[beagleboard] Inquiry about whether it is possible to use PRU-ICSS to control the built-in bluetooth module in OSD3358-512M-BAS

Robert,

Thank you for replying our questions! To be clear, what we intend to do is: we want to design a time synchronization protocols among a group of BBBWs using the bluetooth radio in BBBW, with the goal to achieve 10 us accuracy. Thus, we want to program PRU to send and receive bluetooth messages with low-level timestamping for that accuracy. The hypothesis is that ARM with Linux perhaps has too much uncertainty and delay while PRU can reduce that.

and "how" exactly is the PRU going to reduce that? It doesn't control
the radio directly...

Is this possible? If not, do you happen to know any mature way to achieve 10 us accuracy with Bluetooth or WiFi radio. I currently use GPS but it does not work well indoor.

PS, If you look at:

http://blog.bluetooth.com/exploring-bluetooth-5-how-fast-can-it-be

It would be better to just use a Bluetooth 5 usb dongle..

Regards,

Thanks for reply! But Bluetooth speed itself is not a decision factor of time sync accuracy as time sync message is small, we only concern about the delay/jitter caused by Linux OS - or perhaps it is not a concern at all? We will find out. Thanks!

Hi WenZhan,
The only access you have to the Bluetooth inside the WL183x device is via an HCI interface over UART. There is no specification I am aware of that would allow you to infer time of Rx/Tx at the bluetooth physical layer from the time the HCI interface delivers information.

If you are looking to do time sychronisation within a network then the wifi part of WL183x has the option to do that
http://processors.wiki.ti.com/index.php?title=WL18xx_Clock_Synchronisation_with_NTP_in_SDK3

This uses the Access Points Wi-Fi beacon to synchronise all the stations connected to the AP. It was done on BBGW using TI’s SDK.

You would need to merge some of the specific time synchronisation code from TI’s R8.7 driver release into a mainline kernel to get it working on a current kernel.
Iain