TMS570LS1224: eCAP: Higher frequency Square wave Capture Limitation

Sonal Prasad

Part Number: TMS570LS1224
Other Parts Discussed in Thread: HALCOGEN

Hello.

I have configured the eCAP1 register via halcogen. When i try to feed the square wave of 50% duty cycle and 1 Khz frequency i dont see any updates on ecapREG1.CAP1-CAP4. but when i feed the input with 500hz i can see the updates on the timing registers(cap1-cap4). i tried with prescaler and it updates max to 800 hz.

Question is is there a limitation for higher frequency and duty cycle on ecap or am i missing any configuration?

My halcogen configuration for eCAP1:

i am trying to use the below mentioned configuration in manual for TMS570.

any pointers would be helpful.

Regards,

Sonal

over 3 years ago

0 QJ Wang over 3 years ago

TI__Guru**** 196756 points

Hi Sonal,

To measure period AND duty cycle, can you try this settings? Your setting is not able to measure duty cycle.

Why do you RESET ecap1/2/3/4 counters after each capture? All the ECAP counters are cleared after each rising edge.

0 Sonal Prasad over 3 years ago in reply to QJ Wang

Prodigy 10 points

Hello QJ,

So i had reset all of them as per the example in pdf.

I set up the Halcogen as per your advice. I still have the same issue. My timer registers (cap1-cap5) do not get updated when i set my pwm frequency from function generator to 1 khz. But it does get updated till 900 Hz.

so i am attaching a register snapshot.

so question is am i missing some configuration?

Regards,

Sonal

0 QJ Wang over 3 years ago in reply to Sonal Prasad

TI__Guru**** 196756 points

Sonal Prasad said:
My timer registers (cap1-cap5) do not get updated

CAP4 and CAP5 are not used in this setting. The CAP1, CAP2, and CAP3 should be updated at edge event1, edge event 2, and the edge event 3.

The ECAP doesn't give period and duty cycle. You need to calculate them using the values in CAP1 (rising edge), CAP2 (falling edge), and CAP3 (rising edge). How do you get the period of 900Hz? Your snapshot shows that CAP1/2/3 has the same value.

0 QJ Wang over 3 years ago in reply to QJ Wang

TI__Guru**** 196756 points

There is something wrong with your configuration. Please post your HALCOGEN files (*.hcg and *.dil).

Please double check your ECAP settings:

0 Sonal Prasad over 3 years ago in reply to QJ Wang

Prodigy 10 points

Hello Qj,

So i know that i wont get the period and duty by deault. so i am calculating that via following:

cap_val3 = (float32)ecapGetCAP3(ecap);
cap_val2 = (float32)ecapGetCAP2(ecap);
cap_val1 = (float32)ecapGetCAP1(ecap);

eCAPperiod = cap_val3-cap_val1;
eCAPOntime = cap_val2 - cap_val1;

if(eCAPperiod >=1)

{

freq = clkfreq/eCAPperiod;

duty = eCAPOntime/eCAPperoid;

}

Hope the above code makes sense;

i am also attaching the *cfg and *.dil

As per question why registers are not updating (My timer registers (cap1-cap5) do not get updated): Even i had doubt why update in register stops when i switch the pwm frequency to 900hz from function generator that i feed in.

Regards,
Sonal