How to increase acquisition frequency in real time? (TI Board F28379D)

Hello,

I'm using the TI Board F28379D with Simulink to make an acquisition of sinusoidal signal of 100Hz as frequency. Firstly, I try just to create just a signal with a sine wave block and send the signal to an scope to visualize using the external mode. I used a acquisition frequency of 10 kHz that should be sufficient, but when I'm using the external mode I haven't this acquisition frequency . I tried to use the serial communication without the external mode, but the result is similar.

Here the signal obtained using the external mode.

Anyone have a suggestion how to visualize this kind of signal?

Any help will be very appreciated.

Jessé Augusto

[Hassan Abouobaida]

I have a 20kHz frequency signal, I want to sample it at a frequency of 2MHz (100 samples per period), is it possible with DSP cards? if not, what is the appropriate solution in this case?

Thank you

Answer 1

[Antonin]

Hi Jessé,

In your previous post , you had set the SCIA baudrate to 9600, which is used for External mode. Make sure to increase the SCIA baudrate for better external mode performance. If using serial over USB, you can go up to 6 Mbps with any value, or exactly 9Mbps or exactly 12 Mbps. On the Launchpad, we can make it work with a desired baudrate of 12e6, though the closest achievable shows as 12.5e6. For some reason the controlCard is less permissive, by lowering the main CPU clock to 192.5 MHz we can achieve serial communication at 12.0313 Mbps on the controlCard, which works good for External mode.

Straight External mode allows you to watch signals at 5kHz (attached example: Extmode_straight.slx), you can try a higher frequency, but you will start seeing data drops. By buffering the data and putting the scope in a lower rate group, you can watch signals at 50kHz without data drops, which is what I show in the attached Extmode_buf.slx, I'm using the buffer block from the DSP System toolbox for that.

I hope it helps,

Cheers,

Antonin.

[Jesse Paixao]

Hi Antonin,

Thank you for your help. I could watch the signals at 50 kHz.

I could achieve this frequency with your model but I have one question. I'm using a model that use some ADC and PWM blocks, that consume a lot of memory and stop me of use the a large buffer block (size of 64 maximum).

Have you any suggestion to try in this case? I read something about combine the RAM memory to increase the capacity of storage, but I don't know if it's possible with the ControlCard.

Regards

Jessé Augusto

[Taimur Zaman]

did you get solution to your problem. i am using same model that contain 2 pwm blocks, and 1 ADC plus some integrators and mathematical equations for real time control of circuits. i am getting very low data with a very few samples.

[balapanuru obulapathi]

Hello Antonin,

Using buffer block gives he following error. Can you please rectify this?

[balapanuru obulapathi]

Error in 'Buck_closed_test/PI_Controller_ISR/Buffer': All sample times must be discrete. No continuous or constant sample times are allowed.

[Hassan Abouobaida]

Hello, thank you Antonin for your precious help.

To show the validity of the proposed method (in the External mode) and the possibility of acquiring a signal that can reach 50kHz, please insert in the examples you gave an analog to digital converter?

On the other hand, I find the following contradictions:

1- the frequency setting (Oscillator Clock) is 10 MHz then you have set 20 MHz

2- In another station, the recommended frequency for the communication between the COM port of connection between the DSP card and the Host PC is 115200b / S then you put 12Mb / s !!

Thank you

[e-mail]

Answer 2

[Venkatesh Chilapur]

Hi Jessé/Taimur,

You can use the 2 model approach when running computation intensive algorithms at high sample rate for data logging. We ship few examples that are based on this approach for data logging/streaming which is an alternate to the external mode.

Please check out the section 'Fast Serial Data Monitoring' at following page:

https://in.mathworks.com/help/supportpkg/texasinstrumentsc2000/examples/permanent-magnet-synchronous-motor-field-oriented-control.html

There is also a video talking about the same at:

https://www.mathworks.com/matlabcentral/fileexchange/61420-dc-dc-buck-converter-example

For operation details of the 2 model approach please check the following posts:

https://in.mathworks.com/matlabcentral/answers/353939-can-simulink-use-ti-c2000-launchxl-f28027f-or-f2808-to-monitor-a-analog-signal-200khz

https://in.mathworks.com/matlabcentral/answers/419321-what-is-the-idea-behind-data-processing-for-sci-communication-in-dc-dc-buck-converter-example

Hope this helps,

Regards,

Venkatesh C