How accurate is the proximity feature in BLE, can I detect if two BLE are touched tougether?
Electronic – Can bluetooth LE detect a touch using proximity
bluetoothbluetooth low energy
Related Solutions
BLE is very unsuitable for even medium bandwidth streaming (audio or video), because it is designed for transfer of few and small data packets with lots of sleeping time in between. This is why it is called 'low energy' and not 'low power' - it reduces the amount of picojoules per bit for small packets with respect to competing standards. Other standards mostly use more power not because they have less efficient radios, but because at least the receiver is constantly powered up even when there are comparatively huge lulls in radio traffic, and because a significant portion of the transferred bits are not payload but instead overhead - protocol headers, checksums, even just blanking space. BLE eliminates most of these unnecessary power draws. But mind you, it doesn't magically improve power use of the transceivers when they are active. And when doing video transfer, the transceivers are constantly powered up. You lose the biggest advantage of BLE.
This design choice reduces overhead to essentially as little as you like, but also makes it that it does not have any streaming facilities built-in natively like packet recombination, delayed acknowledgement and asynchronous transfers. You actually don't have anything built in, BLE is as raw as you can get to a wireless interface, barring maybe nRF24 and TI CC2x00. As a result, you'll need to do this in software (either on a microcontroller or on your user device) and this uses incredibly much more energy than if you use a purpose-built protocol with hardware facilities for this like Bluetooth 3.0 EDR or WiFi.
This leads to the somewhat counterintuitive notion that once you start getting into audio-type data rates and above, Bluetooth Low Energy becomes, depending on your implementation, about 2x less efficient than Bluetooth 3.0, and when you get into the megabit range it is substantially less efficient than WiFi. This is why WiFi exists - that and arguably wireless range, although nowadays transceivers for both standards are very much equivalent. WiFi just has optional MIMO and diversity.
So even when not taking into consideration the - at least for video - very restrictive bandwidth and range limits that Bluetooth imposes, you may not achieve the goal of low power video transfer with this method.
A Smart device can be a master or a slave. It is important to understand that when a Smart device communicates with a SmartReady device, they're both using the 'low energy' subset of Bluetooth v4.0, and therefore either can be master or a slave, depending on your implementation.
Generally, being Smart or SmartReady is a hardware feature, while being master or slave is a connection feature, so the two are not related.
I hope this helps.
Best Answer
The "proximity" feature in BLE is actually based on signal strength of the packets it receives (RSSI).
The RSSI changes very little with distance when the devices are far away, and disturbances play a large role in the RSSI value making it a very unreliable as a direct distance measure in the far field.
However when you bring two devices close to each other (<1m), the RSSI starts to grow exponentially and therefore the different disturbance play little role in the RSSI value compared to the distance.
While it is impossible to detect millimetre differences, i.e. plastic bits actually touching vs 1mm apart, you can get about 10cm accuracy when the antennas are near to each other. Please do note that this will be somewhat dependent on the antenna design of both devices, meaning to get very accurate you would need to measure the exact setup with the devices.