README
¶
rangesensor
A package to take a distance measurement from an HC-SR04 ultrasonic range sensor.
Basic Usage
package main
import (
"fmt"
"os"
"time"
"github.com/asjoyner/rangesensor"
)
func main() {
s, err := rangesensor.New("22", "23")
if err != nil {
fmt.Println("could not configure pin: ", err)
os.Exit(1)
}
for {
distance, err := s.MeasureDistance()
if err != nil {
fmt.Println(err)
} else {
fmt.Printf("Distance: %5.2f cm", distance.InCentimeters())
fmt.Printf(" (%d us)\n", distance.InMicroseconds())
}
time.Sleep(time.Duration(250) * time.Millisecond)
}
}
Credit
This takes inspiration from both of these repositories.
Both of those are based on github.com/stianeikeland/go-rpio. I chose to reimplement a similar basic mechanic on top of the periph.io/x/periph/conn/gpio library so it would be easier to add testing, use the more sysfs kernel API, and leverage the associated interrupt-based edge detection.
Documentation
¶
Overview ¶
Package rangesensor facilitates measuring distance with an HC-SR04 ultrasonic ranging module.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func TimeToCentimeters ¶
TimeToCentimeters takes a distance measurement in microseconds and converts that into a distance measurement in centimeters using a series of transparent assumptions. I do this tediously in long-hand, so if I've made some mistake others can notice and correct it. :)
At the end of the day, this function divides by two and multiplies by 0.0344, which aligns with the datasheet's suggestion to just divide by 58 to get centimeters.
Types ¶
type Measurement ¶
type Measurement struct {
// contains filtered or unexported fields
}
Measurement expresses a sensor measurement and facilitates conversion to various units.
func (*Measurement) InCentimeters ¶
func (r *Measurement) InCentimeters() float32
InCentimeters converts the time of flight measurement into centimeters.
func (*Measurement) InInches ¶
func (r *Measurement) InInches() float32
InInches converts the time of flight measurement into inches.
func (*Measurement) InMicroseconds ¶
func (r *Measurement) InMicroseconds() int64
InMicroseconds returns the raw time of flight measurement.
func (*Measurement) InMilliseconds ¶
func (r *Measurement) InMilliseconds() int64
InMilliseconds returns the raw time of flight measurement.
func (*Measurement) Trustworthy ¶
func (r *Measurement) Trustworthy() bool
Trustworthy indicates the reliability of the measurement. The datasheet indicates claims the module can render distances out to 400cm, but the modules I have experience with are not accurate beyond 200cm. More importantly, a failed read will often return a spurious result, in the 1k+ cm range.
type Sensor ¶
Sensor represents an HC-SR04 ultrasonic ranging module.
Datasheet: https://cdn.sparkfun.com/datasheets/Sensors/Proximity/HCSR04.pdf
func New ¶
New initializes and returns a Sensor object.
Echo is the name of the GPIO pin connected to the module's "Echo" pin. Trigger is the name of the GPIO pin connected to the module's "Trig" pin.
Both names should be in the format expected by this module's ByName function periph.io/x/periph/conn/gpio/gpioreg
For a RaspberryPi, this corresponds to the BCM pin number as a string.
func (*Sensor) MeasureDistance ¶
func (s *Sensor) MeasureDistance() (*Measurement, error)
MeasureDistance returns a distance measurement from the sensor.
Source Files