using PWM to measure input period and pulse width

[Timothy]

I have an input signal of unknown period and pulse width on a GPIO. I want to use the PWM capture capabilities to  retrieve those parameters.

I see in the documentation there is

pwm_pin_configure_capture, pwm_pin_enable_capture, pwm_pin_disable_capture, pwm_pin_capture_usec, pwm_capture_callback_handler

I did not see an example how to use these. could you show me a simple example of what I need to do to  get the period and pulse width from an input signal using a PWM. The functions seem to be exactly what I need but the implementation is not clear in the documentation and I am getting a lot of compile errors. I am sure it is something simple I am missing. I appreciate any help you can give.

[Timothy]

Smit

below is the code that I am using to measure the output of a Hall effect sensor. Their is a pulse width of 30 - 200us.

typedef struct
{
uint32_t pulseWidth; //!< pulse width in us
uint32_t period; //!< period in us
} sensorDataStruct;
sensorDataStruct sensorData[SENSOR_BUFFER_SIZE];
iuint16_t sensorDataIn;
uint16_t sensorDataOut;
uint16_t sensorDataCount;
nt32_t inputPulseWidth;
int32_t inputPeriod;
void hallSensorCallback(struct device *dev, struct gpio_callback *cb, uint32_t pins);
void configurePins();

main()

{

...

...

sensorDataIn = 0;
sensorDataOut = 0;
sensorDataCount = 0;
timer_init();
configurePins();

NRF_TIMER1->TASKS_START = 1;
...

...

}

void timer_init()
{
NRF_TIMER1->TASKS_STOP = 1;
NRF_TIMER1->MODE = TIMER_MODE_MODE_Timer;
NRF_TIMER1->PRESCALER = 4; // Fhck / 2^4 = 1us
// NRF_TIMER1->CC[0] = 62500; // 62500 - 1s

NRF_TIMER1->BITMODE = (TIMER_BITMODE_BITMODE_32Bit << TIMER_BITMODE_BITMODE_Pos);

NRF_TIMER1->TASKS_CLEAR = 1;
// NRF_TIMER1->INTENSET = (TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos);

NRF_TIMER1->EVENTS_COMPARE[0] = 0;
}

void hallSensorCallback(struct device *dev, struct gpio_callback *cb, uint32_t pins)
{
int pin;

pin = gpio_pin_get(dev, HALL_SENSOR_PIN);
gpio_pin_set(dev,LED3_PIN,pin);
if(pin == 0)
{
NRF_TIMER1->TASKS_CAPTURE[0] = 1;
inputPeriod = NRF_TIMER1->CC[0];
NRF_TIMER1->TASKS_CLEAR = 1;
if(sensorDataCount == 0) /* check if first pulse width measured */
return;
if( sensorDataIn == 0 )
sensorData[SENSOR_BUFFER_SIZE - 1].period = inputPeriod;
else
sensorData[sensorDataIn - 1].period = inputPeriod;
}
else
{
NRF_TIMER1->TASKS_CAPTURE[0] = 1;
inputPulseWidth = NRF_TIMER1->CC[0];
if(inputPulseWidth >= 1000) /* check if valid pulse width */
return;
if(sensorDataCount < SENSOR_BUFFER_SIZE)
{
sensorData[sensorDataIn++].pulseWidth = inputPulseWidth;
sensorData[sensorDataIn - 1].period = 0;
if(sensorDataIn == SENSOR_BUFFER_SIZE) /* is it wrap around */
sensorDataIn = 0;
sensorDataCount++;
}
}
}

void configurePins()
{
/* configure output pins */
// gpio_pin_configure(gpioPtr, LED3_PIN,GPIO_OUTPUT | GPIO_ACTIVE_HIGH | GPIO_PULL_UP);
gpio_pin_configure(gpioPtr, LED3_PIN,GPIO_OUTPUT );

/* configure input pins */
gpio_pin_configure(gpioPtr, HALL_SENSOR_PIN,GPIO_INPUT | GPIO_ACTIVE_LOW );

/* configure interrupt callbacks */
gpio_init_callback(&gpio_hall_sensor_cb, (gpio_callback_handler_t)hallSensorCallback, BIT(HALL_SENSOR_PIN));
gpio_add_callback(gpioPtr, &gpio_hall_sensor_cb);
}