nRF52 TIMER PPI GPIOTE dropouts/pauses issue

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

Sigurd — Thu, 21 Oct 2021 15:34:10 GMT

Hi,

You could try to simply use nrfx_timer_compare(), and see if that helps with the pauses:

void fm_set_duty(uint32_t period)
{

nrfx_timer_compare(&timer_inst_freq,
NRF_TIMER_CC_CHANNEL0,
period,
false);
}

#include <stdbool.h>
#include <stdint.h>
#include "nrf.h"
#include "nrf_drv_timer.h"
#include "nrf_drv_ppi.h"
#include "nrf_drv_gpiote.h"
#include "nrf_gpiote.h"
#include "nrf_gpio.h"
#include "app_error.h"
//#include "nrf_pwr_mgmt.h"
//#include "tone_array.h"

#define GPIO_FREQ_OUT 4
static const nrf_drv_timer_t timer_inst_t5ms = NRF_DRV_TIMER_INSTANCE(1); //!don't use TIMER0 with softdevice
static const nrf_drv_timer_t timer_inst_freq = NRF_DRV_TIMER_INSTANCE(3); //!don't use TIMER0 with softdevice
static nrf_ppi_channel_t     m_ppi_channel;
uint16_t tone_member = 1;
uint32_t timer_5ms_counter = 0;

#define TONE_TABLE_MEMBERS 1024 
const uint32_t tone_array[1024] = {
6400, 6398, 6395, 6393, 6390, 6388, 6385, 6383, 6380, 6378, 6375, 6373, 6370, 6368, 6365, 6363,
6360, 6358, 6356, 6353, 6351, 6348, 6346, 6343, 6341, 6338, 6336, 6333, 6331, 6329, 6326, 6324,
6321, 6319, 6316, 6314, 6311, 6309, 6307, 6304, 6302, 6299, 6297, 6295, 6292, 6290, 6287, 6285,
6282, 6280, 6278, 6275, 6273, 6270, 6268, 6266, 6263, 6261, 6258, 6256, 6254, 6251, 6249, 6247,
6244, 6242, 6239, 6237, 6235, 6232, 6230, 6228, 6225, 6223, 6220, 6218, 6216, 6213, 6211, 6209,
6206, 6204, 6202, 6199, 6197, 6195, 6192, 6190, 6188, 6185, 6183, 6181, 6178, 6176, 6174, 6171,
6169, 6167, 6164, 6162, 6160, 6157, 6155, 6153, 6150, 6148, 6146, 6143, 6141, 6139, 6137, 6134,
6132, 6130, 6127, 6125, 6123, 6121, 6118, 6116, 6114, 6111, 6109, 6107, 6105, 6102, 6100, 6098,
6095, 6093, 6091, 6089, 6086, 6084, 6082, 6080, 6077, 6075, 6073, 6071, 6068, 6066, 6064, 6062,
6059, 6057, 6055, 6053, 6050, 6048, 6046, 6044, 6042, 6039, 6037, 6035, 6033, 6030, 6028, 6026,
6024, 6022, 6019, 6017, 6015, 6013, 6011, 6008, 6006, 6004, 6002, 6000, 5997, 5995, 5993, 5991,
5989, 5986, 5984, 5982, 5980, 5978, 5975, 5973, 5971, 5969, 5967, 5965, 5962, 5960, 5958, 5956,
5954, 5952, 5949, 5947, 5945, 5943, 5941, 5939, 5936, 5934, 5932, 5930, 5928, 5926, 5924, 5921,
5919, 5917, 5915, 5913, 5911, 5909, 5907, 5904, 5902, 5900, 5898, 5896, 5894, 5892, 5890, 5887,
5885, 5883, 5881, 5879, 5877, 5875, 5873, 5871, 5868, 5866, 5864, 5862, 5860, 5858, 5856, 5854,
5852, 5850, 5848, 5845, 5843, 5841, 5839, 5837, 5835, 5833, 5831, 5829, 5827, 5825, 5823, 5820,
5818, 5816, 5814, 5812, 5810, 5808, 5806, 5804, 5802, 5800, 5798, 5796, 5794, 5792, 5790, 5788,
5786, 5784, 5781, 5779, 5777, 5775, 5773, 5771, 5769, 5767, 5765, 5763, 5761, 5759, 5757, 5755,
5753, 5751, 5749, 5747, 5745, 5743, 5741, 5739, 5737, 5735, 5733, 5731, 5729, 5727, 5725, 5723,
5721, 5719, 5717, 5715, 5713, 5711, 5709, 5707, 5705, 5703, 5701, 5699, 5697, 5695, 5693, 5691,
5689, 5687, 5685, 5683, 5681, 5679, 5677, 5675, 5673, 5671, 5669, 5667, 5666, 5664, 5662, 5660,
5658, 5656, 5654, 5652, 5650, 5648, 5646, 5644, 5642, 5640, 5638, 5636, 5634, 5632, 5630, 5629,
5627, 5625, 5623, 5621, 5619, 5617, 5615, 5613, 5611, 5609, 5607, 5605, 5604, 5602, 5600, 5598,
5596, 5594, 5592, 5590, 5588, 5586, 5584, 5583, 5581, 5579, 5577, 5575, 5573, 5571, 5569, 5567,
5565, 5564, 5562, 5560, 5558, 5556, 5554, 5552, 5550, 5549, 5547, 5545, 5543, 5541, 5539, 5537,
5535, 5534, 5532, 5530, 5528, 5526, 5524, 5522, 5520, 5519, 5517, 5515, 5513, 5511, 5509, 5507,
5506, 5504, 5502, 5500, 5498, 5496, 5495, 5493, 5491, 5489, 5487, 5485, 5484, 5482, 5480, 5478,
5476, 5474, 5473, 5471, 5469, 5467, 5465, 5463, 5462, 5460, 5458, 5456, 5454, 5452, 5451, 5449,
5447, 5445, 5443, 5442, 5440, 5438, 5436, 5434, 5433, 5431, 5429, 5427, 5425, 5424, 5422, 5420,
5418, 5416, 5415, 5413, 5411, 5409, 5408, 5406, 5404, 5402, 5400, 5399, 5397, 5395, 5393, 5391,
5390, 5388, 5386, 5384, 5383, 5381, 5379, 5377, 5376, 5374, 5372, 5370, 5369, 5367, 5365, 5363,
5362, 5360, 5358, 5356, 5354, 5353, 5351, 5349, 5348, 5346, 5344, 5342, 5341, 5339, 5337, 5335,
5334, 5332, 5330, 5328, 5327, 5325, 5323, 5321, 5320, 5318, 5316, 5315, 5313, 5311, 5309, 5308,
5306, 5304, 5302, 5301, 5299, 5297, 5296, 5294, 5292, 5290, 5289, 5287, 5285, 5284, 5282, 5280,
5278, 5277, 5275, 5273, 5272, 5270, 5268, 5267, 5265, 5263, 5262, 5260, 5258, 5256, 5255, 5253,
5251, 5250, 5248, 5246, 5245, 5243, 5241, 5240, 5238, 5236, 5235, 5233, 5231, 5230, 5228, 5226,
5225, 5223, 5221, 5220, 5218, 5216, 5215, 5213, 5211, 5210, 5208, 5206, 5205, 5203, 5201, 5200,
5198, 5196, 5195, 5193, 5191, 5190, 5188, 5186, 5185, 5183, 5181, 5180, 5178, 5177, 5175, 5173,
5172, 5170, 5168, 5167, 5165, 5163, 5162, 5160, 5159, 5157, 5155, 5154, 5152, 5150, 5149, 5147,
5146, 5144, 5142, 5141, 5139, 5138, 5136, 5134, 5133, 5131, 5129, 5128, 5126, 5125, 5123, 5121,
5120, 5118, 5117, 5115, 5113, 5112, 5110, 5109, 5107, 5105, 5104, 5102, 5101, 5099, 5098, 5096,
5094, 5093, 5091, 5090, 5088, 5086, 5085, 5083, 5082, 5080, 5079, 5077, 5075, 5074, 5072, 5071,
5069, 5067, 5066, 5064, 5063, 5061, 5060, 5058, 5057, 5055, 5053, 5052, 5050, 5049, 5047, 5046,
5044, 5042, 5041, 5039, 5038, 5036, 5035, 5033, 5032, 5030, 5029, 5027, 5025, 5024, 5022, 5021,
5019, 5018, 5016, 5015, 5013, 5012, 5010, 5009, 5007, 5005, 5004, 5002, 5001, 4999, 4998, 4996,
4995, 4993, 4992, 4990, 4989, 4987, 4986, 4984, 4983, 4981, 4980, 4978, 4977, 4975, 4973, 4972,
4970, 4969, 4967, 4966, 4964, 4963, 4961, 4960, 4958, 4957, 4955, 4954, 4952, 4951, 4949, 4948,
4946, 4945, 4943, 4942, 4940, 4939, 4937, 4936, 4934, 4933, 4931, 4930, 4929, 4927, 4926, 4924,
4923, 4921, 4920, 4918, 4917, 4915, 4914, 4912, 4911, 4909, 4908, 4906, 4905, 4903, 4902, 4900,
4899, 4898, 4896, 4895, 4893, 4892, 4890, 4889, 4887, 4886, 4884, 4883, 4881, 4880, 4879, 4877,
4876, 4874, 4873, 4871, 4870, 4868, 4867, 4865, 4864, 4863, 4861, 4860, 4858, 4857, 4855, 4854,
4852, 4851, 4850, 4848, 4847, 4845, 4844, 4842, 4841, 4840, 4838, 4837, 4835, 4834, 4832, 4831,
4830, 4828, 4827, 4825, 4824, 4822, 4821, 4820, 4818, 4817, 4815, 4814, 4812, 4811, 4810, 4808,
4807, 4805, 4804, 4803, 4801, 4800, 4798, 4797, 4796, 4794, 4793, 4791, 4790, 4789, 4787, 4786,
4784, 4783, 4782, 4780, 4779, 4777, 4776, 4775, 4773, 4772, 4770, 4769, 4768, 4766, 4765, 4763,
4762, 4761, 4759, 4758, 4757, 4755, 4754, 4752, 4751, 4750, 4748, 4747, 4745, 4744, 4743, 4741,
4740, 4739, 4737, 4736, 4734, 4733, 4732, 4730, 4729, 4728, 4726, 4725, 4724, 4722, 4721, 4719,
4718, 4717, 4715, 4714, 4713, 4711, 4710, 4709, 4707, 4706, 4705, 4703, 4702, 4700, 4699, 4698,
4696, 4695, 4694, 4692, 4691, 4690, 4688, 4687, 4686, 4684, 4683, 4682, 4680, 4679, 4678, 4676,
4675, 4674, 4672, 4671, 4670, 4668, 4667, 4666, 4664, 4663, 4662, 4660, 4659, 4658, 4656, 4655,
4654, 4652, 4651, 4650, 4648, 4647, 4646, 4644, 4643, 4642, 4640, 4639, 4638, 4636, 4635, 4634,
4633, 4631, 4630, 4629, 4627, 4626, 4625, 4623, 4622, 4621, 4619, 4618, 4617, 4616, 4614, 4613,
4612, 4610, 4609, 4608, 4606, 4605, 4604, 4603, 4601, 4600, 4599, 4597, 4596, 4595, 4594, 4592,
4591, 4590, 4588, 4587, 4586, 4584, 4583, 4582, 4581, 4579, 4578, 4577, 4576, 4574, 4573, 4572
};


void fm_set_duty(uint32_t period)
{

  nrfx_timer_compare(&timer_inst_freq,
                     NRF_TIMER_CC_CHANNEL0,
                     period,
                    false);
}


/**
 * @brief Handler for timer events.
 */
void t5ms_timer_event_handler(nrf_timer_event_t event_type, void *p_context)
{
    switch (event_type)
    {
        case NRF_TIMER_EVENT_COMPARE0:
            nrf_gpio_pin_toggle(3);
            fm_set_duty(tone_array[tone_member]);
            //**********tone_member table go up
            if (tone_member < (TONE_TABLE_MEMBERS-1))
            {
                tone_member++;
            }
            else if (tone_member >= (TONE_TABLE_MEMBERS-1))
            {
                tone_member = 0;
                // nrf_drv_timer_disable(&timer_inst_t5ms);
                // nrf_drv_timer_disable(&timer_inst_freq);
                // nrf_drv_ppi_channel_disable(m_ppi_channel);
                // nrf_drv_gpiote_out_task_disable(GPIO_FREQ_OUT);
            }
            //**********tone table go up

            //************30 sec ramp from tone table******
            if (timer_5ms_counter >= 6000)
            {
                nrf_drv_timer_disable(&timer_inst_t5ms);
                nrf_drv_timer_disable(&timer_inst_freq);
                nrf_drv_ppi_channel_disable(m_ppi_channel);
                nrf_drv_gpiote_out_task_disable(GPIO_FREQ_OUT);
            }
            timer_5ms_counter++;
            break;
    }
}


void freq_timer_event_handler(nrf_timer_event_t event_type, void *p_context)
{
}

/**
 * @brief Function for main application entry.
 */
int main(void)
{
    uint32_t time_ticks;
    uint32_t err_code = NRF_SUCCESS;

    err_code = nrf_drv_ppi_init();
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_gpiote_init();
    APP_ERROR_CHECK(err_code);

    //>>>GPIOTE init
    nrf_drv_gpiote_out_config_t config = GPIOTE_CONFIG_OUT_TASK_TOGGLE(false);

    err_code = nrf_drv_gpiote_out_init(GPIO_FREQ_OUT, &config);
    APP_ERROR_CHECK(err_code);
    //<<<GPIOTE init

    ////>>>TIMER init
    nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
    timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_16;

    err_code = nrf_drv_timer_init(&timer_inst_freq, &timer_cfg, freq_timer_event_handler);
    APP_ERROR_CHECK(err_code);

    //nrf_drv_timer_extended_compare(&timer_inst_freq,
    //                               NRF_TIMER_CC_CHANNEL0,
    //                               tone_array[0],
    //                               NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
    //                               false);
   // fm_set_duty(tone_array[0]); // MOVED
    ////<<<<TIMER init

    //>>>PPI init
    err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
    APP_ERROR_CHECK(err_code);

    uint32_t compare_evt_addr;
    uint32_t gpiote_task_addr;
    compare_evt_addr = nrf_drv_timer_event_address_get(&timer_inst_freq, NRF_TIMER_EVENT_COMPARE0);
    gpiote_task_addr = nrf_drv_gpiote_out_task_addr_get(GPIO_FREQ_OUT);

    err_code = nrf_drv_ppi_channel_assign(m_ppi_channel, compare_evt_addr, gpiote_task_addr);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);
    APP_ERROR_CHECK(err_code);

    nrf_drv_gpiote_out_task_enable(GPIO_FREQ_OUT);
    //<<<PPI init

    ////>>>TIMER init
    timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_32;

    err_code = nrf_drv_timer_init(&timer_inst_t5ms,
                                  &timer_cfg,
                                  t5ms_timer_event_handler);
    APP_ERROR_CHECK(err_code);

    time_ticks = nrf_drv_timer_ms_to_ticks(&timer_inst_t5ms, 5);

    nrf_drv_timer_extended_compare(&timer_inst_t5ms,
                                   NRF_TIMER_CC_CHANNEL0,
                                   time_ticks,
                                   NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                   true);

    nrf_drv_timer_enable(&timer_inst_t5ms);
    ////<<<<TIMER init

    

     //fm_set_duty(tone_array[tone_member]);
     tone_member++;

    //>>>GPIO init
    nrf_gpio_cfg_output(3);
     
       nrf_drv_timer_disable(&timer_inst_freq);
  nrf_drv_timer_clear(&timer_inst_freq);
    nrf_drv_timer_extended_compare(&timer_inst_freq,
                                 NRF_TIMER_CC_CHANNEL0,
                                 tone_array[tone_member],
                                 NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                 false);

    nrf_drv_timer_enable(&timer_inst_freq);
   

    //<<<GPIO init

    while (1)
    {
        __WFI();
    }
}

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

1x000 — Wed, 13 Oct 2021 19:51:18 GMT

This capture from my previous post was taken with the only CLEAR task.

I've just tried it with both nrf_drv_timer_disable(&timer_inst_freq) and nrf_drv_timer_clear(&timer_inst_freq)
Here is the result

The pauses are still present. But they are getting longer and shorter. On this screen on the left side pauses are about 625μs long (when normal wave must be about 310μs). On the right side, pauses are about 316μs (almost invisible)

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

Sigurd — Wed, 13 Oct 2021 15:23:55 GMT

[quote user="1x000"]I tested with correct bounds and if I didn't perform a CLEAR task there are 4ms pauses.[/quote][quote user="1x000"]They are caused by Counter overflow? Also, I noticed that pauses only appear when both timers are triggered at the same time. Why this is so?[/quote]

No, not overflow, but nrf_drv_timer_extended_compare() disables the shorts briefly, in order to set the new shorts mask specified in nrf_drv_timer_extended_compare(), so then there is a chance that the CC event triggers at the same time the shorts are disabled, and if that happens, then it's not cleared automatically, so you should therefore trigger the clear task manually.

[quote user="1x000"]This time there are no 4ms pauses, which is good. But as before we got a little pause on each 5ms tick.[/quote]

Was this with disabling the timer and clearing, or is this with only clearing?

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

1x000 — Thu, 07 Oct 2021 07:10:13 GMT

Thanks for pointing on that! Can't believe that I can miss that.

I tested with correct bounds and if I didn't perform a CLEAR task there are 4ms pauses.

They are caused by Counter overflow? Also, I noticed that pauses only appear when both timers are triggered at the same time. Why this is so?

The second test was with the CLEAR task on each 5ms timer trigger. This time there are no 4ms pauses, which is good. But as before we got a little pause on each 5ms tick.

So now we have 2 situations but none of them suits our needs. Any ideas?

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

Sigurd — Tue, 05 Oct 2021 23:16:38 GMT

Looks like your array index is out of bounds. (tone_array[1024] is not valid). Try this t5ms_timer_event_handler instead:

void t5ms_timer_event_handler(nrf_timer_event_t event_type, void *p_context)
{
    switch (event_type)
    {
        case NRF_TIMER_EVENT_COMPARE0:
            nrf_gpio_pin_toggle(3);
            fm_set_duty(tone_array[tone_member]);
            //**********tone_member table go up
            if (tone_member < (TONE_TABLE_MEMBERS-1))
            {
                tone_member++;
            }
            else if (tone_member >= (TONE_TABLE_MEMBERS-1))
            {
                tone_member = 0;
                // nrf_drv_timer_disable(&timer_inst_t5ms);
                // nrf_drv_timer_disable(&timer_inst_freq);
                // nrf_drv_ppi_channel_disable(m_ppi_channel);
                // nrf_drv_gpiote_out_task_disable(GPIO_FREQ_OUT);
            }
            //**********tone table go up

            //************30 sec ramp from tone table******
            if (timer_5ms_counter >= 6000)
            {
                nrf_drv_timer_disable(&timer_inst_t5ms);
                nrf_drv_timer_disable(&timer_inst_freq);
                nrf_drv_ppi_channel_disable(m_ppi_channel);
                nrf_drv_gpiote_out_task_disable(GPIO_FREQ_OUT);
            }
            timer_5ms_counter++;
            break;
    }
}

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

1x000 — Tue, 05 Oct 2021 17:20:09 GMT

Sure. I tried your suggestion but it doesn't resolve our issue.
Same 4ms pauses from time to time and shorter pauses on each tick off 5ms timer.

I tried with both disabling and clearing

void fm_set_duty(uint32_t period)
{

  nrf_drv_timer_disable(&timer_inst_freq);
  nrf_drv_timer_clear(&timer_inst_freq);
  nrf_drv_timer_extended_compare(&timer_inst_freq,
                                 NRF_TIMER_CC_CHANNEL0,
                                 period,
                                 NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                 false);
  nrf_drv_timer_enable(&timer_inst_freq);
}

and only with disabling

void fm_set_duty(uint32_t period)
{

  nrf_drv_timer_disable(&timer_inst_freq);
  nrf_drv_timer_extended_compare(&timer_inst_freq,
                                 NRF_TIMER_CC_CHANNEL0,
                                 period,
                                 NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                 false);
  nrf_drv_timer_enable(&timer_inst_freq);
}

without any luck.

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

Sigurd — Tue, 05 Oct 2021 16:12:05 GMT

Could you try to stop the timer when setting the new CC value, and see if that helps?

void fm_set_duty(uint32_t period)
{

  nrf_drv_timer_disable(&timer_inst_freq);
  nrf_drv_timer_clear(&timer_inst_freq);
  nrf_drv_timer_extended_compare(&timer_inst_freq,
                                 NRF_TIMER_CC_CHANNEL0,
                                 period,
                                 NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                 false);
  nrf_drv_timer_enable(&timer_inst_freq);

}

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

1x000 — Fri, 01 Oct 2021 18:34:49 GMT

Sorry for the typo in frequency.
My freq_timer_event_handler() is just empty. As In some examples on SDK.

void freq_timer_event_handler(nrf_timer_event_t event_type, void *p_context)
{
}

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

Steve77 — Fri, 01 Oct 2021 17:49:18 GMT

Thank you for reviewing this issue. This is a simple operation of a timer. It has a 16 MHz input and we give it a CC value to divide the frequency by a fixed number. For example, if we wanted to generate a 1,250 Hz signal, we would divide the 16 MHz by 3200h (12,800 decimal) to get that frequency. Then every 5.0 mS we may want to get a different frequency, so we will update the CC value to give us the next frequency that we want.

You are correct in that we are generating frequencies in the 1,000 Hz to 2,000 Hz range. The current program is trying to generate frequencies in the 1,250 Hz to 1,750 Hz range. The original post has a typo in the frequency requirements.

This is much more simple that what the Nordic Thingy:52 does to generate audio tones to the speaker with the demo software. We just want to update the timer every 5.0 mS and get a new frequency without interruption or alteration of the signal. The frequencies that we want are just 50% duty cycle square waves in that frequency range. We have had success in doing this on several microcontroller products, including another ARM Cortex M4.

The specifics of the freq_timer_event_handler will have to be addressed by the software engineer. Once again, thank you for your help.

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

Sigurd — Fri, 01 Oct 2021 12:10:31 GMT

Hi,

1) how does your function freq_timer_event_handler() look like? I tried building your code, but this function was missing.

[quote user=""](from 1250 kHz to 1750 kHz)[/quote]

Is this correct? or is it actually from 1.250 kHz to 1.750 kHz ?

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

1x000 — Thu, 30 Sep 2021 18:19:07 GMT

Thanks for the suggestion. In search of a problem, I made little modifications to the code just to make few loops of frequency output.

Your suggestion added smaller pauses (highlighted on screenshot) on each 5ms timer tick and didn't avoid all 4ms dropouts.

My current code:

#include <stdbool.h>
#include <stdint.h>
#include "nrf.h"
#include "nrf_drv_timer.h"
#include "nrf_drv_ppi.h"
#include "nrf_drv_gpiote.h"
#include "nrf_gpiote.h"
#include "nrf_gpio.h"
#include "app_error.h"
#include "nrf_pwr_mgmt.h"
#include "tone_array.h"

#define GPIO_FREQ_OUT 4
static const nrf_drv_timer_t timer_inst_t5ms = NRF_DRV_TIMER_INSTANCE(1); //!don't use TIMER0 with softdevice
static const nrf_drv_timer_t timer_inst_freq = NRF_DRV_TIMER_INSTANCE(3); //!don't use TIMER0 with softdevice
static nrf_ppi_channel_t     m_ppi_channel;
uint16_t tone_member = 1;
uint32_t timer_5ms_counter = 0;

/**
 * @brief Handler for timer events.
 */
void t5ms_timer_event_handler(nrf_timer_event_t event_type, void *p_context)
{
    switch (event_type)
    {
        case NRF_TIMER_EVENT_COMPARE0:
            nrf_gpio_pin_toggle(3);
            fm_set_duty(tone_array[tone_member]);
            //**********tone_member table go up
            if (tone_member < TONE_TABLE_MEMBERS)
            {
                tone_member++;
            }
            else if (tone_member >= TONE_TABLE_MEMBERS)
            {
                tone_member = 0;
                // nrf_drv_timer_disable(&timer_inst_t5ms);
                // nrf_drv_timer_disable(&timer_inst_freq);
                // nrf_drv_ppi_channel_disable(m_ppi_channel);
                // nrf_drv_gpiote_out_task_disable(GPIO_FREQ_OUT);
            }
            //**********tone table go up

            //************30 sec ramp from tone table******
            if (timer_5ms_counter >= 6000)
            {
                nrf_drv_timer_disable(&timer_inst_t5ms);
                nrf_drv_timer_disable(&timer_inst_freq);
                nrf_drv_ppi_channel_disable(m_ppi_channel);
                nrf_drv_gpiote_out_task_disable(GPIO_FREQ_OUT);
            }
            timer_5ms_counter++;
            break;
    }
}

void fm_set_duty(uint32_t period)
{
    nrf_drv_timer_extended_compare(&timer_inst_freq,
                                 NRF_TIMER_CC_CHANNEL0,
                                 period,
                                 NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                 false);
    nrf_drv_timer_clear(&timer_inst_freq);
}

/**
 * @brief Function for main application entry.
 */
int main(void)
{
    uint32_t time_ticks;
    uint32_t err_code = NRF_SUCCESS;

    err_code = nrf_drv_ppi_init();
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_gpiote_init();
    APP_ERROR_CHECK(err_code);

    //>>>GPIOTE init
    nrf_drv_gpiote_out_config_t config = GPIOTE_CONFIG_OUT_TASK_TOGGLE(false);

    err_code = nrf_drv_gpiote_out_init(GPIO_FREQ_OUT, &config);
    APP_ERROR_CHECK(err_code);
    //<<<GPIOTE init

    ////>>>TIMER init
    nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
    timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_16;

    err_code = nrf_drv_timer_init(&timer_inst_freq, &timer_cfg, freq_timer_event_handler);
    APP_ERROR_CHECK(err_code);

    //nrf_drv_timer_extended_compare(&timer_inst_freq,
    //                               NRF_TIMER_CC_CHANNEL0,
    //                               tone_array[0],
    //                               NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
    //                               false);
    fm_set_duty(tone_array[0]);
    ////<<<<TIMER init

    //>>>PPI init
    err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
    APP_ERROR_CHECK(err_code);

    uint32_t compare_evt_addr;
    uint32_t gpiote_task_addr;
    compare_evt_addr = nrf_drv_timer_event_address_get(&timer_inst_freq, NRF_TIMER_EVENT_COMPARE0);
    gpiote_task_addr = nrf_drv_gpiote_out_task_addr_get(GPIO_FREQ_OUT);

    err_code = nrf_drv_ppi_channel_assign(m_ppi_channel, compare_evt_addr, gpiote_task_addr);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);
    APP_ERROR_CHECK(err_code);

    nrf_drv_gpiote_out_task_enable(GPIO_FREQ_OUT);
    //<<<PPI init

    ////>>>TIMER init
    timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_32;

    err_code = nrf_drv_timer_init(&timer_inst_t5ms,
                                  &timer_cfg,
                                  t5ms_timer_event_handler);
    APP_ERROR_CHECK(err_code);

    time_ticks = nrf_drv_timer_ms_to_ticks(&timer_inst_t5ms, 5);

    nrf_drv_timer_extended_compare(&timer_inst_t5ms,
                                   NRF_TIMER_CC_CHANNEL0,
                                   time_ticks,
                                   NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                   true);

    nrf_drv_timer_enable(&timer_inst_t5ms);
    ////<<<<TIMER init

    nrf_drv_timer_enable(&timer_inst_freq);

    //>>>GPIO init
    nrf_gpio_cfg_output(3);
    //<<<GPIO init

    while (1)
    {
        __WFI();
    }
}

Even if clearing helped, these pauses on each 5ms are definitely not acceptable for our application. Do you have other suggestions?

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

Sigurd — Thu, 30 Sep 2021 15:10:01 GMT

Hi,

Could you try this modify your fm_set_duty() function so it looks like this, and see if that helps?

void fm_set_duty(uint32_t period)
{
    nrf_drv_timer_extended_compare(&timer_inst_freq,
                                 NRF_TIMER_CC_CHANNEL0,
                                 period,
                                 NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                 false);
      nrf_drv_timer_clear(&timer_inst_freq);
}

RE: nRF52 TIMER PPI GPIOTE dropouts/pauses issue

Steve77 — Tue, 28 Sep 2021 17:12:12 GMT

It would be much appreciated if someone from Nordic could help out on this issue. This is everyday use of a timer that we have performed on Cortex M4 processors before. We simply want to generate variable frequencies every 5 milliseconds. For some reason, intermittently, the timer either stops, gets reset or goes into an unknown mode. This is a commercial application that we are developing for production.