TMDSCNCD28379D: Generating 450KHz PWM Sine Wave

Vishal D

Part Number: TMDSCNCD28379D
Other Parts Discussed in Thread: CONTROLSUITE, C2000WARE

Hello TI Team, In one of my product I want to generate 400KHz sine wave using ePWM module with at least 20 data points of carrier which will be modulated based on Sine table for 0 to 360 degree angle. Wanted to know if it is possible to do using C2000 series of microcontroller as the carrier frequency for 20 data points will be around 8 MHz? If it is feasible to do then can you please share any application note where such example is given ?

Thanks!

over 2 years ago

0 Ryan Ma over 2 years ago

TI__Mastermind 26916 points

Hi Vishal,

This post talks about generating sPWM using 28379D device.

Here are a few threads that may help you:

1. https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/779876/ccs-tms320f28379d-pulse-width-modulation---spwm

2. https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/532896/sine-wave-modulated-pwm

In addition to these we have controlSUITE that does have an example for this.

www.ti.com/.../CONTROLSUITE

Best,

Ryan Ma

0 Vishal D over 2 years ago in reply to Ryan Ma

Prodigy 70 points

Hello Ryan, Thank you for the suggestions. I'll go through the provided examples.

0 Vishal D over 2 years ago in reply to Ryan Ma

Prodigy 70 points

Hello Ryan, I tried creating sine look up table which will load the COMPA/COMPB registers of epwm at every interrupt of carrier frequency(8 MHz) however it appears that micro-controller gets stuck while updating registers in ISR.

With Timer in up mode and carrier frequency of 8 MHz (PWM frequency) the timer period register value come to 25 for 200MHz clock. Not sure if controller is able to process interrupts at such a faster rate and also process other application logic.

Can you please guide is there any better way to do it, may be using DMA or other module?

+1 Peter Luong1 over 2 years ago in reply to Vishal D

TI__Mastermind 18531 points

Hi Vishal,

How are you updating the CMPA/CMPB registers of the EPWM? If you are using DriverLib, you may experience greater latency in your ISR, to which I would recommend using register manipulation like below:

HWREGH(EPWM1_BASE+ EPWM_O_CMPA + 0x1U) = PWM1_CMPA_VAL;

Also note that the EPWM clock on F28379D runs at 100 MHz (there's a divider that divides SYSCLK/2). You can use HRPWM to achieve your desired 8 MHz toggling frequency.

An alternate method for generating a sine wave modulated PWM is to use the RAMPGEN library available within our digital power SDK. You can configure your fundamental frequency to generate a ramp signal which you can then pass into a sine function and generate the sine values dynamically.

You are working with high frequency values so I recommend making use of HRPWM for maximum resolution

Regards,

Peter

+1 Ryan Ma over 2 years ago in reply to Vishal D

TI__Mastermind 26916 points

Hi Vishal,

In addition to Peter's response:

Yes this is possible to do with DMA. Here is an e2e thread discussing the idea you're describing.

1. https://e2e.ti.com/support/wireless-connectivity/wi-fi-group/wifi/f/wi-fi-forum/696482/cc3200-pwm-signal-generate-by-dma-data-example-code-applying

Please refer to this, there is also C2000WARE example of using DMA found within our PWM examples

C:\ti\c2000\C2000Ware_<version>\driverlib\<device>\examples\epwm\epwm_ex_9_dma.c

0 Vishal D over 2 years ago in reply to Ryan Ma

Prodigy 70 points

Hello Ryan and Peter, Thank you for your response. I will try the suggested method to generate SPWM. I am using Driverlib to update PWM duty cycles which might be reason, so will shift to HW register manipulation.

For now you can close the thread, if any assistance is needed we will connect back.

Thanks,

Vishal

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TMDSCNCD28379D: Generating 450KHz PWM Sine Wave