QTMR resets all counters upon capture

[madisonchou]

In Kinetis FTM module, it has only one counter that serves multiple timer input or output.   In RT, the 4 counters in a QTMR are independent.   Is there a way to clear other 3 counters when the master (say counter0) is reset (i.e. reload) upon capture event?

The equivalent code for Kinetis FTM is here:

FTM0->CONTROLS[ 0 ].CnSC = FTM_CnSC_ELSA_MASK + FTM_CnSC_ICRST_MASK; // MSB:MSA=00=input capture; ELSB:ELSA=01=rising edge; CNT reset on edge
FTM0->CONTROLS[ 1 ].CnSC = FTM_CnSC_ELSA_MASK; // MSB:MSA=00=input capture; ELSB:ELSA=01=rising edge
FTM0->CONTROLS[ 2 ].CnSC = FTM_CnSC_ELSA_MASK; // MSB:MSA=00=input capture; ELSB:ELSA=01=rising edge

FTM0->SC = FTM_SC_CLKS( 1 ); // Enable FTM @ 40MHz BUS_CLK; PS=div1

The behavior of above code is...

• FTM0_CH0 rising edge is detected and counter value is latched into C0V.   The counter is reset to 0.
  • If the FTM0_CH0 input is a square wave, C0V measures its period.
• Subsequently when FTM0_CH1 rising edge comes up, counter value is latched into C1V.
  • C1V in effect is the period between the two rising edges.   In other words, C1V measures the delay from CH0 to CH1.
• FTM0_CH2 is the same as CH1.   Its capture, C2V, represents the delay from CH0 to CH2.

Thanks!! 

[madisonchou]

Hi Jeremy,

I would hope that you reflect my issue back to the team, first verify my finding, then when proving true, update RT family's Reference Manual.

Regards,

Jei

[madisonchou]

Hi Jeremy,

Thanks for prompt reply.   But the reset counters applies only to Compare event.   What I am looking for is the Capture event.   I haven't done exhausted testing yet.   But thus far, it doesn't work for Capture event.

Any other thoughts?

Jei

[jeremyzhou]

Hi Jei Chou,

Thank you for your reply.
I'm afraid that QTMR doesn't support to initialize all four counter/timer upon the capture event happens.
Hope this is clear.

Have a great day,
TIC

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[madisonchou]

Jeremy,

After experimenting some more, the counter reset by Master seems to work!

Attached is the changes to example project of iled_blinky.   I feed external 5KHz square waves to inputs of QTMR3.   Each input has different delay (leading or lagging) to Master.

• TMR3_TIMER0 == GPIO_AD_B1_00 == RT1060 EVK J24-10 (Master)
• TMR3_TIMER1 == GPIO_AD_B1_01 == RT1060 EVK J24-9, lag by 5uS
• TMR3_TIMER2 == GPIO_AD_B1_02 == RT1060 EVK J22-7, lag by 10uS
• TMR3_TIMER3 == GPIO_AD_B1_03 == RT1060 EVK J22-8, lead by 5uS

The debug output shows reasonable captures:

Enter any key => 1
15180, 14799, 14421, 378

[madisonchou]

Here is the attachment.

[jeremyzhou]

Hi Jei Chou,

Thanks for the sharing:smileyhappy:.
Have a great day,
TIC

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[jeremyzhou]

Hi Jei Chou,

Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
Q1)  Is there a way to clear other 3 counters when the master (say counter0) is reset (i.e. reload) upon capture event?
-- It's able to clear other 3 counters when the master encounters a compare event if enabling the COINIT feature.

Have a great day,
TIC

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