mirror of https://github.com/periph/devices
Move code around to make drivers follow a common pattern
The idea is to enable navigating across the code more easily by using similar layout amongs the drivers. Similar to gofmt, it's not about making a stylistic choice, but having a single style. Use the following layout for drivers: - exported support types - Opts struct - New func - Dev struct and methods - Private support code No functional change. A lot of code moved around, so it will likely break any pending PR or fork. :/pull/1/head
Marc-Antoine Ruel
8 years ago
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89531ab87e
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5b5083e8fb
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// Copyright 2016 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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package ds248x
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import (
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"fmt"
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"sync"
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"time"
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"periph.io/x/periph/conn"
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"periph.io/x/periph/conn/onewire"
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)
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// Dev is a handle to a ds248x device and it implements the onewire.Bus
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// interface.
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//
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// Dev implements a persistent error model: if a fatal error is encountered it
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// places itself into an error state and immediately returns the last error on
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// all subsequent calls. A fresh Dev, which reinitializes the hardware, must be
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// created to proceed.
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//
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// A persistent error is only set when there is a problem with the ds248x
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// device itself (or the I²C bus used to access it). Errors on the 1-wire bus
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// do not cause persistent errors and implement the onewire.BusError interface
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// to indicate this fact.
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type Dev struct {
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sync.Mutex // lock for the bus while a transaction is in progress
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i2c conn.Conn // i2c device handle for the ds248x
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isDS2483 bool // true: ds2483, false: ds2482-100
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confReg byte // value written to configuration register
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tReset time.Duration // time to perform a 1-wire reset
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tSlot time.Duration // time to perform a 1-bit 1-wire read/write
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err error // persistent error, device will no longer operate
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}
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func (d *Dev) String() string {
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if d.isDS2483 {
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return fmt.Sprintf("DS2483{%s}", d.i2c)
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}
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return fmt.Sprintf("DS2482-100{%s}", d.i2c)
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}
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// Halt implements conn.Resource.
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func (d *Dev) Halt() error {
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return nil
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}
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// Tx performs a bus transaction, sending and receiving bytes, and ending by
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// pulling the bus high either weakly or strongly depending on the value of
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// power.
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//
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// A strong pull-up is typically required to power temperature conversion or
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// EEPROM writes.
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func (d *Dev) Tx(w, r []byte, power onewire.Pullup) error {
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d.Lock()
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defer d.Unlock()
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// Issue 1-wire bus reset.
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if present, err := d.reset(); err != nil {
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return err
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} else if !present {
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return busError("ds248x: no device present")
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}
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// Send bytes onto 1-wire bus.
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for i, b := range w {
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if power == onewire.StrongPullup && i == len(w)-1 && len(r) == 0 {
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// This is the last byte, need to activate strong pull-up.
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d.i2cTx([]byte{cmdWriteConfig, d.confReg&0xbf | 0x4}, nil)
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}
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d.i2cTx([]byte{cmd1WWrite, b}, nil)
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d.waitIdle(7 * d.tSlot)
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}
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// Read bytes from one-wire bus.
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for i := range r {
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if power == onewire.StrongPullup && i == len(r)-1 {
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// This is the last byte, need to activate strong-pull-up
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d.i2cTx([]byte{cmdWriteConfig, d.confReg&0xbf | 0x4}, nil)
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}
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d.i2cTx([]byte{cmd1WRead}, r[i:i+1])
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d.waitIdle(7 * d.tSlot)
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d.i2cTx([]byte{cmdSetReadPtr, regRDR}, r[i:i+1])
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}
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return d.err
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}
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// Search performs a "search" cycle on the 1-wire bus and returns the addresses
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// of all devices on the bus if alarmOnly is false and of all devices in alarm
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// state if alarmOnly is true.
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//
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// If an error occurs during the search the already-discovered devices are
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// returned with the error.
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func (d *Dev) Search(alarmOnly bool) ([]onewire.Address, error) {
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return onewire.Search(d, alarmOnly)
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}
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// SearchTriplet performs a single bit search triplet command on the bus, waits
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// for it to complete and returs the outcome.
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//
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// SearchTriplet should not be used directly, use Search instead.
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func (d *Dev) SearchTriplet(direction byte) (onewire.TripletResult, error) {
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// Send one-wire triplet command.
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var dir byte
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if direction != 0 {
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dir = 0x80
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}
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d.i2cTx([]byte{cmd1WTriplet, dir}, nil)
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// Wait and read status register, concoct result from there.
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status := d.waitIdle(0 * d.tSlot) // in theory 3*tSlot but it's actually overlapped
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tr := onewire.TripletResult{
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GotZero: status&0x20 == 0,
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GotOne: status&0x40 == 0,
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Taken: status >> 7,
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}
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return tr, d.err
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}
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//
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// reset issues a reset signal on the 1-wire bus and returns true if any device
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// responded with a presence pulse.
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func (d *Dev) reset() (bool, error) {
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// Issue reset.
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d.i2cTx([]byte{cmd1WReset}, nil)
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// Wait for reset to complete.
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status := d.waitIdle(d.tReset)
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if d.err != nil {
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return false, d.err
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}
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// Detect bus short and turn into 1-wire error
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if (status & 4) != 0 {
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return false, shortedBusError("onewire/ds248x: bus has a short")
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}
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return (status & 2) != 0, nil
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}
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// i2cTx is a helper function to call i2c.Tx and handle the error by persisting
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// it.
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func (d *Dev) i2cTx(w, r []byte) {
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if d.err != nil {
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return
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}
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d.err = d.i2c.Tx(w, r)
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}
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// waitIdle waits for the one wire bus to be idle.
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//
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// It initially sleeps for the delay and then polls the status register and
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// sleeps for a tenth of the delay each time the status register indicates that
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// the bus is still busy. The last read status byte is returned.
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//
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// An overall timeout of 3ms is applied to the whole procedure. waitIdle uses
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// the persistent error model and returns 0 if there is an error.
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func (d *Dev) waitIdle(delay time.Duration) byte {
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if d.err != nil {
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return 0
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}
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// Overall timeout.
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tOut := time.Now().Add(3 * time.Millisecond)
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sleep(delay)
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for {
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// Read status register.
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var status [1]byte
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d.i2cTx(nil, status[:])
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// If bus idle complete, return status. This also returns if d.err!=nil
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// because in that case status[0]==0.
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if (status[0] & 1) == 0 {
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return status[0]
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}
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// If we're timing out return error. This is an error with the ds248x, not with
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// devices on the 1-wire bus, hence it is persistent.
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if time.Now().After(tOut) {
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d.err = fmt.Errorf("ds248x: timeout waiting for bus cycle to finish")
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return 0
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}
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// Try not to hog the kernel thread.
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sleep(delay / 10)
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}
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}
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// shortedBusError implements error and onewire.ShortedBusError.
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type shortedBusError string
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func (e shortedBusError) Error() string { return string(e) }
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func (e shortedBusError) IsShorted() bool { return true }
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func (e shortedBusError) BusError() bool { return true }
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// busError implements error and onewire.BusError.
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type busError string
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func (e busError) Error() string { return string(e) }
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func (e busError) BusError() bool { return true }
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var sleep = time.Sleep
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var _ conn.Resource = &Dev{}
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var _ fmt.Stringer = &Dev{}
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