115 lines
2.6 KiB
Go
115 lines
2.6 KiB
Go
package sysfs
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import (
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"fmt"
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"os"
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"strconv"
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"syscall"
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)
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const (
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// IN gpio direction
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IN = "in"
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// OUT gpio direction
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OUT = "out"
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// HIGH gpio level
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HIGH = 1
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// LOW gpio level
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LOW = 0
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// GPIOPATH default linux gpio path
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GPIOPATH = "/sys/class/gpio"
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)
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// DigitalPin is the interface for sysfs gpio interactions
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type DigitalPin interface {
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// Unexport unexports the pin and releases the pin from the operating system
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Unexport() error
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// Export exports the pin for use by the operating system
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Export() error
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// Read reads the current value of the pin
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Read() (int, error)
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// Direction sets the direction for the pin
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Direction(string) error
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// Write writes to the pin
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Write(int) error
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}
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type digitalPin struct {
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pin string
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label string
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}
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// NewDigitalPin returns a DigitalPin given the pin number and an optional sysfs pin label.
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// If no label is supplied the default label will prepend "gpio" to the pin number,
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// eg. a pin number of 10 will have a label of "gpio10"
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func NewDigitalPin(pin int, v ...string) DigitalPin {
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d := &digitalPin{pin: strconv.Itoa(pin)}
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if len(v) > 0 {
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d.label = v[0]
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} else {
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d.label = "gpio" + d.pin
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}
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return d
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}
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func (d *digitalPin) Direction(dir string) error {
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_, err := writeFile(fmt.Sprintf("%v/%v/direction", GPIOPATH, d.label), []byte(dir))
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return err
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}
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func (d *digitalPin) Write(b int) error {
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_, err := writeFile(fmt.Sprintf("%v/%v/value", GPIOPATH, d.label), []byte(strconv.Itoa(b)))
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return err
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}
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func (d *digitalPin) Read() (n int, err error) {
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buf, err := readFile(fmt.Sprintf("%v/%v/value", GPIOPATH, d.label))
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if err != nil {
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return 0, err
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}
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return strconv.Atoi(string(buf[0]))
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}
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func (d *digitalPin) Export() error {
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if _, err := writeFile(GPIOPATH+"/export", []byte(d.pin)); err != nil {
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// If EBUSY then the pin has already been exported
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if err.(*os.PathError).Err != syscall.EBUSY {
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return err
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}
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}
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return nil
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}
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func (d *digitalPin) Unexport() error {
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if _, err := writeFile(GPIOPATH+"/unexport", []byte(d.pin)); err != nil {
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// If EINVAL then the pin is reserved in the system and can't be unexported
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if err.(*os.PathError).Err != syscall.EINVAL {
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return err
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}
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}
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return nil
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}
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var writeFile = func(path string, data []byte) (i int, err error) {
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file, err := OpenFile(path, os.O_WRONLY, 0644)
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defer file.Close()
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if err != nil {
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return
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}
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return file.Write(data)
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}
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var readFile = func(path string) ([]byte, error) {
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file, err := OpenFile(path, os.O_RDONLY, 0644)
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defer file.Close()
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if err != nil {
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return make([]byte, 0), err
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}
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buf := make([]byte, 2)
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_, err = file.Read(buf)
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return buf, err
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}
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