BLE advertising : Minimum packet length ?

[Altron]

Hello,

I'm a beginner on BLE protocol and i would like to send data during approximately 4us,stop it during the same time and transmit signal again during 4us and so on.

This mean that advertising packet will be less than 1byte (8us). Is it possible to do make fragmentation ?

Help me please, i need to this on smartphone application.

[Kenneth]

Hi,

No, in BLE the minimum connection interval is 7.5ms. So you need to buffer up data into 7.5ms chunks.

Best regards,
Kenneth

[Altron]

Thanks,

But i don't want to establish connection between 2 devices. I just need to make advertising during 7us or less and stop it after as a pulse signal.

[AmbystomaLabs]

BLE broadcasts a preamble and sync word prior to the packets as do most wireless protocols.

These alone are longer than 8usec.

[Kenneth]

I understand what you want to do, but it is not possible. For any given packet there is typically this timing:

startup radio : 150us

preamble and address (2Mbps): 20us

packet content (2Mbps): (4us for each 8bit)

crc (2Mbps): 8us

Then you typically want to switch direction to receive an ack (not counting if there may be retransmissions due to packet loss).

So in total it may take around 500us putting it all together sending one data packet in a proprietary way (you can't do it this fast in BLE).

Best regards,
Kenneth

[Altron]

Thanks :)

As i said i don't want to establish connection between 2 devices. Do you have a idea of how can i turn on a sensor with a perdiodical signal at 120KHz through the smartphone, no matter the communication protocol (WIFI or BLE) and the transmitted data frame ?

The receiver (sensor) can only detect this signal.