Graph Variables - Motorware

Rushi Jariwala

Other Parts Discussed in Thread: MOTORWARE

I am facing some issues while plotting variables on the graph. I am using Lab11 of motorware where I have added my code to read ADC values from sin-cos encoder. The oscilloscope shows a perfect sine wave whereas the graph shows some distortion (attached image). I think it has something to do with the buffer size and acquisition rate. I am not sure though.

This is the code:

void Graph(_iq data0, _iq data1, _iq data2, _iq data3)
{
if(Buffer_Counter>=Buffer_Size)
{
Buffer_Counter = 0;
}
Buffer0[Buffer_Counter] = data0;
Buffer1[Buffer_Counter] = data1;
Buffer2[Buffer_Counter] = data2;
Buffer3[Buffer_Counter] = data3;
Buffer_Counter++;
return;
}

I have define buffer size as:

#define Buffer_Size 1000

Please let me know what is the issue.

over 6 years ago

0 Yanming Luo over 6 years ago

TI__Guru** 117080 points

Recommend you use PWMDAC to monitor the sensing signal. The Graph tool can't show the continuous period waveform since the length of the buffer is not equal to the integer times of the sampling points.

0 Rushi Jariwala over 6 years ago in reply to Yanming Luo

Expert 1225 points

Thanks Yanming for the reply.

I will use PWMDAC in that case. Just for curiosity, I want to understand what do u mean by: "since the length of the buffer is not equal to the integer times of the sampling points."

In my case, buffer length is 1000. How do I calculate the sampling points? The display data size is 1000 - is it not the number of sampling points?

What is the impact of "since the length of the buffer is not equal to the integer times of the sampling points."

0 Rushi Jariwala over 6 years ago in reply to Rushi Jariwala

Expert 1225 points

Hi Yanming,

PWMDAC works. But I still prefer the graph method.

Would like to understand what is the issue with the graph method?

And if we can have some solution around it?

0 Yanming Luo over 6 years ago in reply to Rushi Jariwala

TI__Guru** 117080 points

You save the data in the array in a cycle loop, so the waveform data will be not continuous if the loop ends and starts again. For example, you save a new data in Buffer0[0] while the loop end, but the Buffer0[0] is not the sampling data in front of Buffer0[1] of the waveform.

You may implement moving data within the arrays if the CPU bandwidth is enough.

0 Rushi Jariwala over 6 years ago in reply to Yanming Luo

Expert 1225 points

Hi Yanming,

I now understand the issue (I should have thought of this on my own though).

Thanks.

0 Yanming Luo over 6 years ago in reply to Rushi Jariwala

TI__Guru** 117080 points

OK. That's fine. Let's know if you have any further questions.

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Graph Variables - Motorware