CC2640R2F-Q1: BLE ToF_version 3.10

Jens G

Part Number: CC2640R2F-Q1

Hi TI Team,

My setup is like follow: Master and passive are 30cm away from each other The slave has a distance of 1m at the start of the calibration (is this needed for the new software version?) First RTLS Monitor shows some results around +-1m. After some time we can see that the distance shown from Master and Passive are different(ca. 5m) And in the time I written down my text here, the signal goes down to -10m.How can this be possible with time of flight calculation?

Now I have the following questions:

What is necessary to change in the setup for better performance?
Is it necessary to have the slave in 1m distance for calibration?
Why 3 devices?Which task has each device?
Is it possible to do the measurement with 2 devices?
What needs to be done for calibration? What happen? Is it possible to manually calibrate the system? If yes, how?
Why looks the signal of master and passive different?
What needs to be done if I don’t want to use the API and only want to use the Com-Port (helps for better understanding what will happen in background)

Thanks and best regards

Jens

over 6 years ago

0 J Lindh over 6 years ago

TI__Guru 57865 points

Hi Jens,

Thanks for evaluating our RTLS offering. I assume you are using SDKv3.10 and you can refer to this SLA for more in depth information;

Please note that the primary feature of ToF is security, not distance measurement. Assigning one of the experts to follow up on the technical enquiries, but here are some initial answers,

Jens G said:
What is necessary to change in the setup for better performance?

We are continuously making improvements to the robustness with the ToF feature, what you can do right now are two things. The first is related to the environment, making sure to reduce the potential interferers and multipath-enablers such as metal objects etc. The second would be to start combining AoA and RSSI data into the distance measurement result, to get more accurate result over time.

Jens G said:
Is it necessary to have the slave in 1m distance for calibration?

I think you should have 0m (devices close to each other)

Jens G said:
Why 3 devices?Which task has each device?

Master and Slave creates a Bluetooth low energy connection that the Passive device follows. This is why you see two results, one from Master and one for Passive.

Jens G said:
Is it possible to do the measurement with 2 devices?

Yes, that should be possible

0 Jens G over 6 years ago in reply to J Lindh

TI__Expert 3245 points

Hi Guys,

regarding "What is necessary to change in the setup for better performance?"

"We are continuously making improvements to the robustness with the ToF feature, what you can do right now are two things. The first is related to the environment, making sure to reduce the potential interferers and multipath-enablers such as metal objects etc. The second would be to start combining AoA and RSSI data into the distance measurement result, to get more accurate result over time."

Would it help to use more passives? If I use the RTLS Monitor, is in the Master diagram the calculation of the passives included?

What does it look with the topic 5-7? (manually calibration, number of samples, different signal behavior of master slave, What commandos do I need for own GUI tool that I can calculate the results of all nodes if not included into the master signal.)

Please also take a look into this bullets.

Thanks and best regards

Jens

0 Jens G over 6 years ago in reply to Jens G

TI__Expert 3245 points

Any Feedback? There are still open questions!

0 Sean2 over 6 years ago in reply to Jens G

TI__Mastermind 33460 points

Hi Jens,

What is necessary to change in the setup for better performance?
1. My best assumption is that you have a very bad calibration. This is supported by the fact that you have results down to -10m.
2. A good calibration is vital to good ToF performance.
Is it necessary to have the slave in 1m distance for calibration?
1. No, there is a calibrate API that takes calibration distance as a parameter.
Why 3 devices?Which task has each device?
1. This is explained extensively in both the User's Guide and SimpleLink Academy
Is it possible to do the measurement with 2 devices?
1. Yes, for TOF this is possible, with AoA no.
What needs to be done for calibration? What happen? Is it possible to manually calibrate the system? If yes, how?
1. The calibration procedure takes a given number of samples per frequency at a fixed distance. These are averaged and then subsequent will have the calibration value subtracted from it. (which is why you can have -10m as results if the calibration is bad)
2. Calibration is immediately triggered before ToF is started.
Why looks the signal of master and passive different?
1. What do you mean? The passive doesn't transmit at all during ToF, instead just listening.
2. If you mean the results themselves, then they are two different devices that are in a different spatial location, therefore their ToF results will vary.
What needs to be done if I don’t want to use the API and only want to use the Com-Port (helps for better understanding what will happen in background)
1. I would estimate that rewriting the RTLS host application that runs on the PC would take several weeks of effort. I don't recommend this.
2. Instead, I recommend using the Python module which will handle sending and receiving of commands for you, but allows you to tweak the parameters and APIs them selves.
3. This python module is the subject of the SimpleLink academy that I have linked above.

As a general note, while the SDK uses 1m calibration distance by default it is best to use 0m (keeping the boards only a few cm apart to prevent RF saturation). You can orient the boards as shown in the picture below.

It is recommended to calibrate outdoors with the boards laid in the grass.

Bluetooth®︎

Bluetooth forum

CC2640R2F-Q1: BLE ToF_version 3.10