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146 lines
3.2 KiB
Go
146 lines
3.2 KiB
Go
package jetson
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import (
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"errors"
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"fmt"
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"os"
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"path"
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"gobot.io/x/gobot/v2"
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"gobot.io/x/gobot/v2/system"
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)
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const (
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minimumPeriod = 5334
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minimumRate = 0.05
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)
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// PWMPin is the Jetson Nano implementation of the PWMPinner interface.
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// It uses gpio pwm.
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type PWMPin struct {
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sys *system.Accesser
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path string
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fn string
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dc uint32
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period uint32
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enabled bool
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}
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// NewPWMPin returns a new PWMPin
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// pin32 pwm0, pin33 pwm2
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func NewPWMPin(sys *system.Accesser, path string, fn string) *PWMPin {
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p := &PWMPin{
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sys: sys,
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path: path,
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fn: fn,
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}
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return p
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}
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// Export exports the pin for use by the Jetson Nano
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func (p *PWMPin) Export() error {
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return p.writeFile("export", p.fn)
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}
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// Unexport releases the pin from the operating system
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func (p *PWMPin) Unexport() error {
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return p.writeFile("unexport", p.fn)
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}
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// Enabled returns the cached enabled state of the PWM pin
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func (p *PWMPin) Enabled() (bool, error) {
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return p.enabled, nil
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}
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// SetEnabled enables/disables the PWM pin
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func (p *PWMPin) SetEnabled(e bool) error {
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if err := p.writeFile(fmt.Sprintf("pwm%s/enable", p.fn), fmt.Sprintf("%v", bool2int(e))); err != nil {
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return err
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}
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p.enabled = e
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return nil
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}
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// Polarity returns always the polarity "true" for normal
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func (p *PWMPin) Polarity() (bool, error) {
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return true, nil
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}
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// SetPolarity does not do anything when using Jetson Nano
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func (p *PWMPin) SetPolarity(bool) error {
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return nil
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}
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// Period returns the cached 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("Jetson 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 Jetson Nano setting and cannot be changed once set
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func (p *PWMPin) SetPeriod(period uint32) 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 Jetson")
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}
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// JetsonNano Minimum period
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if period < minimumPeriod {
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return errors.New("Cannot set the period more then minimum")
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}
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if err := p.writeFile(fmt.Sprintf("pwm%s/period", p.fn), fmt.Sprintf("%v", period)); err != nil {
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return err
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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 cached duty cycle for the pin
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func (p *PWMPin) DutyCycle() (uint32, 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) error {
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if p.period == 0 {
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return errors.New("Jetson 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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rate := gobot.FromScale(float64(duty), 0, float64(p.period))
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// never go below minimum allowed duty because very short duty
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if rate < minimumRate {
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duty = uint32(minimumRate * float64(p.period) / 100)
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}
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if err := p.writeFile(fmt.Sprintf("pwm%s/duty_cycle", p.fn), fmt.Sprintf("%v", duty)); err != nil {
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return err
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}
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p.dc = duty
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return nil
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}
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func (p *PWMPin) writeFile(subpath string, value string) error {
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sysfspath := path.Join(p.path, subpath)
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fi, err := p.sys.OpenFile(sysfspath, os.O_WRONLY|os.O_APPEND, 0o644)
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defer fi.Close() //nolint:staticcheck // for historical reasons
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if err != nil {
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return err
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}
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_, err = fi.WriteString(value)
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return err
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}
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func bool2int(b bool) int {
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if b {
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return 1
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}
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return 0
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}
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