nRF52 TIMER PPI GPIOTE dropouts/pauses issue

[1x000]

Hi. I'm trying to output frequency (in the 1,250 Hz to 1,750 Hz range) on GPIO. Each frequency should be outputted for 5ms time. For that, I use 2 TIMERs: one for 5ms counter and one for frequency output + PPI + GPIOTE. I have a lookup array with "tones" for certain frequencies. When the 5ms timer fires up I pass the next value from the array to the frequency output timer as the CC value.

The problem is when frequency outputs I can see some dropouts in frequency with logic analyzer. These dropouts occur in different moments but in most cases, they last about 4ms.

I expect to frequency change without any dropouts and pauses. What I'm doing wrong?

Here is the code
(based on ...\nRF5_SDK_17.0.2_d674dde\examples\peripheral\timer)

#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
        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);
}

/**
 * @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);
    ////<<<<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();
    }
}

const uint16_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
};

My setup:
nRF52832 (NRF52 DK)
SDK 17.0.2
SES 5.5
SoftDevice none (but in future this code must with it)

Logic analyzer screenshots (bottom channel is a visualization of the 5ms timer)




Hope you can help me. I'm out of ideas.

[Steve77]

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.