CC2538DK: Sniffer not reading correct RSSI values

Hi Tessa,

We will look into this and get back you as soon  as possible.

Thanks,

Alexis

Hi,

Can you explain the test setup in some detail?

When you say "the board says -45dBm" is the board connected with a coaxial cable?

The sniffer can be oriented in anyway as long as it receives the packet.

The point of the sniffer is to analyse packet content and not do any RF measurement or qualification.

If you want to do some RF performance tests you should use SmartRF studio and co-axially connected RF paths.

Thanks,

Hello!

I'm currently not using a coaxial cable. I just used the boards straight out of the box, and the average RSSI is displayed on the board's LCD. I know that the sniffer receives actual RSSI values, not the average RSSI values, but if the board's LCD is printing an average of -45dBm, and the sniffer is receiving -29dBm and -30dBm, something is not right. I've used the SmartRF Studio to obtain the RSSI values, and it looks to me like the sniffer is the odd one out.

On an added note, is there a way to obtain the RSSI values from SmartRF studio with only one board connected to the PC and the other board completely wireless? I've successfully done tests with both boards connected to a PC running the SmartRF Studio, but Ideally I want at least one board (ideally both) wireless. 

Thank you!

Hi,

RSSI values may vary depending on the orientation of antenna and interaction of the surroundings.

Please explain your setup in second paragraph. You can have both boards connected to the PC (via SmartRF Studio) and still communicate wirelessly.

Packet RX pane of the Studio shows both average RSSI as well as RSSI for each received packet.

Regards

Hello!

My set current up is as follows: I have a CC2538DK board (receiver) connected to a PC at a fixed location. The another PC is connected to the other CC2538DK board (transmitter), and this PC/CC2538DK is moved from one distance to another (for example, 1 meter, 2 meters, 3 meters, etc.) to obtain RSSI readings. Both PCs have SmartRF Studio running on them in order to obtain the results in a text file. The antennas are pointed at each other, with the boards both facing each other (I wasn't sure if the antennas are omni-directional or directional so I wanted to play it safe).

Basically, I want to be able to take RSSI readings and have the results saved (like the text file format of the SmartRF Studio method I explained above), but with one or zero devices connected to a PC. I though the sniffer was a good way of doing this (I also saw there is a Micro SD card slot on the boards. Perhaps this is an option?). I am open to any other suggestions you may have :)

I have done testing various locations, including an open field, where the closest structure was at least 100 meters away, which I think is as close to theoretical free space as I will get.

Thank you! 

- Tessa

Hi,

You can save data with "Dump Data to File" option present at the bottom in the Packet RX pane of studio.

The antenna is fairly omni directional. See the documentation here for inverted-F antenna: http://www.ti.com/tool/CC-ANTENNA-DK2

Thanks

Hello!

To be honest, that doesn't help me. I explained in my previous message that I'm already obtaining the data in a text file (I should have used the term "Data Dump", so maybe that's my bad), and I'm looking for an alternative to this since the SmartRF Studio software requires both CC2538DK devices to be connected to a computer running the software in order for the data dump to be successful.

Basically, I need a method of obtaining accurate RSSI readings where the transmitter and receiver are not connected to a PC running the SmartRF Studio software. This is why I looked into the packet sniffer that came with the development kit (packet sniffer number CC2531), however it gave very inaccurate RSSI readings. I need help with how I can increase this accuracy, as well as how the sniffer should be positioned in relation to the CC2538DK devices, which is why I'm considering abandoned the idea of using the packet sniffer all together. Is there any way to improve the accuracy of the packet sniffer's RSSI readings (like a setting or something)? Or is there another alternative method of obtaining data where the two CC2538DK devices are not both connected to a computer? I noticed there is a MicroSD card slot on the SmartRF06 board, is it possible to save the data dump information using a MicroSD card?

Thank you,

- Tessa

Hi,

Yes, you can save data on SD card but for that you have to write your own software using the driverlib APIs.

In the foundation firmware https://www.ti.com/tool/CC2538-SW you will find example software for SD card in the bsp\srf06eb_cc2538 folder.

You have to incorporate the SDcard example in the receiver code extracted from PER test software available here www.ti.com/.../swrc272.

The sniffer reports the RSSI of its own receiver and not that of CC2538 under test.

Regards,

Thank you for the information! It doesn't sound like the sniffer will work for my applications, but I will look into the SD card slot. I would rather not write my own software if possible (just takes up time haha), so is there any other method of obtaining RSSI results?

Thank you very much!

- Tessa