TMS320F280025: Changing the GPIO muxing due to faulty hardware

Benedikt Bromma

Part Number: TMS320F280025

Hello there,

I am a student working on a project with the tsm320f2800. I have created a hardware design and need two PWM signals (A&B are inverted) that are 180 degrees out of phase to switch 4 FETs. I am using the ePWM3 and ePWM4.
The default settings are these:

ePWM3_A -> GPIO4
ePWM3_B -> GPIO5

ePWM4_A -> GPIO6
ePWM4_B -> GPIO7

But on my board GPIO 4&6 is conecctetd as my first PWM signal and GPIO 5&7 as my second. Is it possible to change the muxing to get a high signal from ePWM3 and low signal from epwm4 at the same time and half a period later on the other side?

over 2 years ago

0 Nima Eskandari over 2 years ago

TI__Guru 51940 points

Are EPWM3 and EPWM4 running at the same frequency? TBPRDs are the same?

0 Benedikt Bromma over 2 years ago

Prodigy 10 points

Hello,

yes, EPWM3 and EPWM4 are running at the same frequency (1MHz).

0 Nima Eskandari over 2 years ago in reply to Benedikt Bromma

TI__Guru 51940 points

Okay then you have a chance. You can configure the EPWM3 and EPWM4 differently in SW.

For example dont use the PHSEN or TBPHS (PHSEN = 0, TBPHS= 0).

Instead embed the phase shift INTO THE CMPx event registers.

Nima

0 Benedikt Bromma over 2 years ago in reply to Nima Eskandari

Prodigy 10 points

So I had to check the Technical Reference Manual, so you mean linking the two ePWM modules together, with the EPWMXLINK (EPWMx Link Register)?

Would it not work to configure other GPIOs as ePWM signal:

void InitEPwm3Gpio(void)
{
GpioCtrlRegs.GPAMUX1.bit.GPIO4 = 1;
GpioCtrlRegs.GPAMUX1.bit.GPIO7 = 1;
}
void InitEPwm4Gpio(void)
{
GpioCtrlRegs.GPAMUX1.bit.GPIO5 = 1;
GpioCtrlRegs.GPAMUX1.bit.GPIO6 = 1;
}

or does this not work because they come from a different register? sorry I don't know much about this.

Benedikt

0 Nima Eskandari over 2 years ago in reply to Benedikt Bromma

TI__Guru 51940 points

Benedikt Bromma said:
void InitEPwm3Gpio(void)
{
GpioCtrlRegs.GPAMUX1.bit.GPIO4 = 1;
GpioCtrlRegs.GPAMUX1.bit.GPIO7 = 1;
}
void InitEPwm4Gpio(void)
{
GpioCtrlRegs.GPAMUX1.bit.GPIO5 = 1;
GpioCtrlRegs.GPAMUX1.bit.GPIO6 = 1;

These select MODE1. Whether MODE 1 is an EPWM mode or the another peripheral, you have to check the datasheet.

I dont think you need EPWMXLINK. Thats a different feature. You need to shift CMPx values with the phase shift value.

Nima

0 Benedikt Bromma over 2 years ago in reply to Nima Eskandari

Prodigy 10 points

Nima Eskandari said:
You need to shift CMPx values

Hi,

so i coudn't figure out, how to do that.

I'm now trying to create a phaseshift between signal A and B plus the phaseshift between the two ePWMs. I just don't know if this works out, because of the deadband. I have to ceck this on Dev Board and display the signals. But could this be another possibility?

Benedikt

0 Nima Eskandari over 2 years ago in reply to Benedikt Bromma

TI__Guru 51940 points

Yes so this is an example.

EPWM1 Period = 1000 (TBPRD)

CMPA = 300

EPWM2 Period = 1000 (TBPRD)

CMPA = 600

If you use CMPA to toggle the EPWM output, then the signals will have a 300 COUNT offset (phase shift).

0 Benedikt Bromma over 2 years ago in reply to Nima Eskandari

Prodigy 10 points

Thanks for that! That means I have to use the TB_COUNT_UP_DOWN (I have always only counted up), set one dutycycle = CMPA and the second CMPB = PRD - dutycycle and invert the output of this ePWM. Is that correct? But this has the disadvantage, that I need twice the frequency, but that's okay for the moment.

I also did some research on XBar, is it possible to build an ePWM-Xbar-architecture and re-route the inputs and outputs?

0 Nima Eskandari over 2 years ago in reply to Benedikt Bromma

TI__Guru 51940 points

Benedikt Bromma said:
I also did some research on XBar, is it possible to build an ePWM-Xbar-architecture and re-route the inputs and outputs?

Unfortunately, no EPWM XBAR is not used for that purpose!

-Nima

If you use the COUNT UP-DONW, you do have to change your PERIOD to be double to have the same frequency.

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TMS320F280025: Changing the GPIO muxing due to faulty hardware