15

MQTT has to run over TCP/IP (I can't remember if it's actually in the spec or if just enough assumptions are made to make it so) but its sister protocol MQTT-SN can be run over nearly any protocol that can pass data, I've seen implementations in UDP and serial. Having said that I'm not sure what you gain by running either over BLE, BLE's built in ...


12

In general Bluetooth equipment always comes with a proprietary app for your phone... I think that if you want to have the control over your Bluetooth switches, you might want to take a look at Arduino Bluetooth modules and command relays on it to toggle normal lamps.


10

Arguably, you'd be better off doing a simple mapping of the data from BLE paradigms to MQTT, rather than trying to literally send MQTT over BLE. BLE generally exchanges data in the form of characteristics. These have various BLE-unique mechanisms for discovering value change that you may find useful. But they have a maximum data length of 20 bytes. It is ...


10

Reliable communications between digital devices requires some degree of signal processing to synchronize the data and the timing (clock). Adding relative motion between the transmitter and receiver can complicate the problem. You are probably aware that relative motion can impart Doppler frequency shifts. This also affects the timing of the bit stream. A ...


8

The problem is essentially one of receivers and of power. A "find my keys" type of beacon needs to be small enough to attach to your keychain and you probably don't want to have to regularly recharge the beacon (you wouldn't lose your keys if they're always in their charger) so that requires either: a passive technology without a battery. an active ...


8

Your challenge is handling the throughput demands with channel contention. Your devices are all close enough that you need to assume they are all potential interferers to each other so you will need to use a protocol that is robust to this - probably using some sort of coordination between devices to ensure they all take a fair slice of the channel. You ...


7

Latency vs Rate a low-latency (10 Hz) type of IoT application This is a conceptual error. Latency and Rate are largely independent. You could have a system which recorded thousands of readings per second, stored them on an SD card, and once a month someone visits the remote site, extracts the card, and mails it to you - that system would have a high ...


7

This is an unusual use-case where the data throughput which you require is really low - range and low power are the driving factors. This points in the direction of a low data-rate, narrow band protocol (or maybe one using a spreading code, such as GPS). Looking for long-range through walls, etc. implies a low RF frequency too, 433 MHz would probably be ...


7

This is a question on basic physics. Provided all parts of your network are moving at the same speed (give or take) then there is no impact of being in a moving reference frame (as we all are on Earth). For long-range radio protocols, there is a need to account for the round trip delay (transmit/receive/transmit synchronisation), and having one end of the ...


6

I would like to say that Yes, Bluetooth is a good candidate for indoor positioning. Depending on how good positioning you want, of course. If you have Bluetooth beacons scattered over your house it will probably be as simple as cell positioning - the beacon that last saw your key chain will be in the same room as the key chain. With one beacon per room, it ...


6

The closest to an answer that I can come to is this list of products supported by openhab. It doesn't identify which products use Bluetooth LE, but does identify products (indirectly) where the protocol is known.


6

Apple is keeping the technology it uses for AirPods under wraps, hence my answer is best attempt based on the information in public domain. Do both Airpods use Bluetooth technology? Yes, because Power efficiency that Airpods come with can be achieved via Bluetooth. Airpods are inter-operable with Android and Windows, this proves Apple has used standards ...


6

Have you looked at Web Bluetooth? This can be used to write to the the device without needing a native client app just to set the time. There is support in Chrome on most platforms and other browsers are adding support. I've been working on a device that uses Web Bluetooth to set the wifi details (the device is a clock that will use NTP to remain accurate ...


6

Since you don't intend to further communicate with the partner device I guess the precision of the set time is okay for you in a precision range of a few seconds. If you want to get more precise you'll have to take a lot more into consideration (delays, latency, lower level protocols and the like). In general BLE is a communications protocol, you can access ...


6

I would recommend some sort of mesh network, as obviously plain old WiFi or BT won't cover those distances. Zigbee is as good a candidate as any. For hardware, AdaFruit does some good wearables, although if everyone has a smartphone, you might as well use those. And, if you can figure out how to power it by battery, take a look at my answer to this ...


5

I think the only place that may have such a list would be the Bluetooth SIG as they will know what products are certified. Otherwise each profile might list a few examples of devices that implement it. The closest example of something similar I can think of is the ANT+ sig which hosts the following directory of devices/profiles https://www.thisisant.com/...


5

If two devices are already bonded and one of them is mains powered, you should be able to establish the connection in way less than 1 sec given that the mains powered device is constantly scanning or advertising, you're using directed advertisements, white listing, and low connection intervals in the first second. Another option is to keep the connection ...


5

SIMCOM SIM808 module seems to meet the requirements for your device. Bluetooth: compliant with 3.0+EDR Specification for GPS Receiver type 22 tracking /66 acquisition -channel GPS L1 C/A code Sensitivity Tracking: -165 dBm Cold starts : -147 dBm Time-To-First-Fix Cold starts: 30s (typ.) Hot starts: ...


5

The flic button from shortcut labs meets most (but not all) of your requirements. (not cheap and the light only comes on when the button is pushed iirc, but might be hackable/fixable at the firmware level) I think you might struggle to find something that meets your size requirements given a cr 2032 battery is 2cm diameter before you add any case and is 3....


5

Bluetooth (and pretty much every other transmission protocol in contrast to sensors like radar) are based on digital protocols. This means that the signals are both binary, and protected by error detection/correction codes. So long as the signal is strong enough that there are only a few errors in any one packet, the resulting sensor reading which is sent ...


4

For a stationary spinning wheel: when the antenna is mounted co-axially onto the hub of the wheel (assuming that the internal, typically folded BT antenna has been replaced with a straight wire antenna - an common hack done to improve BT signal strength), you'd be fine. For a moving wheel, like at a straight moving car, you will additionally have to ...


4

If you are planning to use cheap android tablets, you should do some survey to understand what technologies are possible options for authentication. Besides wifi and bluetooth connectivity, most of the tablets have USB OTG host connector and with some cable you should be able to attach USB authentication dongle. Or if security is not a big issue in your case,...


4

First you have to know that only one RSSI gives you nothing about distance. Because it may vary from device to device. To calculate distance you must know "calibrated" value. For example, RSSI value measured with this device on 1 meter distance. When you do that you will have 2 RSSI values: calibrated and current. Then use this formula: double Dist = pow(10....


4

The way Bluetooth direction finding works is described in this document. There are two scenarios: AoD (Angle of Departure): Sending device sends a "direction finding signal" Sending device is equipped with a "phased array antenna" Receiving device performs "IQ Sampling" AoA (Angle of Arrival): Sending device sends a "direction finding signal" Receiving ...


3

You can consider attaching pcProx® Plus RFID readers with the machines, 1 per machine. You can use RDR-80581AK8 SKU. It is powered by 5V external power supply and supports RS232 for sending data in ASCII format.


3

Possibly cheaper than a tablet would be a Raspberry Pi and a USB NFC reader or a NFC Hat. It's not clear what you mean by machine, but if you mean just another computer then both Linux and Windows will authenticate via NFC directly without the need for a tablet/pi/other device, just a USB NFC reader.


3

After a while of repetitively going through the code and my logic with no luck, I finally decided to probe the signals and check the timing of the 1-second silence preceding and succeeding the escape sequence. After checking the timing, it looked like the silence was less than 1-second, don't remember exactly how much. So I just changed the above code to the ...


3

Shameless plug In about a years time you can get an nRF91 + nRF52840 combo. LTE(CATM1 and NbIoT), GPS, BLE, USB, 802.15.4, etc, that uses a fraction of the power of current devices, and got plenty of µC-resources to spare.


3

If you add som randomness to the transmissions you'll be fine. Like 2min +/- random number between 1-10 seconds. You might not even need to do that. As some else have already mentioned the low frequency clocks used for time keeping are not that accurate and will have a random tolerance from the factory of typ +/- 50ppm, pluss temperature drift typ +/- 3ppm ...


3

If you are an experienced tinkerer, you might consider Goufalite’s solution. Personally, I think that market forces drive the commercially available solutions to be the best that they can currently be, but feel free to continue Googling for an answer to your question. With regard to some of the technologies that you mention: Bluetooth - is by far the ...


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