F28027 LaunchPad, PWM not giving a constant output frequency

Pankaj Kadam

Intellectual 480 points

Other Parts Discussed in Thread: TMS320F28027

Hi all,

I am using the TMS320F28027 Piccolo LaunchPad on CCS5.

I am generating a 10Khz PWM, by loading

EPwm3Regs.TBCTL.bit.HSPCLKDIV = 0x03; //HS CLK prescale = 6

EPwm4Regs.TBPRD = 1000; // (60Mhz/6 *10Khz)

but the output frequency keeps varying between 10Khz, 9Khz and 6Khz.

I tried TI website but didn't get detailed document of the PWM module for the Launchpad, they do have documents on HPWM and Enhanced PWM but I wanted more detail on initializing Peripheral clock which triggers the PWM modules.

In the DSP2802X_SysCtrl.C I found it has two Internal Oscillator, IntOsc1Sel and IntOsc2Sel, I tried to use either of them but still the output frequency kept changing...

Thanks in advance.

Pankaj

over 12 years ago

0 BrandonAzbell over 12 years ago

TI__Guru 64920 points

Pankaj Kadam said:

I tried TI website but didn't get detailed document of the PWM module for the Launchpad, they do have documents on HPWM and Enhanced PWM but I wanted more detail on initializing Peripheral clock which triggers the PWM modules.

Detailed information of the ePWM module would be found on the TMS320F28027 Product Folder in the TMS320x2802x, 2803x Piccolo Enhanced Pulse Width Modulator (ePWM) Module UG (Rev. E).

The Launchpad is an evaluation platform that instantiates a particular device, in this case the TMS320F28027. Documentation on peripherals associated with the device will be found on the device product folder.

0 Pankaj Kadam over 12 years ago in reply to BrandonAzbell

Intellectual 480 points

Hi Brandon,

I solved the problem, earlier I was giving float value to the EPwm1Regs.CMPA.half.CMPA register for my variable duty cycle, after giving it only integer values, the output frequency was improved. I also enabled the shadow registers.

Thank for pointing me to the right direction.

Best Regards,

Pankaj

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F28027 LaunchPad, PWM not giving a constant output frequency