Datadrops in External Mode with Ti Launchpad at sampling rate of 20kHz.

Hi all,

I’m trying to read sensor data from my TI LaunchPad F28069M in External Mode to analyze the behavior of a PI controller in real time.

When I increased the sampling frequency from 10 kHz to 20 kHz, I noticed significant data drops in the logged signals. In the attached screenshot, the left side shows 10 kHz (no problem), and the right side shows 20 kHz (with data drops).

As I understand, I need External Mode to see the signals that the ADC block is reading. I set up External Mode with serial communication using the USB cable delivered with the board.

My questions:

1. Are there any options to increase the sampling rate without data drops?
2. Is there a limit to the sampling frequency when using External Mode with serial communication?
3. I wonder wether the PI-Controller works right in these Phases with no new datapoints and it is simple a problem with transfering the Data from the Launchpoad to the Computer or even the Controller dosent get the live data and is also effected by the data drops.

System details:

• MATLAB/Simulink version: 24a
• Add-ons: latest versions
• Baud rate: 5,625,000
• Hardware: TI LaunchPad F28069M
• External Mode: serial over USB
• Model type:

I’m new to microcontrollers and have limited experience with baud rates, serial communication, and related settings, so any guidance would be very helpful.

Thank you in advance!

Answer 1

[Leepakshi]

Hi Tim,

The error coccurs mostly because sampling time of blocks are not synced. We need to give a check for board clock frequency as well. And there is alos a chance that there can be a cable or hardware issue.

Moreover, when using External Mode over serial communication, the data transfer rate is limited by the baud rate and USB protocol, so increasing the sampling frequency from 10 kHz to 20 kHz often exceeds the bandwidth, causing data drops. This does not affect the PI controller execution on the hardware, it continues to run at the specified sample time, but only impacts the data logging to the host.

Try contacting Mathworks support if this doesn't solve the issue:

https://www.mathworks.com/help/matlab/index.html

Hope it helps!

[Tim]

Hi Leepakshi,

first of all thank you for your answer it is really helpful for me.

So if i get you right there is no problem for the Launchpad to work with higher frequenzies only the communication to the PC via External Mode is the Problem.

i dont really get what you mean with your second sentence (We need to give a check for your board clock freqeuncy as well)