what is cpu clock for piccolo f28069

Hello Pradeep,

I don't think I am fully understanding your question.  The F28069 is rated up to 90 MHz (see the device datasheet, SPRS698C).  Whether the user runs at 90 MHz or not is up to the user.  The internal oscillators on the F2806x are 10 MHz.  People use the PLL to crank this up to their operating speed (e.g., x18/2 gives 90 MHz).  You can also use an external crystal or oscillator as the clock source instead of the internal oscillator.  I'm not sure if that is what you are referring to with your mention of a 6 MHz frequency.

The ADC clock is specified up to 45 MHz.  There is a bit in the ADCCTL2 register that specifies if you want ADCCLK to be CPUCLK, or CPUCLK/2.  CPUCLK is, for example, the 90 MHz.  The ADCCLK doesn't affect your sampling rate unless you just put the ADC into a free-run setup where it is just converting as fast as possible.  This is not a typical mode of operation however.  Most people use a time to trigger the ADC at the desired sampling rate.  There is code with appnote SPRA958 (on TI web) that has the ADC triggering at 50 kHz from ePWM2.  The setup all depends on your CPUCLK, which for the appnote code is 90 MHz.

Regards,

David

Hi,

I'm also using the F28069 and I'm trying to sample one channel at 1 MHz. I've tried two different things: setting up the sample rate with a PWM (SysClk at 80MHz, PWM period of 80, ADCINT triggered after EOC)  and using a continuous sample mode (ADCINT triggers the SOC). I need this data to be saved in a buffer for future processing. 

I'm determining the sampling speed by putting a GPIO toggle in the ADCINT and looking at an oscilloscope. 

The PWM method seems to work well, and I get about 1 MHz, but with the continuous sampling mode, I get a very low frequency of about 200 kHz, and I have no idea why. Shouldn't it be faster than the PWM method? To my knowledge, the ADCCLK should be at 40MHz (I haven't divided it down).

Thanks,

Matthew 

Matthew,

You should definitely be able to get >1MSPS from a self-triggering scheme.  I think if you search around the forum, you should be able to find working code for this (F2803x and F2802x devices should have more-or-less compatible code for this).