Maximum notification frequecy

[BLE_Full_Stack]

Hello All,

Chip :  nrf52832

Mobile App : BLE scanner

Requirement : We want to transfer 20 Bytes(or more) at every 8 ms. Is it possible?

I have tested it :

No of Bytes : 12
Connection Interval : 7.5 ms
Data transfer @ 1 sec            : Done, No data loss
Data transfer  @ 500 ms         : Done, No data loss
Data transfer @100 ms          : Done , No data loss
Data transfer @ 40 ms          : Done , No data loss
Data transfer @ 10 ms          : Data transfer was possible, but we were not manage to check it to BLE Scanner, it was stopped.Application is running but i can't see data in BLE Scanner

Please can anyone confirm on this?Is it possible for 8 ms?

[DaleScott]

Hey, I'm not an expert in this area, but doing the math, if connection interval is 7.5 ms and want data transfer complete by 8 ms, that requires 20 Bytes to be transferred in 0.5 ms.  20/0.5x10-3 = 20,000/.5 = 40,000 bytes/sec = 320,000 bps or 0.32 Mbps.

From infocenter.nordicsemi.com/.../nRF52832_PS_v1.0.pdf

"The RADIO contains a 2.4 GHz radio receiver and a 2.4 GHz radio transmitter that is compatible with Nordic's proprietary 1 Mbps and 2 Mbps radio modes in addition to 1 Mbps Bluetooth® low energy mode."

Since 0.32 Mbps is less than 1 Mbps, this suggests to me that the device is designed to handle 20 Bytes in the 0.5 ms window. I would expect it to be limited to less than 1/0.32 x 20 = 62.5 Bytes at the 8 msec point.

[DaleScott]

While the nRF52832 appears to have the bandwidth to meet your 20 Byte requirement, it seems reasonable that there are lots of overhead protocol activities which could hog up the timeline and make it not work. So, my answer is incomplete because I don't know what kind of handshakes go on when you run the BLE Scanner. Hope my answer helped some though.

[haakonsh]

The nRF52832 with S132 can easily handle 20 byte payload at 7.5ms connection intervals, given its only connected to a single BLE link. The bottleneck in your application is most likely the mobile phone as Anroid/iOS limits the connection interval to 20ms i believe. 

Why do you need 8ms latency, what is your use-case?