measurement with oscilloscope

miguel senigagliesi

Other Parts Discussed in Thread: CC2650, CC2640

Hi all,

with my university i'm doing some measurement about the current consumption of cc2650 sensortag in connection mode, i modified tx power and other parameters like period sensor, i expected that changing period sensor of all the sensors the period on the screen change too, but it's not happened. It's always 50 ms in connection mode, why? i report a screen of the oscilloscope.

then is there a document that explain the form of the impulse? what does those peaks mean?

thank you for your answers.

over 9 years ago

0 Christin Lee over 9 years ago

TI__Guru 56405 points

Hi,

You can refer to the following application note we have regarding measuring BLE current consumption on CC2640.
www.ti.com/.../getliterature.tsp

0 miguel senigagliesi over 9 years ago in reply to Christin Lee

Prodigy 130 points

thank you for your answer, in the document's paragraph "5.3.3 connection event" it's written that there is a connection interval, ranging from 7.5 ms to 4 s, this isn't the sensor period that is adjustable using the ti app, right? otherwise i don't understand why the period that i saw in oscilloscope was always the same changing the sensor period via app.

0 Christin Lee over 9 years ago in reply to miguel senigagliesi

TI__Guru 56405 points

What you are seeing here is more like a recharge pulse. If it's a connection event, then you should be able to see clear TX/RX as what's shown in the documentation.

Can you use sniffer log to see what's the connection parameter you are at. The OS on the phone can decide what connection parameter is going to be used.

0 miguel senigagliesi over 9 years ago in reply to Christin Lee

Prodigy 130 points

With the oscilloscope i used a mean of 32 samples, because of this the impulse has that form (no many peaks), more specifically i got this:

that's similar to the last image of the document.

i changed the sensor period of all the sensors of the sensortag using the android app of the TI but there is no change at all, it's always 50 ms. Then i don't understand this: if i can change the sensor period of every sensor individually then if i choose different sensor period, in the oscilloscope i have to see a signal no more periodic, right?

0 Christin Lee over 9 years ago in reply to miguel senigagliesi

TI__Guru 56405 points

When you change the sensor period, you only change the period of sensor sampling. The connection interval has nothing to do with sampling period. You can sample as quick as you want, but if the connection interval which is controlled by the host(you phone) does not change, then you are wasting the power on the sensortag.

You can check what option you have for connection interval by using Connection Control Service.
For more information, please take a look of CC2650 sensortag user's guide.
processors.wiki.ti.com/.../CC2650_SensorTag_User's_Guide

0 miguel senigagliesi over 9 years ago in reply to Christin Lee

Prodigy 130 points

thank you, now i understand, so is there a method to set the connection interval for the low power? i searched on internet and i read that there is no ble api to do that.

0 Christin Lee over 9 years ago in reply to miguel senigagliesi

TI__Guru 56405 points

It varies from phone to phone. Again, you need to use connection control service to see what you can get from the phone and set it accordingly.

0 miguel senigagliesi over 9 years ago in reply to Christin Lee

Prodigy 130 points

i always used the app of the source code that i could download from site of TI and in that version there is not connection control service available, now i have the newest version taken from the play store and i see that there is! Is there a download available of the source code of this version?

0 Christin Lee over 9 years ago in reply to miguel senigagliesi

TI__Guru 56405 points

Due to open source distribution issues we will not be able to include more updates to the Android Source code. We have made stripped down examples that we have released here: git.ti.com/bluetooth-low-energy-android-project-zero-sample-code

0 miguel senigagliesi over 9 years ago in reply to Christin Lee

Prodigy 130 points

thank you! in the measurement that i did there is a standby current of 150/200 microampere, in the document that you give me there is a current of 1microampere, but i am measuring a sensortag with all the sensors active so i think that it's normal to see that result, right? i just want to measure the total power consumption, not only the ble consumption.

0 Christin Lee over 9 years ago in reply to miguel senigagliesi

TI__Guru 56405 points

It's normal to have high power consumption when the sensors are all active.

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measurement with oscilloscope