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vendor/periph.io/x/conn/v3/gpio/gpio.go

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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/conn/v3/physic"
+	"periph.io/x/conn/v3/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{}