Toggle frequency on GPIO TMS320F28335

Javier Torres

Other Parts Discussed in Thread: TMS320F28335, CONTROLSUITE

Hi,

I've configured SYSCLKOUT of TMS320F28335 at 150MHz. I've tried to toggle a GPIO but, to my surprise, it only toggles at 4MHz (4,17 MHz i've measured)

I know that SYSCLKOUT is correctly configured because i have interruptions and PWMs running at the correct frequency.

Why is there so much difference between SYSCLKOUT frequency and the toggling frequency?

Thank you.

over 11 years ago

0 Igor Gorbachev over 11 years ago

Guru 20525 points

Hi, Javier.

In general according SPRS439M there is the following switching limit for GPIO:

But also it is important what is mechanism you use for toggling (timer's ISR or something else).

Regards,

Igor

0 Javier Torres over 11 years ago in reply to Igor Gorbachev

Prodigy 50 points

Hi Igor, I'm using the toggle register (GPxTOGGLE) to toggle a GPIO that is configured as an output. Acording to the dinamic specifications that you show me, i should be able to switch the pin up to 25MHz, but that's not the case. What am i missing? Regards.

0 Igor Gorbachev over 11 years ago in reply to Javier Torres

Guru 20525 points

Javier,

Javier Torres said:

I'm using the toggle register (GPxTOGGLE) to toggle a GPIO that is configured as an output.

It is clear, but what is a code realisation? Do you implement toggling within some simple ifinite loop?

Regards,

Igor

0 Javier Torres over 11 years ago in reply to Igor Gorbachev

Prodigy 50 points

Yes, the toggling is implemented within an infinite loop. It is the only instruction within the loop right now, the rest of code is execute within an interruption that interrupts with 60kHz frequency. Is in between two interruptions when the pin toggles with a 4MHz frequency. Regards.

0 Igor Gorbachev over 11 years ago in reply to Javier Torres

Guru 20525 points

Javier,

I think the best way for checking is to create code with one simple loop inside "main( )" without any additional ISR.

Regards,

Igor

0 Javier Torres over 11 years ago in reply to Igor Gorbachev

Prodigy 50 points

Thank you Igor for your suggestion. I've just tested as you proposed and is still toggling at the same frequency.

0 Igor Gorbachev over 11 years ago in reply to Javier Torres

Guru 20525 points

It is strange. Just in case check how you specify the clock rate of the CPU (SYSCLKOUT). For example, refer please to this file:

ti\controlSUITE\device_support\f2833x\v133\DSP2833x_common\include\DSP2833x_Examples.h

Regards,

Igor

0 Igor Gorbachev over 11 years ago in reply to Igor Gorbachev

Guru 20525 points

Hi, Javier.

Also, could you please clarify, what project's configuration do you use: loading from FLASH or RAM?

Regards,

Igor

0 Javier Torres over 11 years ago in reply to Igor Gorbachev

Prodigy 50 points

Thank you for pointing that out, Igor. It has really help me. I'm running my program from flash. After reading your comment, i've tried to modifwait states executed and write accesses in the flash memory and... voilà, it affects the toggling frequency of the GPIOs and the overall performance of my program. The toggling frequency has only increase to 5,7 MHz and is still far from the theoric maximum, but this boost allows me to execute all he instructions that i need within an interruption (which was my real problem), so i'm really grateful. Best regards, Javier Torres

0 Igor Gorbachev over 11 years ago in reply to Javier Torres

Guru 20525 points

Javier,

1) in general the best way of incrising performance is to copy time-critical code sections into RAM from FLASH. You can refer to this AR 4062.TI_Running_from_Flash_spra958l.pdf.

2) would you like to repeat experiment with only toggling GPIO for RAM configuration of project? It would be interesting.

Regards,

Igor

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Toggle frequency on GPIO TMS320F28335