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// Copyright 2016 The Periph Authors. All rights reserved.
// Use of this source code is governed under the Apache License, Version 2.0
// that can be found in the LICENSE file.
// Package gpio defines digital pins.
//
// All GPIO implementations are expected to implement PinIO but the device
// driver may accept a more specific one like PinIn or PinOut.
package gpio
import (
"errors"
"strconv"
"strings"
"time"
"periph.io/x/periph/conn/physic"
"periph.io/x/periph/conn/pin"
)
// Interfaces
// Level is the level of the pin: Low or High.
type Level bool
const (
// Low represents 0v.
Low Level = false
// High represents Vin, generally 3.3v or 5v.
High Level = true
)
func (l Level) String() string {
if l == Low {
return "Low"
}
return "High"
}
// Pull specifies the internal pull-up or pull-down for a pin set as input.
type Pull uint8
// Acceptable pull values.
const (
PullNoChange Pull = 0 // Do not change the previous pull resistor setting or an unknown value
Float Pull = 1 // Let the input float
PullDown Pull = 2 // Apply pull-down
PullUp Pull = 3 // Apply pull-up
)
const pullName = "PullNoChangeFloatPullDownPullUp"
var pullIndex = [...]uint8{0, 12, 17, 25, 31}
func (i Pull) String() string {
if i >= Pull(len(pullIndex)-1) {
return "Pull(" + strconv.Itoa(int(i)) + ")"
}
return pullName[pullIndex[i]:pullIndex[i+1]]
}
// Edge specifies if an input pin should have edge detection enabled.
//
// Only enable it when needed, since this causes system interrupts.
type Edge int
// Acceptable edge detection values.
const (
NoEdge Edge = 0
RisingEdge Edge = 1
FallingEdge Edge = 2
BothEdges Edge = 3
)
const edgeName = "NoEdgeRisingEdgeFallingEdgeBothEdges"
var edgeIndex = [...]uint8{0, 6, 16, 27, 36}
func (i Edge) String() string {
if i >= Edge(len(edgeIndex)-1) {
return "Edge(" + strconv.Itoa(int(i)) + ")"
}
return edgeName[edgeIndex[i]:edgeIndex[i+1]]
}
const (
// DutyMax is a duty cycle of 100%.
DutyMax Duty = 1 << 24
// DutyHalf is a 50% duty PWM, which boils down to a normal clock.
DutyHalf Duty = DutyMax / 2
)
// Duty is the duty cycle for a PWM.
//
// Valid values are between 0 and DutyMax.
type Duty int32
func (d Duty) String() string {
// TODO(maruel): Implement one fractional number.
return strconv.Itoa(int((d+50)/(DutyMax/100))) + "%"
}
// Valid returns true if the Duty cycle value is valid.
func (d Duty) Valid() bool {
return d >= 0 && d <= DutyMax
}
// ParseDuty parses a string and converts it to a Duty value.
func ParseDuty(s string) (Duty, error) {
percent := strings.HasSuffix(s, "%")
if percent {
s = s[:len(s)-1]
}
i64, err := strconv.ParseInt(s, 10, 32)
if err != nil {
return 0, err
}
i := Duty(i64)
if percent {
// TODO(maruel): Add support for fractional number.
if i < 0 {
return 0, errors.New("duty must be >= 0%")
}
if i > 100 {
return 0, errors.New("duty must be <= 100%")
}
return ((i * DutyMax) + 49) / 100, nil
}
if i < 0 {
return 0, errors.New("duty must be >= 0")
}
if i > DutyMax {
return 0, errors.New("duty must be <= " + strconv.Itoa(int(DutyMax)))
}
return i, nil
}
// PinIn is an input GPIO pin.
//
// It may optionally support internal pull resistor and edge based triggering.
//
// A button is semantically a PinIn. So if you are looking to read from a
// button, PinIn is the interface you are looking for.
type PinIn interface {
pin.Pin
// In setups a pin as an input.
//
// If WaitForEdge() is planned to be called, make sure to use one of the Edge
// value. Otherwise, use NoEdge to not generated unneeded hardware interrupts.
//
// Calling In() will try to empty the accumulated edges but it cannot be 100%
// reliable due to the OS (linux) and its driver. It is possible that on a
// gpio that is as input, doing a quick Out(), In() may return an edge that
// occurred before the Out() call.
In(pull Pull, edge Edge) error
// Read return the current pin level.
//
// Behavior is undefined if In() wasn't used before.
//
// In some rare case, it is possible that Read() fails silently. This happens
// if another process on the host messes up with the pin after In() was
// called. In this case, call In() again.
Read() Level
// WaitForEdge() waits for the next edge or immediately return if an edge
// occurred since the last call.
//
// Only waits for the kind of edge as specified in a previous In() call.
// Behavior is undefined if In() with a value other than NoEdge wasn't called
// before.
//
// Returns true if an edge was detected during or before this call. Return
// false if the timeout occurred or In() was called while waiting, causing the
// function to exit.
//
// Multiple edges may or may not accumulate between two calls to
// WaitForEdge(). The behavior in this case is undefined and is OS driver
// specific.
//
// It is not required to call Read() to reset the edge detection.
//
// Specify -1 to effectively disable timeout.
WaitForEdge(timeout time.Duration) bool
// Pull returns the internal pull resistor if the pin is set as input pin.
//
// Returns PullNoChange if the value cannot be read.
Pull() Pull
// DefaultPull returns the pull that is initialized on CPU/device reset. This
// is useful to determine if the pin is acceptable for operation with
// certain devices.
DefaultPull() Pull
}
// PinOut is an output GPIO pin.
//
// A LED, a buzzer, a servo, are semantically a PinOut. So if you are looking
// to control these, PinOut is the interface you are looking for.
type PinOut interface {
pin.Pin
// Out sets a pin as output if it wasn't already and sets the initial value.
//
// After the initial call to ensure that the pin has been set as output, it
// is generally safe to ignore the error returned.
//
// Out() tries to empty the accumulated edges detected if the gpio was
// previously set as input but this is not 100% guaranteed due to the OS.
Out(l Level) error
// PWM sets the PWM output on supported pins, if the pin has hardware PWM
// support.
//
// To use as a general purpose clock, set duty to DutyHalf. Some pins may
// only support DutyHalf and no other value.
//
// Using 0 as frequency will use the optimal value as supported/preferred by
// the pin.
//
// To use as a servo, see https://en.wikipedia.org/wiki/Servo_control as an
// explanation how to calculate duty.
PWM(duty Duty, f physic.Frequency) error
}
// PinIO is a GPIO pin that supports both input and output. It matches both
// interfaces PinIn and PinOut.
//
// A GPIO pin implementing PinIO may fail at either input or output or both.
type PinIO interface {
pin.Pin
// PinIn
In(pull Pull, edge Edge) error
Read() Level
WaitForEdge(timeout time.Duration) bool
Pull() Pull
DefaultPull() Pull
// PinOut
Out(l Level) error
PWM(duty Duty, f physic.Frequency) error
}
// INVALID implements PinIO and fails on all access.
var INVALID PinIO
// RealPin is implemented by aliased pin and allows the retrieval of the real
// pin underlying an alias.
//
// Aliases are created by RegisterAlias. Aliases permits presenting a user
// friendly GPIO pin name while representing the underlying real pin.
//
// The purpose of the RealPin is to be able to cleanly test whether an arbitrary
// gpio.PinIO returned by ByName is an alias for another pin, and resolve it.
type RealPin interface {
Real() PinIO // Real returns the real pin behind an Alias
}
//
// errInvalidPin is returned when trying to use INVALID.
var errInvalidPin = errors.New("gpio: invalid pin")
func init() {
INVALID = invalidPin{}
}
// invalidPin implements PinIO for compatibility but fails on all access.
type invalidPin struct {
}
func (invalidPin) String() string {
return "INVALID"
}
func (invalidPin) Halt() error {
return nil
}
func (invalidPin) Number() int {
return -1
}
func (invalidPin) Name() string {
return "INVALID"
}
func (invalidPin) Function() string {
return ""
}
func (invalidPin) Func() pin.Func {
return pin.FuncNone
}
func (invalidPin) SupportedFuncs() []pin.Func {
return nil
}
func (invalidPin) SetFunc(f pin.Func) error {
return errInvalidPin
}
func (invalidPin) In(Pull, Edge) error {
return errInvalidPin
}
func (invalidPin) Read() Level {
return Low
}
func (invalidPin) WaitForEdge(timeout time.Duration) bool {
return false
}
func (invalidPin) Pull() Pull {
return PullNoChange
}
func (invalidPin) DefaultPull() Pull {
return PullNoChange
}
func (invalidPin) Out(Level) error {
return errInvalidPin
}
func (invalidPin) PWM(Duty, physic.Frequency) error {
return errInvalidPin
}
var _ PinIn = INVALID
var _ PinOut = INVALID
var _ PinIO = INVALID
var _ pin.PinFunc = &invalidPin{}
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