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

[Maohua Liu]

Dear Jason Kridner,

I want to know whether it is possible to use PRU-ICSS to control the built-in bluetooth module directly in OSD3358-512M-BAS. I just want the built-in bluetooth module to work as fast as possible because I want to use bluetooth module to realize time synchronization by wireless communication. So I want to use PRU-ICSS to circumvent OS, Stack and such kind of thing, and directly control the built-in bluetooth module in order to let this module work as fast as possible. Is that possible? If possilbe, what should I do in general? Is there something you want to suggest? Thank you!

B.R.

Maohua

[Robert Nelson]

> I want to know whether it is possible to use PRU-ICSS to control the built-in bluetooth module directly in OSD3358-512M-BAS. I just want the built-in bluetooth module to work as fast as possible because I want to use bluetooth module to realize time synchronization by wireless communication. So I want to use PRU-ICSS to circumvent OS, Stack and such kind of thing, and directly control the built-in bluetooth module in order to let this module work as fast as possible. Is that possible? If possilbe, what should I do in general? Is there something you want to suggest? Thank you!

what "built-in" bluetooth module? The OSD3358-512M-BAS, doesn't have
bluetooth...

https://media.digikey.com/Photos/Octavo/MFG_OSD3358-1GB-BAS_Image-3.jpg

Regards,

--
Robert Nelson
https://rcn-ee.com/

[Robert Nelson]

On Tue, Sep 11, 2018 at 1:43 PM Maohua Liu <Maohu...@uga.edu> wrote:
>
> Hey,
>
> Sorry for my mistake! So the bluetooth module is in fact integrated in the wifi module 'WL18MODGB', isn't ? Is it possible for me to use PRU-ICSS to control it? I want to use PRU-ICSS to directly control the bluetooth unit in order to get high real-time performance by circumventing the bluetooth stack, is it possible? Look forward to your reply!

Umm, the WL1835 is running it's own Bluetooth stack (the firmware we
provide for it on bootup), so while the WL1835 connects to the AM335x
over a simple usart, all the Major Bluetooth stuff is already
offloaded to the WL1835.. On the Linux side, we just interface to it
over Bluez..

So your statement: "in order to get high real-time performance by
circumventing the bluetooth stack" doesn't really fit, as you'd
basically implement a usart on the PRU-ICSS and yet, what... still go
thru bluez, looks more like a slow down....

[Maohua Liu]

Hey,

Sorry for my mistake! So the bluetooth module is in fact integrated in the wifi module 'WL18MODGB', isn't ? Is it possible for me to use PRU-ICSS to control it? I want to use PRU-ICSS to directly control the bluetooth unit in order to get high real-time performance by circumventing the bluetooth stack, is it possible? Look forward to your reply!

Best Regard,

Maohua

---

From: Robert Nelson <robert...@gmail.com>
Sent: Monday, September 10, 2018 6:46:26 PM
To: Beagle Board
Cc: Maohua Liu
Subject: Re: [beagleboard] Inquiry about whether it is possible to use PRU-ICSS to control the built-in bluetooth module in OSD3358-512M-BAS

 

[Maohua Liu]

Hey,

Sorry for my mistake!
I am now using BBB Wireless: http://beagleboard.org/black-wireless . So the bluetooth module is in fact integrated in the wifi module 'WL18MODGB', isn't ? Is it possible for me to use PRU-ICSS to control it? I want to use PRU-ICSS to directly control the bluetooth unit in order to get high real-time performance by circumventing the bluetooth stack, is it possible? Look forward to your reply!

Best Regard,

Maohua

---

From: Maohua Liu
Sent: Tuesday, September 11, 2018 11:43:23 AM
To: Robert Nelson; Beagle Board

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

[Maohua Liu]

Thank you very much!
 Your reply is really important for us. Or we will waste a lot of time.

B.R.

Maohua

---

From: Robert Nelson <robert...@gmail.com>
Sent: Tuesday, September 11, 2018 11:56:48 AM
To: Maohua Liu
Cc: Beagle Board

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

[Robert Nelson]

On Tue, Sep 11, 2018 at 4:29 PM WenZhan Song <wenzha...@gmail.com> wrote:
>
> 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..

[WenZhan Song]

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!

[drhun...@gmail.com]

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