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126 lines
2.9 KiB
Go
126 lines
2.9 KiB
Go
package sysfs
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import (
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"os"
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"strconv"
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)
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// PWMPin is the interface for sysfs PWM interactions
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type PWMPin interface {
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// Export exports the pin for use by the operating system
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Export() error
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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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// Enable enables/disables the PWM pin
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Enable(val string) (err error)
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// Period returns the current PWM period for pin
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Period() (period string, err error)
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// WriteDuty writes the duty cycle to the pin
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WriteDuty(duty string) (err error)
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}
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type pwmPin struct {
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pin string
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Chip string
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write func(path string, data []byte) (i int, err error)
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read func(path string) ([]byte, error)
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}
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// NewPwmPin returns a new pwmPin
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func NewPwmPin(pin int) *pwmPin {
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return &pwmPin{
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pin: strconv.Itoa(pin),
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Chip: "0",
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read: readPwmFile,
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write: writePwmFile}
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}
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// Export writes pin to pwm export path
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func (p *pwmPin) Export() (err error) {
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_, err = p.write(p.pwmExportPath(), []byte(p.pin))
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return
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}
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// Unexport writes pin to pwm unexport path
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func (p *pwmPin) Unexport() (err error) {
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_, err = p.write(p.pwmUnexportPath(), []byte(p.pin))
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return
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}
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// Enable writes value to pwm enable path
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func (p *pwmPin) Enable(val string) (err error) {
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_, err = p.write(p.pwmEnablePath(), []byte(val))
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return
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}
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// Period reads from pwm period path and returns value
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func (p *pwmPin) Period() (period string, err error) {
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buf, err := p.read(p.pwmPeriodPath())
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if err != nil {
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return
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}
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return string(buf), nil
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}
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// WriteDuty writes value to pwm duty cycle path
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func (p *pwmPin) WriteDuty(duty string) (err error) {
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_, err = p.write(p.pwmDutyCyclePath(), []byte(duty))
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return
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}
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// pwmPath returns pwm base path
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func (p *pwmPin) pwmPath() string {
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return "/sys/class/pwm/pwmchip" + p.Chip
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}
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// pwmExportPath returns export path
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func (p *pwmPin) pwmExportPath() string {
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return p.pwmPath() + "/export"
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}
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// pwmUnexportPath returns unexport path
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func (p *pwmPin) pwmUnexportPath() string {
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return p.pwmPath() + "/unexport"
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}
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// pwmDutyCyclePath returns duty_cycle path for specified pin
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func (p *pwmPin) pwmDutyCyclePath() string {
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return p.pwmPath() + "/pwm" + p.pin + "/duty_cycle"
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}
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// pwmPeriodPath returns period path for specified pin
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func (p *pwmPin) pwmPeriodPath() string {
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return p.pwmPath() + "/pwm" + p.pin + "/period"
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}
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// pwmEnablePath returns enable path for specified pin
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func (p *pwmPin) pwmEnablePath() string {
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return p.pwmPath() + "/pwm" + p.pin + "/enable"
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}
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func writePwmFile(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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func readPwmFile(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, 200)
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var i int
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i, err = file.Read(buf)
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if i == 0 {
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return buf, err
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}
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return buf[:i], err
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}
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