CC2340R5: Pulse counter for LMT01

Sam Lin46

Part Number: CC2340R5
Other Parts Discussed in Thread: LMT01,

Tool/software:

I used pulse counter for LMT01 on CC2640R2, now I want to use pulse counter for LMT01 on CC2340R5 however I cannot find suitable API.

Does CC2340R5 supports pulse counter for integrating LMT01 ?

over 1 year ago

0 Arthur R☑️ over 1 year ago

TI__Mastermind 27887 points

Hi Sam,

I believe that after setting up your timer to count on external events:

you can use the following API: https://dev.ti.com/tirex/explore/content/simplelink_lowpower_f3_sdk_9_10_00_83/docs/drivers/doxygen/html/_l_g_p_timer_l_p_f3_8h.html#a5eaa994c40e4b8ed2946c607157f92dc

Regards,

Arthur

0 Sam Lin46 over 1 year ago in reply to Arthur R☑️

Intellectual 430 points

Hi Arthur,

Is there a code snip or example for reference ?

I didn't find edge pulse counting mode in doc like CC2640R2.

e.g.

dev.ti.com/.../_l_g_p_timer_l_p_f3_8h.html

Which mode should I use ?

0 Ryan Brown1 over 1 year ago in reply to Sam Lin46

TI__Guru**** 223167 points

Hi Sam,

You will use the LGPTimerLPF3_CH_PULSE_WIDTH_MEASURE channel action and LGPTimerLPF3_CTL_MODE_UP_ONCE or LGPTimerLPF3_CTL_MODE_UP_PER as function argument for LGPTimerLPF3_start(). Unfortunately there are no out-of-box examples from TI provided for this feature, you can reference these two relevant E2E threads. Depending on your project's requirements you may also be able to achieve the desired functionality with a GPIO interrupt pin.

Regards,
Ryan

0 Sam Lin46 over 1 year ago in reply to Ryan Brown1

Intellectual 430 points

Hi Ryan,

I don't get the point of using LGPTimerLPF3_CH_PULSE_WIDTH_MEASURE to count number of pulses.

It seems to interrupt CPU on pulse edge for measuring pulse width or period by ticks between 2 edges.

For pulse counting it's nothing different to increment count in GPIO isr.

However LMT01 pulse freq is 80KHz which is over GPIO isr capability.

It's a simple function by default available in CC2640R2 however I cannot find in CC2340.

And I don't think LGPTimerLPF3_CH_PULSE_WIDTH_MEASURE is relevent to this use case.

Any help ?

0 Ryan Brown1 over 1 year ago in reply to Sam Lin46

TI__Guru**** 223167 points

You are correct and I apologize for the confusion, the CC13XX / CC26XX has a GPT hardware peripheral with specific edge-count mode whereas the CC23XX LGPT hardware peripheral offers "set on capture" or "pulse width measurement" continuous capture modes.

Sam Lin46 said:
However LMT01 pulse freq is 80KHz which is over GPIO isr capability.

How did you figure this out? The CC2340R5 main clock is 48 MHz which should leave plenty of processing room to count pulses. UART RX bit banging implementations have successfully run at 115200 baud with this device so it should be capable of handling 88 kHz.

Regards,
Ryan

0 Sam Lin46 over 1 year ago in reply to Ryan Brown1

Intellectual 430 points

Hi Ryan,

are you saying GPIO interrupt handler in FreeRTOS can handle 88kHz frequency ?

where can I find doc about the maximum freq that GPIO handler can handle ?

0 Ryan Brown1 over 1 year ago in reply to Sam Lin46

TI__Guru**** 223167 points

I ran a test where I am sending a 200 kHz pulse to the CC2340R5 and measuring the number of pulses accurately every second using the GPIO ISR in a FreeRTOS environment. Of course the MCU is rather loaded during this time but with a slower frequency and selecting when to measure the LMT01 (i.e. disabling the GPIO when you do not need a measurement) is should be possible to achieve this within your application.

Regards,
Ryan

0 Sam Lin46 over 1 year ago in reply to Ryan Brown1

Intellectual 430 points

Hi Ryan,

Thank you I'll take GPIO isr as backup plan.

I still want to use LGPT for pulse counter if possible.

basic idea is GPIO pin as timer input (e.g. clock) and get count.

Do you think that's feasible with LGPT ?

0 Ryan Brown1 over 1 year ago in reply to Sam Lin46

TI__Guru**** 223167 points

Hi Sam,

I will ask around internally and get back with you on options.

Regards,
Ryan

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CC2340R5: Pulse counter for LMT01