bluetooth low energy

46 Articles

Bluetooth As Proxy For Occupancy

December 13, 2023 by 59 Comments

During [Matt]’s first year of college, he found in a roundabout way that he could avoid crowds in the dining hall by accessing publicly available occupancy data that the dining hall collected. Presumably this was data for the dining hall to use internally, but with the right API calls anyone could use the information to figure out the best times to eat. But when the dining hall switched providers, this information feed disappeared. Instead of resigning himself to live in a world without real-time data on the state of the dining hall, he recreated the way the original provider counted occupancy: by using Bluetooth as a proxy for occupancy.

Bluetooth devices like smartphones, fitness sensors, and other peripherals often send out advertising packets into the aether, to alert other devices to their presence and help initiate connections between devices. By sniffing these advertising packets, it’s possible to get a rough estimate of the number of people in one particular place, assuming most people in the area will be carrying a smartphone or something of that nature. [Matt]’s Bluetooth-sniffing device is based on the ESP32 set up to simply count the number of unique devices it finds. He had some trouble with large crowds, though, as the first ESP32 device he chose didn’t have enough RAM to store more than a few hundred IDs and would crash once the memory filled. Switching to a more robust module seems to have solved that issue, and with a few rounds of testing he has a workable prototype that can run for long periods and log at least as many Bluetooth devices passing by as there are within its range.

While [Matt] hasn’t deployed this to the dining hall yet, with this framework in place most of the work has been done that, at least in theory, one of these modules could be easily placed anywhere someone was interested in collecting occupancy data. He has plans to submit his project to the university, to research the topic further, and potentially sell these to businesses interested in that kind of data. This isn’t an idea limited to the ESP32, either. We’ve seen similar projects built using the Raspberry Pi’s wireless capabilities that perform similar tasks as this one.

Thanks to [Adrian] for the tip!

Raspberry Pi Pico W Now Supports Bluetooth

June 15, 2023 by 11 Comments

What’s the best kind of upgrade a piece of consumer technology can get? A free one that doesn’t require you to do anything other than accept a new version of the software it’s running.

That’s precisely what every current (and future) owner of the Raspberry Pi Pico W just got with the addition of Bluetooth support to SDK 1.5.1. This is possible because the CYW43439 radio chipset used on the wireless version of the Pi Pico has always had Bluetooth capabilities, they just weren’t officially accessible from the C or MicroPython environments until now. In a corresponding blog post, [Eben Upton] explains that part of the delay was due to difficulties in getting both WiFi and Bluetooth connections to work simultaneously over the three-pin SPI bus that links the two chips on the board.

One thing that struck us as particularly interesting here is the use of BlueKitchen’s BTStack to provide support for both Bluetooth Classic and Low Energy profiles. This library is released under a modified version of the BSD 3-Clause license that otherwise specifically forbids commercial usage. That would be a problem for anyone who wanted to sell a gadget built around the Pico W, so Raspberry Pi Ltd negotiated — and presumably paid for — a special dispensation so commercial use is in the clear.

We should note that technically Bluetooth support was available in a beta state previously, albeit without this new license agreement made with BlueKitchen. Though anyone with a keen eye knew Bluetooth support was coming well before that, our own [Elliot Williams] called it when he first set eyes on the Pi Pico W back in 2022.

The BLE Datalogging Scale Of A Thousand Uses

March 29, 2023 by 7 Comments

Whether you’re making coffee or beer or complex chemicals, weighing your ingredients carefully and tracking them is key to getting good results. [Tech Dregs] decided to build a logging scale that would work seamlessly with his smartphone, and shared the design on YouTube.

The design begins with a Greater Goods manual electronic scale, which was chosen for its convenient design and 750 gram load cell. Once cracked open, [Tech Dregs] pulled out the original PCB to replace it with his own. Only the original buttons are used, with an Seed Xiao ESP32-C3 replacing the scale’s original brains. The original LCD screen was swapped out for an OLED display, and it also got a rechargeable lithium battery for better usability.

The real value of the project, though, is its communication capability. It’s able to talk to an Android smartphone over Bluetooth Low Energy. Thanks to a custom app, [Tech Dregs] is able to log weight readings from the scale over time and even graph them live on the smartphone. As a demonstration, the scale is used to log the weight of a cup as it fills with a shot of coffee, which should serve [Tech Dregs] well in his coffee automation projects.

We’ve seen bathroom scales hacked before, too, with similar connectivity upgrades.

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Using GitHub Actions To Brew Coffee

December 10, 2022 by 27 Comments

It’s getting harder and harder to think of a modern premium-level appliance that doesn’t come with some level of Internet connectivity. These days it seems all but the cheapest refrigerators, air purifiers, and microwaves include wireless capabilities — unfortunately they’re often poorly implemented or behind a proprietary system. [Matt] recently purchased a high-end coffee maker with Bluetooth functionality which turned out to be nearly useless, and set to work reverse-engineering his coffee maker and adapting it to work by sending commands from GitHub.

Since the wireless connectivity and app for this coffee maker was so buggy and unreliable, [Matt] first needed to get deep into the weeds on Bluetooth Low Energy (BTLE). After sniffing traffic and identifying the coffee maker, he set about building an interface for it in Rust. Once he is able to send commands to it, the next step was to integrate it with GitHub, so that filing issues on the GitHub interface sends the commands from a nearby computer over Bluetooth to the coffee maker, with much more reliability than the coffee maker came with originally.

Using [Matt]’s methods, anyone stuck with one of these coffee makers, a Delonghi Dinamica Plus, should be able to reactivate the use of its wireless functionality. While we’d hope that anyone selling a premium product like this would take a tiny amount of time and make sure that the extra features actually work, this low bar seems to be oddly common for companies to surmount. But it’s not required to pick up an expensive machine like this just to remotely brew a cup of coffee. You can do that pretty easily with a non-luxury coffee maker and some basic wireless hardware.

An infographic showing a tap with a sensor and a flow meter display

2022 Hackaday Prize: Sensible Flow Helps You Keep Track Of Your Water Usage

October 17, 2022 by 15 Comments

Safe, clean drinking water is a scarce resource that shouldn’t be wasted. But it’s not always easy to see how much you’re using when you turn on the tap: is it one liter a minute? Is it ten? How much do you actually use when washing your hands or brushing your teeth? If you’d like to get some hard data on your water usage, have a look at [Josh EJ]’s Sensible Flow project. It contains designs for a set of sensors that measure your water consumption and a convenient little display that shows the total amount consumed.

The most obvious way of measuring water consumption is to install an off-the-shelf flow meter onto your pipe, which is something that Sensible Flow supports. But probably the most interesting part of the project is a design for a non-invasive flow sensor that you can simply attach to any type of tap. This sensor contains a nine-axis inertial measurement unit (IMU) that detects how far you’ve twisted, turned or tilted the handle, and uses that information to estimate the amount of water flow. You will need to perform an initial calibration step using a timer and measuring cup, but you won’t have to rip open your plumbing just to keep track of your water usage.

Both types of sensors are powered by a coin cell battery that is estimated to work for about one year, thanks to a power-efficient Arduino Pro Mini and a BlueTooth Low Energy (BLE) module to communicate with the base station. The base station plugs into a wall socket and shows the total water consumption on a small one-inch OLED display. STL files for the enclosures are available on the project page, along with detailed circuit diagrams that show how all the parts are connected.

We’ve seen several water flow measurement systems for home use, such as this neat ESP8266-based shower water monitor. If you prefer just a simple visual reminder to turn off the tap, have a look at this LED gadget.

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A small round NRF51822 board glued to the underside of a mailbox lid, with a small vibration sensor attached

Check Your Mailbox Using The AirTag Infrastructure

May 30, 2022 by 32 Comments

When a company creates an infrastructure of devices, we sometimes subvert this infrastructure and use it to solve tricky problems. For example, here’s a question that many a hacker has pondered – how do you detect when someone puts mail into your mailbox? Depending on the availability of power and wireless/wired connectivity options, this problem can range from “very easy” to “impractical to solve”. [dakhnod] just made this problem trivial for the vast majority of hackers, with the FakeTag project – piggybacking off the Apple’s AirTag infrastructure.

This project uses a cheap generic CR2032-powered NRF51822 board, sending the mailbox status over the FindMy system Apple has built for the AirTag devices. For the incoming mail detection, he uses a simple vibration sensor, glued to the flap lid – we imagine that, for flap-less mailboxes, an optical sensor or a different kind of mechanical sensor could be used instead. Every time someone with a FindMy-friendly iPhone passes by [dakhnod]’s mailbox, he gets an update on its status, with a counter of times the sensor has been triggered. [dakhnod] estimates that the device could run for up to a year on a single battery.

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TapType: AI-Assisted Hand Motion Tracking Using Only Accelerometers

May 14, 2022 by 16 Comments

The team from the Sensing, Interaction & Perception Lab at ETH Zürich, Switzerland have come up with TapType, an interesting text input method that relies purely on a pair of wrist-worn devices, that sense acceleration values when the wearer types on any old surface. By feeding the acceleration values from a pair of sensors on each wrist into a Bayesian inference classification type neural network which in turn feeds a traditional probabilistic language model (predictive text, to you and I) the resulting text can be input at up to 19 WPM with 0.6% average error. Expert TapTypers report speeds of up to 25 WPM, which could be quite usable.

Details are a little scarce (it is a research project, after all) but the actual hardware seems simple enough, based around the Dialog DA14695 which is a nice Cortex M33 based Bluetooth Low Energy SoC. This is an interesting device in its own right, containing a “sensor node controller” block, that is capable of handling sensor devices connected to its interfaces, independant from the main CPU. The sensor device used is the Bosch BMA456 3-axis accelerometer, which is notable for its low power consumption of a mere 150 μA.

User’s can “type” on any convenient surface.

The wristband units themselves appear to be a combination of a main PCB hosting the BLE chip and supporting circuit, connected to a flex PCB with a pair of the accelerometer devices at each end. The assembly was then slipped into a flexible wristband, likely constructed from 3D printed TPU, but we’re just guessing really, as the progression from the first embedded platform to the wearable prototype is unclear.

What is clear is that the wristband itself is just a dumb data-streaming device, and all the clever processing is performed on the connected device. Training of the system (and subsequent selection of the most accurate classifier architecture) was performed by recording volunteers “typing” on an A3 sized keyboard image, with finger movements tracked with a motion tracking camera, whilst recording the acceleration data streams from both wrists. There are a few more details in the published paper for those interested in digging into this research a little deeper.

The eagle-eyed may remember something similar from last year, from the same team, which correlated bone-conduction sensing with VR type hand tracking to generate input events inside a VR environment.

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