8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

RE: 8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

ViktorVarjas — Fri, 28 Jul 2023 13:25:54 GMT

Hi,

In the meantime I found another solution that achieves 8Mhz (verified externally) and requires no additional lines in the prj.conf and in general is a simpler solution.

This is the code needed:

void startClock_8MHz(void)
{
	NRF_TIMER1->PRESCALER = 0; // 16MHz
    NRF_TIMER1->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Msk;
    NRF_TIMER1->CC[0] = 1;

    NRF_GPIOTE->CONFIG[0] = GPIOTE_CONFIG_MODE_Task | (2 << GPIOTE_CONFIG_PSEL_Pos) |
                            (GPIOTE_CONFIG_POLARITY_Toggle << GPIOTE_CONFIG_POLARITY_Pos);

    /*Connect TIMER event to GPIOTE out task*/
    NRF_PPI->CH[0].EEP = (uint32_t) &NRF_TIMER1->EVENTS_COMPARE[0];
    NRF_PPI->CH[0].TEP = (uint32_t) &NRF_GPIOTE->TASKS_OUT[0];
    NRF_PPI->CHENSET   = 1;

    /*Starts clock signal*/
    NRF_TIMER1->TASKS_START = 1;
}

To stop the clock:

NRF_TIMER1->TASKS_STOP = 1;

All the best,

Viktor

RE: 8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

Jared — Wed, 19 Jul 2023 14:09:19 GMT

Hi,

I tested the example and agree, I see that ticks has to minimum be 2 for it to be stable, making 4 MHz the lowest possible.

I'm sorry for the confusion,

regards

Jared

RE: 8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

ViktorVarjas — Tue, 18 Jul 2023 15:30:55 GMT

Hi!

If I use both at the same time it is not working, but when changing CONFIG_NRFX_TIMER0 to CONFIG_NRFX_TIMER1, it seems to work fine.

With the 16 Mhz base clock I can only generate 4Mhz clock signal max, when setting the "desired_ticks" to 4. It seems that desired_ticks = 1 is not possible or at least it didn't work for me (that would generate 8 Mhz)

Is there any option to modify the starting point project in a way to use a higher frequency (eg.: 32 MHz) base clock?

All the best,

Viktor

RE: 8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

Jared — Mon, 17 Jul 2023 10:47:04 GMT

Hi,

What error message do you get when you try to enable both of them?

regards

Jared

RE: 8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

ViktorVarjas — Mon, 17 Jul 2023 08:40:28 GMT

Hi!

Is there any way to do it without GPIOTE? The issue is that to use the solution you suggested the gpio module has to be disabled (CONFIG_GPIO=n) otherwise the 2 modules interfere with each other.

All the best,

Viktor

RE: 8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

Jared — Thu, 13 Jul 2023 07:59:57 GMT

Hi,

You can use this example as a starting point,

regards

Jared

RE: 8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

ViktorVarjas — Wed, 12 Jul 2023 14:51:05 GMT

Hi Jared,

Could you please provide an example on how to do it?

Thank you in advance,

Viktor

RE: 8.192 MHz clock signal on GPIO pin with nRF Connect SDK 2.3.0

Jared — Wed, 12 Jul 2023 10:43:33 GMT

Hi,

PWM supports up to about 5 MHz, so I think the best alternative would be to use a Timer + PPI + GPIOTE,

regards

Jared