Communication between two NRF51822 Beacon Kit

[Khalil Ahmad]

I'm going to write to inquire about Bluetooth Low Energy Device Beacon which will be smallest in size and can operate with coin cell battery and also able to communicate two devices with each other. I need following function to be performed by these two devices. one Ble will act as transmitter and other will be receiver and receiver will also connected with four Led's ( yellow,blue,green,red) as follows
1 - When one device will be in range of other it will Blink Yellow Led.
2 - When same device reached near (about 2-3 meters) to other it will Blink Blue LEd.
3 - When same device will reached 2 feet away from it it will blink Green LEd.
4 - When same device is going away from the range of other device Red Led will starts blinking.

Please let me know if you are able to provide this type of solution.

Regards,

Khalil Ahmad

[Einar Thorsrud]

Hi Khalil,

This is should be possible, but you should note that distance measurement via RSSI is quite inaccurate. So it only works if you don't need an accurate distance estimate (though you should be able to get something like "very close", "probably some distance away", and "probably far away". (Also, I suggest you consider an nRF52 device instead unless you plan to use the beacon kit as is. You can make any nRF52 design just as small as an nRF51 design.)

[Khalil Ahmad]

Is nRF52 and nRF51 are able to calculate distance ?

[Einar Thorsrud]

Not in any accurate way. The only option is to use RSSI to estimate distance, but that is not reliable.

[Khalil Ahmad]

is there any way or device to measure distance within accuracy of 1 meter ?

[Einar Thorsrud]

It is impossible to guarantee accuracy. You can certainly not get 1 meter accuracy on larger distances. But if the RSSI is very high, then you can perhaps do that. Example: you can say that a device that is 10 cm away is probably closer than 1 meter. But it is impossible to reliably say if a device is 5 or 10 meters away for instance. The RSSI will depend on many things. Even if you have calibrated the specific devices, it could be that one is held in a different way, different orientation, that there is an obstacle etc.

[Khalil Ahmad]

Thanks for your guidance.

can we get this information like, when some device gets into the range of other device, when one device gets off from the range of other device, and when one device has been reached at the other device ?

[Einar Thorsrud]

Hi,

Again, the only thing you get is the RSSI (of advertisement packets or packets when in a connection). How you use and interpret that is up to you.

[Khalil Ahmad]

Thanks. Thanks a lot.