TMS320F28377D: TMS320F28377D

ok thank you for your early response iam using epwm as my trigger, EPwm3Regs.TBPRD = 0x66; and  EPwm3Regs.CMPA.bit.CMPA = 0x33;

can you provide me how to calculate sampling rate based on these two values.

Thank you for your early response ,and it work well for me.

double frequency or half it for reducing sampling rate?

Thank you so much.let me try and i will update .

in our present code the register values are given below and i tried doubling value also but still no change in sampling rate.

i need a sampling rate of 512 KB/Second

Present values

DEVICE       :TMS320F28377D

HSPCLKDIV = 0

TBPRD     = 0x66

CMPA      = 0x33

ACQPS     = 14

TRIGSEL   = 9

ADCCTL2.bit.PRESCALE = 6;

AdcbRegs.ADCCTL2.bit.RESOLUTION = 1;

 I already tried values given below 

HSPCLKDIV = 0

TBPRD     = 0x190

CMPA      = 0xC8

ACQPS     = 14

TRIGSEL   = 9

ADCCTL2.bit.PRESCALE = 6;

AdcbRegs.ADCCTL2.bit.RESOLUTION = 1;

But we are still getting sampling rate of 1 MB/seconds with above values.is there any other register needs to be changed?

Please let me know the details.

This looks pretty much fine. Just the values to reduce the frequency to half should be double of 0x66 and 0x33, i.e. 0xCC and 0x66. But anyways updating to the values you mentioned also should change the frequency.

How are you checking the frequency that you're mentioning? Also, can you check whether the EPWM frequency is getting updated according the set values?

HSPCLKDIV= 0,as per reference manual, sysclock ie 200M in my case will be fed to pwm, i hope its correct. Or is there any other multiplier or divider?ok let me check pwm frequency? Can i get pwm on any pinout? As i am feeding same pwm to adc

Can you refer to the ADC SOC with EPWM trigger example given along with C2000Ware? 

Ya i got the 500kB sampling rate now my new issue is need to sample 3 adc input, adc a, b, c. Iam using same configuration mention above but i want to get 1mb sampling rate for other two inputs, as iam using TBPRD value for 500KB ie 400.even iam using differe pwm3,9,1 iam getting 500 KB other channels too, i tried using one channel trigger with CMPB its not working. 

Or the direct question is whats best method to simultaneously sample adc a b c with different sampling rate.

Hi my new doubt is iam initialising 3 ADC same time b4 while one loop. So how will get different sampling rate as TBPRDA register is same? I need 2 Adc running at 1MB and 1 adc 512KB. How this can be achived also all adc should run parellel?

Hi Diji,

This requirement is demonstrated in the example adc_ex11_multiple_soc_epwm available with the C2000Ware_3_04 version.

The example demonstrates two ADCs operating in parallel at different frequencies. Request you to refer the example. It is not available with the versions prior to 3_04. Request you to check <C2000Ware_3_04_00_00\driverlib\f2837xd\examples\cpu1\adc>

Thanks,

Aditya

Ok thank you i solved this issue, issue was pwm ownership, i havnt set it for new pwm.

• But i have another  question in my cpu1 pressure sensor is sampled by adc D, how can i increase accuracy. If i increase s/h time wether accuracy increase?
• Or actually 2040 base line value and it should go increasing order till 2048 but its coming like 2040,2042,2040 again its wrong. So how can increase accuracy of my pressures  reading is there any h/w avg

Diji,

You can use the 16 bit feature of ADC for a higher resolution. As far as the accuracy is concerned, please refer to the device datasheet which contains the minumum and maximum error for the ADC module.

The output will be range bound but not exact.

Thanks,

Aditya

if my pwm is 100 K what should be aqusition time adc d samples for input.ACQPS VALUE

ok thank you

whether higher acquision window for example 200 ns improve accuracy?

Higher acquistion means you are giving longer time to charge the sampling capacitor. It'll help you gain some % in terms of accuracy but that won't be a big difference.

Aditya