func (p *pwmPin) enable(val string) (err error) {
	_, err = writeFile(pwmEnablePath(p.pin), []byte(val))
	return
}
enable writes value to pwm enable path
package edison
import "strconv"
func pwmPath() string {
	return "/sys/class/pwm/pwmchip0"
}
func pwmExportPath() string {
	return pwmPath() + "/export"
}
func pwmUnExportPath() string {
	return pwmPath() + "/unexport"
}
func pwmDutyCyclePath(pin string) string {
	return pwmPath() + "/pwm" + pin + "/duty_cycle"
}
func pwmPeriodPath(pin string) string {
	return pwmPath() + "/pwm" + pin + "/period"
}
func pwmEnablePath(pin string) string {
	return pwmPath() + "/pwm" + pin + "/enable"
}
type pwmPin struct {
	pin string
}
func newPwmPin(pin int) *pwmPin {
	return &pwmPin{pin: strconv.Itoa(pin)}
}