CCS/TMS320F28379D: TMS320F28379D

Alexander Pasihov

Prodigy 230 points

Part Number: TMS320F28379D

Tool/software: Code Composer Studio

Hello,

My task needs to toggle GPIO pin fast a possible (limit is 50 nano sec), but now I measured toggle period as 156 nano.

My example activates CPU1 only : CSYSCLK 200Mhz

The GPIO toggle function is placed into RAM. Only GPIO63 (GPIOB group) is in use.

The following function runs in example (for measurement):

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#pragma CODE_SECTION(CalulateAnsMeasureNano, ".TI.ramfunc");

void CalulateAnsMeasureNano(void)
{
// Idle loop

for(;;)
{
GpioDataRegs.GPBDAT.bit.GPIO63 = 0;
GpioDataRegs.GPBDAT.bit.GPIO63 = 1;

}

/////////////////////////////////////////////////////////////////////////////////////

How to activate the GPIO pin switch faster ?

Thanks in advance,

AlexP

over 6 years ago

0 Vivek Singh over 6 years ago

TI__Guru** 116081 points

Hi Alex,

Two suggestions -

1) You should use SET and CLEAR register instead of DAT register.

2) Instead of writing particular bit (that is READ MODIFY WRITE operation), write full 32bit register (use .all).

That should bring the number down.

Regards,

Vivek Singh

0 Alexander Pasihov over 6 years ago in reply to Vivek Singh

Prodigy 230 points

Hi Vivek,

it's very helpful for me - I made 1)2) and now I have toggle period 78 nano instead 156,

But I need less of 50 nano....

May be GPIO63 is slow ? May any other pin will be faster ?

Thank you very much for your assistance ,

AlexP

0 Vivek Singh over 6 years ago in reply to Alexander Pasihov

TI__Guru** 116081 points

AlexP,

This is because of GPIO register access time. If you look at assembly, how many instruction you have for GPIO write?

Regards,

Vivek Singh

0 Alexander Pasihov over 6 years ago in reply to Vivek Singh

Prodigy 230 points

Hello Vivek,

The following fragment is derived from TMS320F28379D specification (documents SPRS880K –DECEMBER 2013–REVISED NOVEMBER 2018) :

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

5.9.6.1 GPIO - Output Timing

Table 5-23 shows the general-purpose output switching characteristics. Figure 5-12 shows the generalpurpose
output timing.
Table 5-23. General-Purpose Output Switching Characteristics
over recommended operating conditions (unless otherwise noted)

PARAMETER MIN MAX UNIT
tr(GPO) Rise time, GPIO switching low to high All GPIOs 8(1) ns
tf(GPO) Fall time, GPIO switching high to low All GPIOs 8(1) ns
tfGPO Toggling frequency, GPO pins 25 MHz

(1) Rise time and fall time vary with load. These values assume a 40-pF load.

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Is written that "toggling frequency, GPO pins = 25 MHz" - How I can I implement this (25 +/-) toggle in program?

Sincerely,

AlexP

0 Vivek Singh over 6 years ago in reply to Alexander Pasihov

TI__Guru** 116081 points

Hi Alex,

That number is from IO toggle capability but actual toggle frq will depend on GPIO access time and code execution. Can you post the snapshot of your assembly code.

Regards,

Vivek Singh