did something

vendor/periph.io/x/conn/v3/i2c/i2c.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 i2c defines the API to communicate with devices over the I²C
+// protocol.
+//
+// As described in https://periph.io/x/conn/v3#hdr-Concepts, periph.io uses
+// the concepts of Bus, Port and Conn.
+//
+// In the package i2c, 'Port' is not exposed, since once you know the I²C
+// device address, there's no unconfigured Port to configure.
+//
+// Instead, the package includes the adapter 'Dev' to directly convert an I²C
+// bus 'i2c.Bus' into a connection 'conn.Conn' by only specifying the device
+// I²C address.
+//
+// See https://en.wikipedia.org/wiki/I%C2%B2C for more information.
+package i2c
+
+import (
+	"errors"
+	"io"
+	"strconv"
+
+	"periph.io/x/conn/v3"
+	"periph.io/x/conn/v3/gpio"
+	"periph.io/x/conn/v3/physic"
+)
+
+// Bus defines the interface a concrete I²C driver must implement.
+//
+// This interface is consummed by a device driver for a device sitting on a bus.
+//
+// This interface doesn't implement conn.Conn since a device address must be
+// specified. Use i2cdev.Dev as an adapter to get a conn.Conn compatible
+// object.
+type Bus interface {
+	String() string
+	// Tx does a transaction at the specified device address.
+	//
+	// Write is done first, then read. One of 'w' or 'r' can be omitted for a
+	// unidirectional operation.
+	Tx(addr uint16, w, r []byte) error
+	// SetSpeed changes the bus speed, if supported.
+	//
+	// On linux due to the way the I²C sysfs driver is exposed in userland,
+	// calling this function will likely affect *all* I²C buses on the host.
+	SetSpeed(f physic.Frequency) error
+}
+
+// BusCloser is an I²C bus that can be closed.
+//
+// This interface is meant to be handled by the application and not the device
+// driver. A device driver doesn't "own" a bus, hence it must operate on a Bus,
+// not a BusCloser.
+type BusCloser interface {
+	io.Closer
+	Bus
+}
+
+// Pins defines the pins that an I²C bus interconnect is using on the host.
+//
+// It is expected that a implementer of Bus also implement Pins but this is not
+// a requirement.
+type Pins interface {
+	// SCL returns the CLK (clock) pin.
+	SCL() gpio.PinIO
+	// SDA returns the DATA pin.
+	SDA() gpio.PinIO
+}
+
+// Dev is a device on a I²C bus.
+//
+// It implements conn.Conn.
+//
+// It saves from repeatedly specifying the device address.
+type Dev struct {
+	Bus  Bus
+	Addr uint16
+}
+
+func (d *Dev) String() string {
+	s := "<nil>"
+	if d.Bus != nil {
+		s = d.Bus.String()
+	}
+	return s + "(" + strconv.Itoa(int(d.Addr)) + ")"
+}
+
+// Tx does a transaction by adding the device's address to each command.
+//
+// It's a wrapper for Bus.Tx().
+func (d *Dev) Tx(w, r []byte) error {
+	return d.Bus.Tx(d.Addr, w, r)
+}
+
+// Write writes to the I²C bus without reading, implementing io.Writer.
+//
+// It's a wrapper for Tx()
+func (d *Dev) Write(b []byte) (int, error) {
+	if err := d.Tx(b, nil); err != nil {
+		return 0, err
+	}
+	return len(b), nil
+}
+
+// Duplex always return conn.Half for I²C.
+func (d *Dev) Duplex() conn.Duplex {
+	return conn.Half
+}
+
+// Addr is an I²C slave address.
+type Addr uint16
+
+// Set sets the Addr to a value represented by the string s. Values maybe in
+// decimal or hexadecimal form. Set implements the flag.Value interface.
+func (a *Addr) Set(s string) error {
+	// Allow for only maximum of 10 bits for i2c addresses.
+	u, err := strconv.ParseUint(s, 0, 10)
+	if err != nil {
+		return errI2CSetError
+	}
+	*a = Addr(u)
+	return nil
+}
+
+// String returns an i2c.Addr as a string formated in hexadecimal.
+func (a Addr) String() string {
+	return "0x" + strconv.FormatInt(int64(a), 16)
+}
+
+var errI2CSetError = errors.New("invalid i2c address")
+
+var _ conn.Conn = &Dev{}