105 lines
2.3 KiB
Go
105 lines
2.3 KiB
Go
package raspi
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import (
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"errors"
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"fmt"
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"os"
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"gobot.io/x/gobot"
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"gobot.io/x/gobot/sysfs"
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)
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// PWMPin is the Raspberry Pi implementation of the PWMPinner interface.
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// It uses Pi Blaster.
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type PWMPin struct {
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pin string
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dc uint32
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period uint32
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}
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// NewPwmPin returns a new PWMPin
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func NewPWMPin(pin string) *PWMPin {
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return &PWMPin{
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pin: pin}
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}
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// Export exports the pin for use by the Raspberry Pi
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func (p *PWMPin) Export() error {
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return nil
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}
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// Unexport unexports the pin and releases the pin from the operating system
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func (p *PWMPin) Unexport() error {
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return p.piBlaster(fmt.Sprintf("release %v\n", p.pin))
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}
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// Enable enables/disables the PWM pin
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func (p *PWMPin) Enable(e bool) (err error) {
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return nil
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}
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// Polarity returns the polarity either normal or inverted
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func (p *PWMPin) Polarity() (polarity string, err error) {
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return "normal", nil
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}
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// InvertPolarity does not do anything when using PiBlaster
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func (p *PWMPin) InvertPolarity(invert bool) (err error) {
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return nil
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}
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// Period returns the current PWM period for pin
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func (p *PWMPin) Period() (period uint32, err error) {
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if p.period == 0 {
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return p.period, errors.New("Raspi PWM pin period not set")
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}
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return p.period, nil
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}
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// SetPeriod uses PiBlaster setting and cannot be changed once set
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func (p *PWMPin) SetPeriod(period uint32) (err error) {
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if p.period != 0 {
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return errors.New("Cannot set the period of individual PWM pins on Raspi")
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}
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p.period = period
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return nil
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}
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// DutyCycle returns the duty cycle for the pin
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func (p *PWMPin) DutyCycle() (duty uint32, err error) {
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return p.dc, nil
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}
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// SetDutyCycle writes the duty cycle to the pin
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func (p *PWMPin) SetDutyCycle(duty uint32) (err error) {
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if p.period == 0 {
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return errors.New("Raspi PWM pin period not set")
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}
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if duty > p.period {
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return errors.New("Duty cycle exceeds period.")
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}
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p.dc = duty
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val := gobot.FromScale(float64(p.dc), 0, float64(p.period))
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// never go below minimum allowed duty for pi blaster
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if val < 0.05 {
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val = 0.05
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}
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return p.piBlaster(fmt.Sprintf("%v=%v\n", p.pin, val))
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}
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func (p *PWMPin) piBlaster(data string) (err error) {
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fi, err := sysfs.OpenFile("/dev/pi-blaster", os.O_WRONLY|os.O_APPEND, 0644)
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defer fi.Close()
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if err != nil {
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return err
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}
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_, err = fi.WriteString(data)
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return
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}
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