CCS/TMS320F28027: Methods for obtaining different frequencies of sine wave

ADDAGUDURU SURYA KIRAN

Intellectual 770 points

Part Number: TMS320F28027

Tool/software: Code Composer Studio

Sir/Madam,

Can anyone suggest me how to change the frequency of sine wave formed from lookup table.

over 5 years ago

0 Keith Barkley over 5 years ago

Guru 35680 points

Read it back at a different rate.

If the rate is constant, you need to either add or subtract points.
i.e., Say you have a 512 element table with one cycle, by making it a 1024 element table you will halve the frequency.

0 ADDAGUDURU SURYA KIRAN over 5 years ago in reply to Keith Barkley

Intellectual 770 points

Sir,

Thanks for the reply. I didn't understand what you are saying. Please can you explain me in detail. One more thing is that i tried with CPU timers by changing the time in micro seconds. But when plotting it in CCS I am not finding any difference between 50Hz and 100Hz.

0 Tomasz Kocon over 5 years ago in reply to ADDAGUDURU SURYA KIRAN

Guru 26200 points

Hi,

lets assume that you have 1 ms ticks and the 1000 elements lookup table.
Each tick you send next value from the table.
During 1s you would send all values from the table (indexes from 0 to 999) and you would get 1 Hz sine ware.
Second scenario.
Each tick you send the parity even values (0, 2, 4, ..., 998) from the table would give you 2 Hz sine wave.

0 desouza over 5 years ago in reply to Tomasz Kocon

TI__Guru**** 168422 points

Hi,

>>But when plotting it in CCS I am not finding any difference between 50Hz and 100Hz.

The time correlation in the CCS graph tool is completely arbitrary. It will plot the entire buffer and by default it will show the value in the Y axis and the sample count in the X axis. When setting the Graph Properties, you can specify the parameters "Sampling Rate Hz" and "Time Display Unit". The Graph will automatically calculate the time for you.

Regards,

Rafael

0 ADDAGUDURU SURYA KIRAN over 5 years ago in reply to desouza

Intellectual 770 points

HI,
Sorry for my late response and Thanks for the response. Actually I did the same thing by adjusting the sampling rate. I am getting correct waveform for the 50 Hz but the same waveform is also being displayed for the 100 Hz .
Explanation:
I changed sampling rate in the settings then i checked for 50 Hz and 100Hz. In 20 milli seconds i am getting only one cycle for both 50Hz and 100Hz . That is wrong I have to get 2 cycles in 20 milli seconds for 100Hz. I am unable to do that.

0 Keith Barkley over 5 years ago in reply to ADDAGUDURU SURYA KIRAN

Guru 35680 points

You need to change the *program* not the graphing tool display.

0 ADDAGUDURU SURYA KIRAN over 5 years ago in reply to Keith Barkley

Intellectual 770 points

Hi Keith,
Thanks for your reply.Can you just describe in brief how to change the program as i was not understanding where to change in the program. Otherwise could you suggest any material so that it could be helpful in solving.

0 Tomasz Kocon over 5 years ago in reply to ADDAGUDURU SURYA KIRAN

Guru 26200 points

Go to User's Guide section:

http://www.ti.com/product/TMS320F28027/technicaldocuments

Your question is not related to CCS.

Go to Piccolo forum, if not you will wait forever.

0 ADDAGUDURU SURYA KIRAN over 5 years ago in reply to Tomasz Kocon

Intellectual 770 points

Can I open New thread linking the present thread in C2000 forum??

0 Tomasz Kocon over 5 years ago in reply to ADDAGUDURU SURYA KIRAN

Guru 26200 points

You can copy link to this thread and paste it in a new post on C2000 forum.
Yes,
please do it.

0 desouza over 5 years ago in reply to ADDAGUDURU SURYA KIRAN

TI__Guru**** 168422 points

Hi,

Better yet. Simply click ont he button "Ask a related question" on the top right corner of this thread. It will automatically link to this thread.

Regards,

Rafael

0 Tomasz Kocon over 5 years ago in reply to desouza

Guru 26200 points

Hello Rafael,

I could not find the way to "ask a related question" and post it in a different forum.
Is it possible?

0 desouza over 5 years ago in reply to Tomasz Kocon

TI__Guru**** 168422 points

Tomasz,

When I clicked on the icon, the screen below is shown. Does the highlighted drop-down menu not show for you?

Regards,

Rafael

0 Tomasz Kocon over 5 years ago in reply to desouza

Guru 26200 points

Rafael,

CCS was the only option.

0 desouza over 5 years ago in reply to Tomasz Kocon

TI__Guru**** 168422 points

Tomasz,

It may have been a glitch yesterday. We did several tests today without a problem. Can you retry?

Regards,
Rafael

0 Tomasz Kocon over 5 years ago in reply to desouza

Guru 26200 points

Rafael,

now it is O.K.
C2000 ... is on top.
It is even in an alphabetical order.

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CCS/TMS320F28027: Methods for obtaining different frequencies of sine wave