cc2540 keyfob: problem in connection when oscilloscope probe is connected

Omkar Karmalkar

Hello,

I am trying to measure the power consumption of keyfob while transmitting button notifications. I attached USB dongle and connected to keyfob using BTool. Then I enabled button notifications by writing 01:00 to handle 0x0048. I started getting button notifications in BTool Everything works fine until I connect oscilloscope probe to the resistor which is in series with the power supply. This setup is provided in application note AN 092 Measuring Bluetooth® Low Energy Power Consumption. When I connect the probe the keyfob disconnects and no more packets are exchanged until the rpobe is removed and the connection is reestablished from BTool.

What could be the reason?

I am following exact same setup as given on page 5 in AN 092 here: http://www.ti.com/lit/an/swra347a/swra347a.pdf

Keyfob is running its original KeyfobDemo firmware.

over 10 years ago

0 Willis1 over 10 years ago

TI__Genius 17975 points

It is difficult to say exactly what is causing this, the only thing that I can think is that something in your setup is limited the current draw by your power supply, and could be causing the chip to brown out and reset.

0 Omkar Karmalkar over 10 years ago in reply to Willis1

Prodigy 50 points

Thanks Willis.

I did the exact same setup described in the application not given in first post. I checked it thoroughly and repeatedly but I am not able to find the fault.

0 J Lindh over 10 years ago

TI__Guru 57865 points

Hi Omkar,

How do you power the keyfob? Could you try with a battery? I know that there may be errors with ground if connected to a power source.

Best Regards

Joakim

Bluetooth®︎

Bluetooth forum

cc2540 keyfob: problem in connection when oscilloscope probe is connected