for the former for its reliability. It was commented that this would not necessarily be the case at a future event but that it made sense in the present. It appears on the network as a SIP phone system, meaning that it can easily integrate with the existing DECT network. Let’s take a look at how the network operates from the user side, and the licencing loophole that makes everything possible.

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Particle Introduces New Hardware, Adds Mesh Support

Particle, makers of the WiFi and Cellular IoT modules everyone loves, is introducing their third generation of hardware. The Particle Argon, Boron, and Xenon are Particle’s latest offering in the world of IoT dev boards, and this time they’re adding something amazing: mesh networking.

New Particle boards named Argon, Boron, and XenonThe three new boards are all built around the Nordic nRF52840 SoC and include an ARM Cortex-M4F with 1MB of Flash and 256k of RAM. This chip supports Bluetooth 5 and NFC. Breaking the new lineup down further, the Argon adds WiFi with an ESP32 from Espressif, the Boron brings LTE to the table with a ublox SARA-U260 module, and the Xenon ditches WiFi and Cellular, relying only on Bluetooth, but still retaining mesh networking. This segmentation makes sense; Particle wants you to buy a ton of the Xenon modules to build out your network, and use either the Argon or Boron module to connect to the outside world.

The form factor of the boards conforms to Adafruit Feather standard, a standard that’s good enough, and much better than gigantic Arduino shields with offset pins.

Of particular interest is the support for mesh networks. For IoT solutions (whatever they may be), mesh networking is nearly a necessity if you have a sufficient number of nodes or are covering a large enough area. The technology going into this mesh networking is called Particle Mesh, and is built on OpenThread. While it’s a little early to see Particle’s mesh networking in action, we’re really looking forward to a real-world implementation.

Preorder pricing for these boards sets the Argon module at $15, the Boron at $29, and the Xenon at $9. Shipping is due in July.

Behind the Scenes at a Pair of Cell Sites

Those who fancy themselves as infrastructure nerds find cell sites fascinating. They’re outposts of infrastructure wedged into almost any place that can provide enough elevation to cover whatever gap might exist in a carrier’s coverage map. But they’re usually locked behind imposing doors and fences with signs warning of serious penalty for unauthorized access, and so we usually have to settle for admiring them from afar.

Some folks, like [Mike Fisher] aka [MrMobile], have connections, though, and get to take an up close and personal tour of a couple of cell sites. And while the video below is far from detailed enough to truly satisfy most of the Hackaday crowd, it’s enough to whet the appetite and show off a little of what goes into building out a modern cell site. [Mike] somehow got AT&T to take him up to a cell site mounted in the belfry and steeple of the 178-year old Unitarian Church in Duxbury, Massachusetts. He got to poke around everything from the equipment shack with its fiber backhaul gear and backup power supplies to the fiberglass radome shaped to look like the original steeple that now houses the antennas.

Next he drove up to Mount Washington in New Hampshire, the highest point in the northeast US and home to a lot of wireless infrastructure. Known for having some of the worst weather in the world and with a recent low of -36°F (-38°C) to prove it, Mount Washington is brutal on infrastructure, to which the tattered condition of the microwave backhaul radomes attests.

We appreciate the effort that went into this video, but again, [Mike] leaves us wanting more details. Luckily, we’ve got an article that does just that.

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Emergency Cell Tower on a Budget

Cell phone towers are something we miss when we’re out of range, but imagine how we’d miss them if they had been destroyed by disastrous weather. In such emergencies it is more important than ever to call loved ones, and tell them we’re safe. [Matthew May] and [Brendan Harlow] aimed to make their own secure and open-source cellular network antenna for those occasions. It currently supports calling between connected phones, text messaging, and if the base station has a hard-wired internet connection, users can get online.

This was a senior project for a security class, and it seems that the bulk of their work was in following the best practices set by the Center for Internet Security. They adopted a model intended for the Debian 8 operating system which wasn’t a perfect fit. According to Motherboard their work scored an A+, and we agree with the professors on this one.

Last year, the same SDR board, the bladeRF, was featured in a GSM tower hack with a more sinister edge, and of course Hackaday is rife with SDR projects.

Thank you [Alfredo Garza] for the tip.

Hackaday Prize Entry: A Mobile Electric Gate

Electric gates can be an excellent labor-saving device, allowing one to remain in a vehicle while the gate opens and closes by remote activation. However, it can become somewhat of a hassle juggling the various remotes and keyfobs required, so [bredman] devised an alternative solution – controlling an electric gate over the mobile network.

20 years ago, this might have been achieved by wiring a series of relays up to the ringer of a carphone. These days, it’s a little more sophisticated – a GSM/GPRS module is connected to an Arduino Nano. When an incoming call is detected, the gate is opened. After a 3 minute wait, the gate is once again closed.

[bredman] suffered some setbacks during the project, due to the vagaries of working with serial on the Arduino Nano and the reset line on the A6 GSM module. However, overall, the gate was a simple device to interface with, as like many such appliances, it has well-labelled and documented pins for sending the gate open and close signals.

[bredman] was careful to design the system to avoid unwanted operation. The system is designed to always automatically close the gate, so no matter how many times the controller is called, the gate will always end up in a closed state. Special attention was also paid to making sure the controller could gracefully handle losing connection to the mobile network. It’s choices like these that can make a project much more satisfying to use – a gate system that constantly requires attention and rebooting will likely not last long with its users.

Overall, it’s a great project that shows how accessible such projects are – with some carefully chosen modules and mastery of serial communications, it’s a cinch to put together a project to connect almost anything to the Internet or mobile networks these days.  For a different take, check out this garage door opener that logs to Google Drive.

Particle Electron – The Solution To Cellular Things

Just over a year ago, Particle (formerly Spark), makers of the very popular Core and Particle Photon WiFi development kits, released the first juicy tidbits for a very interesting piece of hardware. It was the Electron, a cheap, all-in-one cellular development kit with an even more interesting data plan. Particle would offer their own cellular service, allowing their tiny board to send or receive 1 Megabyte for $3.00 a month, without any contracts.

Thousands of people found this an interesting proposition and the Electron crowdfunding campaign took off like a rocket. Now, after a year of development and manufacturing, these tiny cellular boards are finally shipping out to backers and today the Electron officially launches.

Particle was kind enough to provide Hackaday with an Electron kit for a review. The short version of this review is the Electron is a great development platform, but Particle pulled off a small revolution in cellular communications and the Internet of Things

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