is BlueTooth link Correct Solution for this ...

[VinayDand]

Hello,

   

My question will be:

   

Will Blue Tooth Link will be the correct solution for the following application?

   

Application:

   

One Common receiver in a room of approximate 30 x 30 Ft. size.

   

There will be approximate 60 Nos. Transmitter in the room.

   

Each transmitter will have 4 buttons on them without any other external peripherals / LEDs etc.

   

When any one of the 4 button is pressed, it should transmit the button number along with unique transmitter id to the common receiver, which receives the code and stores the button choice information for that transmitter.

   

Possibility of simultaneous transmission by any of (or all of) 60 users should be taken care of.

   

How to achieve robustness of detection of button choice among multiple transmitter to a common receiver.

       

Additional wish list / specs.:

   

Low power - long lasting battery life for each transmitter (CR2032 coin cell battery operation)

   

Capsense button detection (saves on mechanical button costs)

   

Common receiver connects to a PC on USB link - as a CDC serial device, for data transfer.

   

Lowest cost for each transmitting device.

       

Like to have ideas, suggestions towards implementing above application, suitability of BLE technology for the same. Failing which what kind of RF link solution may be used in the application. (IR optical link is not a preferred solution)

       

Regards,

   

Vinay

[Bob_Marlowe · Accepted solution]

Sounds doable, but not quite easy. PSoC4 BLE is good for a single point-to-point connection. Recently there was a project shown that polled for connections one after the other. The used time-slice was in the range of one second which would mean your 60 buttons can be polled within one minute. I'm not quite sure how much the time-slice could be reduced. The distance seems ok for BLE.

       

Bob

[ETRO_SSN583]

If the simultaneous press only has to be recorded time synchronous to

   

a central clock answer is yes as each BT device can manage a key press

   

in uS (the edge detect) and bounce in/out a key press in ~ 200 mS for a

   

mechanical key. So if a broadcast from central of time in order to time

   

stamp the key press sounds like not issue. Remaining issue is latency

   

to receive all nodes status. And the continuing popularity of BT means there

   

will be other devices in room, like cell phones, activity wrist bands, all using

   

the airspace, but not responding to your profile.

       

Most likely your latency will be dominated by the time you allot for all node

   

status reporting, eg. the time window you allot humans for response.

       

Then of course the polling latency.

       

Regards, Dana.

[HeLi_263931]

It might be an idea  to transmit the last button press (when and which button) in the advertising data of the peripherals. That should be faster to collect than when you connect to each device.

[VinayDand]

Hello,

       

Thanks Bob, Dana, Hli for suggesting design ideas.

       

As I am a Newbie on Bluetooth design.I would like to know:

       

Suppose in design, all slaves units start advertising (that a button is pressed) and Master is making connection to each slave one by one to retriev button pressed data for that slave.

       

Initially - worst case - all 60 slaves are advertising, till master makes connection to them individually and they stop advertising on transfer of data using response to scan request by master.

       

Are 60 channels advertising simultaneously allowed and tolerable in Bluetooth scenario? Interference / collision issue?

       

Approximate estimate on time to establishing connection and getting scan report from each slave by a single master, sort of polling latency period.

       

Is there a mechanism to tell all slaves at once that, now you start scanning keys and advertise them when a key press is detected.

       

Regards,

   

Vinay

   

[ETRO_SSN583]

This might shed some light -

           

          http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&sqi=2&ved=0CEMQFjAH&url=http%3A%2F%2F...

       

Shows latency to connect -

       

          http://www.summitdata.com/blog/ble-overview/

       

Regards, Dana.

[Anonymous]

 For better low power performance, you may also refer the AN for BLE Low Power:

   

AN 92584: http://www.cypress.com/?rID=110007

[ETRO_SSN583]

More ref material that might be of use -

               

http://www.cypress.com/?id=5509 100 Projects in 100 Days with Bluetooth

   

http://www.cypress.com/?rID=102512     AN91445 - Antenna Design Guide

   

http://www.cypress.com/?rID=102505     AN94020 - Getting Started with PRoC™ BLE

   

http://www.cypress.com/?rID=110007     AN92584 - Designing for Low Power and Estimating Battery Life for BLE Applications

   

http://www.cypress.com/?rID=109900     AN91162 - Creating a BLE Custom Profile

   

http://www.cypress.com/?rID=110107     AN91184 - PSoC 4 BLE - Designing BLE Applications

   

http://www.cypress.com/?rID=102504     AN91267 - Getting Started with PSoC® 4 BLE

           

http://www.cypress.com/?rID=107332     AN95089 - PSoC® 4/PRoC™ BLE Crystal Oscillator Selection and Tuning Techniques

               

Regards, Dana.

[VinayDand]

Thanks BMAH and Dana for the pointers.

       

Regards,

   

Vinay