RE: Taking control of the capacitive touch library

ovrebekk — Tue, 06 Jun 2017 12:55:25 GMT

Hi Lola

It's good to hear you found a working solution.
If you need some inspiration for the filtering algorithm you can take a look at the old capsense example for the nRF51

It works just like you described, by using a 1M resistor to charge the sensor through a separate GPIO.

Best regards

RE: Taking control of the capacitive touch library

Lola — Fri, 02 Jun 2017 18:04:52 GMT

I found out that working with the driver directly will provide a more intimate relationship with the sensor , so I used the driver directly, and I can measure values and run my own dsp.

This code will measure every 150 ticks the values, but I must say the values are strange at the moment, I will update when I get it right !

UPDATE !

This works REALLY good, with a resistor of 1M, where you touch directly the pad. I have to mention to anyone who reads this, this will not use the COMP since it's unstable, so you need 2 pins, a digital out with a resistor into the AIN, and from the analog , exposed pad.

From here, any cool DSP can be implemented !

/* Pin used to measure capacitor charging time. */
#if USE_COMP == 0
#ifdef ADC_PRESENT
#define OUTPUT_PIN 30
#elif defined(SAADC_PRESENT)
#define OUTPUT_PIN 26
#endif
#endif

/* Time between RTC interrupts. */
 #define APP_TIMER_TICKS_TIMEOUT APP_TIMER_TICKS(150)
 #define AIN_1                   1
 #define AIN_2                   2
 #define AIN_7                   7
 #define PAD_1_MASK              (1UL << AIN_1)
 #define PAD_2_MASK              (1UL << AIN_7)
 #define PAD_ID_0                0
 #define PAD_ID_1                1



static ret_code_t clock_config(void)
{
    ret_code_t err_code;

    err_code = nrf_drv_clock_init();
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

    nrf_drv_clock_lfclk_request(NULL);

    return NRF_SUCCESS;
}


 static void csense_timeout_handler(void * p_context)
{
    ret_code_t err_code;

    err_code = nrf_drv_csense_sample();
    if (err_code != NRF_SUCCESS)
    {
        NRF_LOG_INFO("Busy.\r\n");
        return;
    }
}

  void start_app_timer(void)
{
    ret_code_t err_code;

    /* APP_TIMER definition for csense example. */
    APP_TIMER_DEF(timer_0);

    err_code = app_timer_create(&timer_0, APP_TIMER_MODE_REPEATED, csense_timeout_handler);
    APP_ERROR_CHECK(err_code);

    err_code = app_timer_start(timer_0, APP_TIMER_TICKS_TIMEOUT, NULL);
    APP_ERROR_CHECK(err_code);
}




void csense_handler(nrf_drv_csense_evt_t * p_event_struct)
{
    switch (p_event_struct->analog_channel)
    {
        case AIN_1:
        case AIN_2:
                 NRF_LOG_INFO("t:%d\r\n",p_event_struct->read_value);
                 break;
        case AIN_7:

                 NRF_LOG_INFO("t:%d\r\n",p_event_struct->read_value);
                 break;
 
        default:
            break;
    }
}


void csense_initialize(void)
{
    ret_code_t err_code;

    nrf_drv_csense_config_t csense_config = { 0 };

#if USE_COMP == 0
    csense_config.output_pin = OUTPUT_PIN;
#endif

    err_code = nrf_drv_csense_init(&csense_config, csense_handler);
    APP_ERROR_CHECK(err_code);

    nrf_drv_csense_channels_enable(PAD_1_MASK | PAD_2_MASK);
}