srf04 ultra sonic range finder

Device driver for the srf04 ultra sonic range finder.

enum @159

SRF04_OK =  0

exit without error

SRF04_ERR_INVALID = -1

error no valid measurement available

SRF04_ERR_MEASURING = -2

error sensor is measuring

SRF04_ERR_GPIO = -3

error initializing gpio

int srf04_init(srf04_t * dev, const srf04_params_t * params)

Initialize gpio and interrupt.

Parameters

dev:device descriptor of sensor to initialize params:init param struct holding gpio trigger and echo pins

Return values

• SRF04_OK on success
• SRF04_GPIO on gpio init failure

void srf04_trigger(const srf04_t * dev)

Triggers measurement.

Parameters

dev:device descriptor of sensor

int srf04_read(const srf04_t * dev)

Returns time of flight in ms.

Note

should not be invoked within 50 ms after triggering

Parameters

dev:device descriptor of sensor

Return values

• time of flight in ms
• SRF04_MEASURING if measurement is in progress
• SRF04_INVALID if no valid measurement is available

int srf04_get_distance(const srf04_t * dev)

Convenience function triggers a measurement and returns distance.

Note

This function will return after 50 ms once new data is available

Parameters

dev:device descriptor of sensor

Return values

• time of flight in mm
• SRF04_MEASURING if measurement is in progress
• SRF04_INVALID if no valid measurement is available

struct srf04_params_t

GPIO pins for srf04 device.

gpio.h::gpio_t trigger

GPIO Port the trigger pin is connected to.

gpio.h::gpio_t echo

GPIO Port the echo pin is connected to.

struct srf04_t

Device descriptor for srf04 sensor.

srf04_params_t p

GPIO Ports of device.

int distance

raw time of flight distance

uint32_t time

timestamp of trigger or echo