conn

package
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 Go to latest Published: Aug 25, 2017 License: Apache-2.0 Imports: 1 Imported by: 0

Documentation

Overview

Package conn defines core interfaces for protocols and connections.

This package and its subpackages describe the base interfaces to connect the software with the real world. It doesn't contain any implementation but includes registries to enable the application to discover the available hardware.

Concepts

periph uses 3 layered concepts for interfacing: 

Bus → Port → Conn

Not every subpackage expose all 3 concepts. In fact, most packages don't. For example, SPI doesn't expose Bus as the OSes generally only expose the Port, that is, a Chip Select (CS) line must be selected right upfront to get an handle. For I²C, there's no Port to configure, so selecting a "slave" address is sufficient to jump directly from a Bus to a Conn.

periph doesn't have yet a concept of star-like communication network, like an IP network.

Bus

A Bus is a multi-point communication channel where one "master" and multiple "slaves" communicate together. In the case of periph, the Bus handle is assumed to be the "master". The "master" generally initiates communications and selects the "slave" to talk to.

As the "master" selects a "slave" over a bus, a virtual Port is automatically created.

Examples include SPI, I²C and 1-wire. In each case, selecting a communication line (Chip Select (CS) line for SPI, address for I²C or 1-wire) converts the Bus into a Port.

Port

A port is a point-to-point communication channel that is yet to be initialized. It cannot be used for communication until it is connected and transformed into a Conn. Configuring a Port converts it into a Conn. Not all Port need configuration.

Conn

A Conn is a fully configured half or full duplex communication channel that is point-to-point, only between two devices. It is ready to use like any readable and/or writable pipe.

Subpackages

Most connection-type specific subpackages include subpackages:

→ XXXreg: registry as that is populated by the host drivers and that can be leveraged by applications.

→ XXXtest: fake implementation that can be leveraged when writing device driver unit test.

→ XXXsmoketest: smoke test that tests against real hardware to ensure the whole stack work correctly, including the OS supplied drivers.

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Conn 

type Conn interface {
	// Tx does a single transaction.
	//
	// For full duplex protocols (generally SPI, UART), the two buffers must have
	// the same length as both reading and writing happen simultaneously.
	//
	// For half duplex protocols (I²C), there is no restriction as reading
	// happens after writing, and r can be nil.
	//
	// Query Limits.MaxTxSize() to know if there is a limit on the buffer size
	// per Tx() call.
	Tx(w, r []byte) error
	// Duplex returns the current duplex setting for this point-to-point
	// connection.
	//
	// It is expected to be either Half or Full unless the connection itself is
	// in an unknown state.
	Duplex() Duplex
}

Conn defines the interface for a connection on a point-to-point communication channel.

The connection can either be unidirectional (read-only, write-only) or bidirectional (read-write). It can either be half-duplex or full duplex.

This is the lowest common denominator for all point-to-point communication channels.

Implementation are expected but not required to also implement the following interfaces:

- fmt.Stringer which returns something meaningful to the user like "SPI0.1", "I2C1.76", "COM6", etc.

- io.Reader and io.Writer as a way to use io.Copy() for half duplex operation.

- io.Closer for the owner of the communication channel.

Example 
// Get a connection from one of the registries, for example:
//   b, _ := spireg.Open("SPI0.0")
//   c, _ := b.DevParams(1000000, spi.Mode3, 8)
var c Conn

// Send a command over the connection without reading.
cmd := []byte("command")
if err := c.Tx(cmd, nil); err != nil {
	log.Fatal(err)
}

Output:

type Duplex 

type Duplex int

Duplex declares whether communication can happen simultaneously both ways.

Some protocol can be either depending on configuration settings, like UART. 

const (
	// DuplexUnknown is used when the duplex of a connection is yet to be known.
	//
	// Some protocol can be configured either as half-duplex or full-duplex and
	// the connection is not yet is a determinate state.
	DuplexUnknown Duplex = 0
	// Half means that communication can only occurs one way at a time.
	//
	// Examples include 1-wire and I²C.
	Half Duplex = 1
	// Full means that communication occurs simultaneously both ways in a
	// synchronized manner.
	//
	// Examples include SPI (except 3-wire variant).
	Full Duplex = 2
)

func (Duplex) String 

func (i Duplex) String() string

type Limits 

type Limits interface {
	// MaxTxSize returns the maximum allowed data size to be sent as a single
	// I/O.
	//
	// Returns 0 if undefined.
	MaxTxSize() int
}

Limits returns information about the connection's limits.

Source Files

View all Source files

Directories

Path Synopsis
Package conntest implements fakes for package conn.
 Package conntest implements fakes for package conn.
Package gpio defines digital pins.
 Package gpio defines digital pins.
gpioreg
Package gpioreg defines a registry for the known digital pins.
 Package gpioreg defines a registry for the known digital pins.
gpiosmoketest
Package gpiosmoketest is leveraged by periph-smoketest to verify that basic GPIO pin functionality work.
 Package gpiosmoketest is leveraged by periph-smoketest to verify that basic GPIO pin functionality work.
gpiostream
Package gpiostream defines digital streams.
 Package gpiostream defines digital streams.
gpiotest
Package gpiotest is meant to be used to test drivers using fake Pins.
 Package gpiotest is meant to be used to test drivers using fake Pins.
i2c
Package i2c defines interface to an I²C bus and an I²C device.
 Package i2c defines interface to an I²C bus and an I²C device.
i2creg
Package i2creg defines I²C bus registry to list buses present on the host.
 Package i2creg defines I²C bus registry to list buses present on the host.
i2csmoketest
Package i2csmoketest is leveraged by periph-smoketest to verify that an I²C EEPROM device and a DS2483 device can be accessed on an I²C bus.
 Package i2csmoketest is leveraged by periph-smoketest to verify that an I²C EEPROM device and a DS2483 device can be accessed on an I²C bus.
i2ctest
Package i2ctest is meant to be used to test drivers over a fake I²C bus.
 Package i2ctest is meant to be used to test drivers over a fake I²C bus.
Package ir defines InfraRed codes for use with a IR remote control.
 Package ir defines InfraRed codes for use with a IR remote control.
Package mmr defines helpers to interact with devices exposing Memory Mapped Registers protocol.
 Package mmr defines helpers to interact with devices exposing Memory Mapped Registers protocol.
Package onewire defines a Dallas Semiconductor / Maxim Integrated 1-wire bus.
 Package onewire defines a Dallas Semiconductor / Maxim Integrated 1-wire bus.
onewirereg
Package onewirereg defines a registry for onewire buses present on the host.
 Package onewirereg defines a registry for onewire buses present on the host.
onewiresmoketest
Package onewiresmoketest is leveraged by periph-smoketest to verify that a 1-wire bus search returns two devices, that a ds18b20 temperature sensor can be read, and that a ds2431 eeprom can be written and read.
 Package onewiresmoketest is leveraged by periph-smoketest to verify that a 1-wire bus search returns two devices, that a ds18b20 temperature sensor can be read, and that a ds2431 eeprom can be written and read.
onewiretest
Package onewiretest is meant to be used to test drivers over a fake 1-wire bus.
 Package onewiretest is meant to be used to test drivers over a fake 1-wire bus.
pin
Package pin declare well known pins.
 Package pin declare well known pins.
pinreg
Package pinreg is a registry for the physical headers (made up of pins) on a host.
 Package pinreg is a registry for the physical headers (made up of pins) on a host.
spi
Package spi defines the SPI protocol.
 Package spi defines the SPI protocol.
spireg
Package spireg defines the SPI registry for SPI ports discovered on the host.
 Package spireg defines the SPI registry for SPI ports discovered on the host.
spismoketest
Package spismoketest is leveraged by periph-smoketest to verify that an EEPROM device can be accessed on a SPI port.
 Package spismoketest is leveraged by periph-smoketest to verify that an EEPROM device can be accessed on a SPI port.
spitest
Package spitest is meant to be used to test drivers over a fake SPI port.
 Package spitest is meant to be used to test drivers over a fake SPI port.

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