mirror of
https://github.com/kidoman/embd
synced 2024-10-31 23:38:44 +01:00
262 lines
5.1 KiB
Go
262 lines
5.1 KiB
Go
|
// PWM support on the BBB.
|
||
|
|
||
|
package bbb
|
||
|
|
||
|
import (
|
||
|
"errors"
|
||
|
"fmt"
|
||
|
"os"
|
||
|
"path"
|
||
|
"strconv"
|
||
|
"time"
|
||
|
|
||
|
"github.com/golang/glog"
|
||
|
"github.com/kidoman/embd"
|
||
|
"github.com/kidoman/embd/util"
|
||
|
)
|
||
|
|
||
|
const (
|
||
|
// PWMDefaultPolarity represents the default polarity (Positve or 1) for pwm.
|
||
|
PWMDefaultPolarity = embd.Positive
|
||
|
|
||
|
// PWMDefaultDuty represents the default duty (0ns) for pwm.
|
||
|
PWMDefaultDuty = 0
|
||
|
|
||
|
// PWMDefaultPeriod represents the default period (500000ns) for pwm. Equals 2000 Hz.
|
||
|
PWMDefaultPeriod = 500000
|
||
|
|
||
|
// PWMMaxPulseWidth represents the max period (1000000000ns) supported by pwm. Equals 1 Hz.
|
||
|
PWMMaxPulseWidth = 1000000000
|
||
|
)
|
||
|
|
||
|
type pwmPin struct {
|
||
|
n string
|
||
|
|
||
|
drv embd.GPIODriver
|
||
|
|
||
|
period int
|
||
|
polarity embd.Polarity
|
||
|
|
||
|
dutyf *os.File
|
||
|
periodf *os.File
|
||
|
polarityf *os.File
|
||
|
|
||
|
initialized bool
|
||
|
}
|
||
|
|
||
|
func newPWMPin(pd *embd.PinDesc, drv embd.GPIODriver) embd.PWMPin {
|
||
|
return &pwmPin{n: pd.ID, drv: drv}
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) N() string {
|
||
|
return p.n
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) id() string {
|
||
|
return "bone_pwm_" + p.n
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) init() error {
|
||
|
if p.initialized {
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
if err := p.ensurePWMEnabled(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
if err := p.ensurePinEnabled(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
basePath, err := p.basePath()
|
||
|
if err != nil {
|
||
|
return err
|
||
|
}
|
||
|
if err := p.ensurePeriodFileExists(basePath, 500*time.Millisecond); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
if p.periodf, err = p.periodFile(basePath); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
if p.dutyf, err = p.dutyFile(basePath); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
if p.polarityf, err = p.polarityFile(basePath); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
p.initialized = true
|
||
|
|
||
|
if err := p.reset(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) ensurePWMEnabled() error {
|
||
|
return ensureFeatureEnabled("am33xx_pwm")
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) ensurePinEnabled() error {
|
||
|
return ensureFeatureEnabled(p.id())
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) ensurePinDisabled() error {
|
||
|
return ensureFeatureDisabled(p.id())
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) basePath() (string, error) {
|
||
|
pattern := "/sys/devices/ocp.*/pwm_test_" + p.n + ".*"
|
||
|
return embd.FindFirstMatchingFile(pattern)
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) openFile(path string) (*os.File, error) {
|
||
|
return os.OpenFile(path, os.O_WRONLY, os.ModeExclusive)
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) ensurePeriodFileExists(basePath string, d time.Duration) error {
|
||
|
path := p.periodFilePath(basePath)
|
||
|
timeout := time.After(d)
|
||
|
|
||
|
for {
|
||
|
select {
|
||
|
case <-timeout:
|
||
|
return errors.New("embd: period file not found before timeout")
|
||
|
default:
|
||
|
if _, err := os.Stat(path); err == nil {
|
||
|
return nil
|
||
|
}
|
||
|
}
|
||
|
|
||
|
// We are looping, wait a bit.
|
||
|
time.Sleep(10 * time.Millisecond)
|
||
|
}
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) periodFilePath(basePath string) string {
|
||
|
return path.Join(basePath, "period")
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) periodFile(basePath string) (*os.File, error) {
|
||
|
return p.openFile(p.periodFilePath(basePath))
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) dutyFile(basePath string) (*os.File, error) {
|
||
|
return p.openFile(path.Join(basePath, "duty"))
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) polarityFile(basePath string) (*os.File, error) {
|
||
|
return p.openFile(path.Join(basePath, "polarity"))
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) SetPeriod(ns int) error {
|
||
|
if err := p.init(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
if ns > PWMMaxPulseWidth {
|
||
|
return fmt.Errorf("embd: pwm period for %v is out of bounds (must be =< %vns)", p.n, PWMMaxPulseWidth)
|
||
|
}
|
||
|
|
||
|
_, err := p.periodf.WriteString(strconv.Itoa(ns))
|
||
|
if err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
p.period = ns
|
||
|
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) SetDuty(ns int) error {
|
||
|
if err := p.init(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
if ns > PWMMaxPulseWidth {
|
||
|
return fmt.Errorf("embd: pwm duty %v for pin %v is out of bounds (must be =< %vns)", p.n, PWMMaxPulseWidth)
|
||
|
}
|
||
|
|
||
|
if ns > p.period {
|
||
|
return fmt.Errorf("embd: pwm duty %v for pin %v is greater than the period %v", ns, p.n, p.period)
|
||
|
}
|
||
|
|
||
|
_, err := p.dutyf.WriteString(strconv.Itoa(ns))
|
||
|
if err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) SetMicroseconds(us int) error {
|
||
|
if err := p.init(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
if p.period != 20000000 {
|
||
|
glog.Warningf("embd: pwm pin %v has freq %v hz. recommended 50 hz for servo mode", 1000000000/p.period)
|
||
|
}
|
||
|
duty := us * 1000 // in nanoseconds
|
||
|
if duty > p.period {
|
||
|
return fmt.Errorf("embd: calculated pwm duty %vns for pin %v (servo mode) is greater than the period %vns", duty, p.n, p.period)
|
||
|
}
|
||
|
return p.SetDuty(duty)
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) SetAnalog(value byte) error {
|
||
|
duty := util.Map(int64(value), 0, 255, 0, int64(p.period))
|
||
|
return p.SetDuty(int(duty))
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) SetPolarity(pol embd.Polarity) error {
|
||
|
if err := p.init(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
_, err := p.polarityf.WriteString(strconv.Itoa(int(pol)))
|
||
|
if err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
p.polarity = pol
|
||
|
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) reset() error {
|
||
|
if err := p.SetPolarity(embd.Positive); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
if err := p.SetDuty(PWMDefaultDuty); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
if err := p.SetPeriod(PWMDefaultPeriod); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
func (p *pwmPin) Close() error {
|
||
|
if err := p.drv.Unregister(p.n); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
if !p.initialized {
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
if err := p.reset(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
if err := p.ensurePinDisabled(); err != nil {
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
p.initialized = false
|
||
|
|
||
|
return nil
|
||
|
}
|