CCS/AM3358: 90MHz PWM frequency

Maique Garcia

Part Number: AM3358

Tool/software: Code Composer Studio

Hi. I am trying to work with ePWM on Sitara AM3358 on PRU0 program. It is working but i cant reach the desired frequency of 1920 Hz on PWM output.

One way to get this frequency (or more near to this frequency) is changing the SYSCLKOUT clock for my PWM module. And looking to the table 15.41 on AM335x datasheet October 20011 (attached in this post), i saw a possible configuration of 90 MHz of PWM frequency. My question is:

Is possible to get this 90MHz (and other system frequencies) to feed the PWM module? How?
I think the key is TBCLK preescales. But could i get 90 MHz withou use high resolution mode?

Thanks:

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Hi,

The PWMSS functional clock is the CORE_CLKOUTM4/2 clock. It's fixed to 100MHz. If you try to change it this could cause unreliable functioning of the whole system. You should note that descriptions of the peripheral modules in the TRM are generic, and some settings may not apply to the particular device.

0 Biser Gatchev-XID over 7 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Besides, I don't see what's the problem here. With 100MHz functional clock you have a 10ns resolution. If you set TBPRD=52082 then you will have a period of 52083 * 10ns = 520.83ns, which is 1920.012Hz. This is an error of less than 0.001%.

0 Maique Garcia over 7 years ago in reply to Biser Gatchev-XID

Prodigy 225 points

Thank you Biser. Looking the table I thought that could be an problem with the sysclock on PWM..

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CCS/AM3358: 90MHz PWM frequency