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NeuralSpazmaruel
NeuralSpaz
authored and
maruel
committed
ina219: add i2c driver for high side current and voltage sensor (#292)
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‎experimental/cmd/ina219/main.go‎

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// Copyright 2018 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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// ina219 communicates with an ina219 sensor reading voltage, current and power.
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package main
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import (
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"flag"
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"fmt"
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"os"
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"os/signal"
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"syscall"
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"time"
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"periph.io/x/periph/conn/i2c/i2creg"
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"periph.io/x/periph/experimental/devices/ina219"
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"periph.io/x/periph/host"
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)
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func mainImpl() error {
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if _, err := host.Init(); err != nil {
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return err
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}
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address := flag.Int("address", 0x40, "I²C address")
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i2cbus := flag.String("bus", "", "I²C bus (/dev/i2c-1)")
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flag.Parse()
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fmt.Println("Starting INA219 Current Sensor")
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if _, err := host.Init(); err != nil {
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return err
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}
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// Open default I²C bus.
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bus, err := i2creg.Open(*i2cbus)
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if err != nil {
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return fmt.Errorf("failed to open I²C: %v", err)
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}
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defer bus.Close()
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// Create a new power sensor a sense with default options of 100 mΩ, 3.2A at
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// address of 0x40 if no other address supplied with command line option.
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sensor, err := ina219.New(bus, &ina219.Opts{Address: *address})
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if err != nil {
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return fmt.Errorf("failed to open new sensor: %v", err)
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}
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// Read values from sensor every second.
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everySecond := time.NewTicker(time.Second).C
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var halt = make(chan os.Signal)
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signal.Notify(halt, syscall.SIGTERM)
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signal.Notify(halt, syscall.SIGINT)
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fmt.Println("ctrl+c to exit")
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for {
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select {
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case <-everySecond:
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p, err := sensor.Sense()
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if err != nil {
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return fmt.Errorf("sensor reading error: %v", err)
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}
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fmt.Println(p)
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case <-halt:
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return nil
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}
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}
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}
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func main() {
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if err := mainImpl(); err != nil {
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fmt.Fprintf(os.Stderr, "ina219: %s.\n", err)
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return
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}
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}

‎experimental/devices/ina219/doc.go‎

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// Copyright 2018 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 ina219 controls a Texas Instruments ina219 high side current,
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// voltage and power monitor IC over an i2c bus.
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//
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// Calibration
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//
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// Calibration is recommended for accurate current and power measurements.
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// Voltage measurements do not require sensor calibration. To calibrate meansure
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// the actual value of the shunt resistor.
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//
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// Datasheet
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//
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// http://www.ti.com/lit/ds/symlink/ina219.pdf
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package ina219

‎experimental/devices/ina219/example_test.go‎

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// Copyright 2018 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 ina219_test
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import (
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"fmt"
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"log"
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"periph.io/x/periph/conn/i2c/i2creg"
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"periph.io/x/periph/experimental/devices/ina219"
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"periph.io/x/periph/host"
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)
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func Example() {
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// Make sure periph is initialized.
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if _, err := host.Init(); err != nil {
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log.Fatal(err)
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}
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// Open default I²C bus.
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bus, err := i2creg.Open("")
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if err != nil {
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log.Fatalf("failed to open I²C: %v", err)
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}
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defer bus.Close()
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// Create a new power sensor.
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sensor, err := ina219.New(bus, &ina219.DefaultOpts)
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if err != nil {
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log.Fatalln(err)
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}
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// Read values from sensor.
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measurement, err := sensor.Sense()
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if err != nil {
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log.Fatalln(err)
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}
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fmt.Println(measurement)
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}

‎experimental/devices/ina219/ina219.go‎

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// Copyright 2018 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 ina219
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"sync"
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"periph.io/x/periph/conn/i2c"
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"periph.io/x/periph/conn/mmr"
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"periph.io/x/periph/conn/physic"
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)
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// Opts holds the configuration options.
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//
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// Slave Address
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//
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// Depending which pins the A1, A0 pins are connected to will change the slave
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// address. Default configuration is address 0x40 (both pins to GND). For a full
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// address table see datasheet.
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type Opts struct {
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Address int
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SenseResistor physic.ElectricResistance
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MaxCurrent physic.ElectricCurrent
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}
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// DefaultOpts is the recommended default options.
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var DefaultOpts = Opts{
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Address: 0x40,
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SenseResistor: 100 * physic.MilliOhm,
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MaxCurrent: 3200 * physic.MilliAmpere,
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}
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// New opens a handle to an ina219 sensor.
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func New(bus i2c.Bus, opts *Opts) (*Dev, error) {
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i2cAddress := DefaultOpts.Address
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if opts.Address != 0 {
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if opts.Address < 0x40 || opts.Address > 0x4f {
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return nil, errAddressOutOfRange
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}
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i2cAddress = opts.Address
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}
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senseResistor := DefaultOpts.SenseResistor
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if opts.SenseResistor != 0 {
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if opts.SenseResistor < 1 {
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return nil, errSenseResistorValueInvalid
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}
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senseResistor = opts.SenseResistor
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}
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maxCurrent := DefaultOpts.MaxCurrent
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if opts.MaxCurrent != 0 {
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if opts.MaxCurrent < 1 {
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return nil, errMaxCurrentInvalid
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}
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maxCurrent = opts.MaxCurrent
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}
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dev := &Dev{
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m: mmr.Dev8{
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Conn: &i2c.Dev{Bus: bus, Addr: uint16(i2cAddress)},
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Order: binary.BigEndian,
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},
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}
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if err := dev.calibrate(senseResistor, maxCurrent); err != nil {
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return nil, err
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}
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if err := dev.m.WriteUint16(configRegister, 0x1FFF); err != nil {
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return nil, errWritingToConfigRegister
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}
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return dev, nil
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}
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// Dev is a handle to the ina219 sensor.
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type Dev struct {
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m mmr.Dev8
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mu sync.Mutex
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currentLSB physic.ElectricCurrent
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powerLSB physic.Power
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}
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const (
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configRegister = 0x00
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shuntVoltageRegister = 0x01
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busVoltageRegister = 0x02
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powerRegister = 0x03
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currentRegister = 0x04
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calibrationRegister = 0x05
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)
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// Sense reads the power values from the ina219 sensor.
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func (d *Dev) Sense() (PowerMonitor, error) {
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d.mu.Lock()
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defer d.mu.Unlock()
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var pm PowerMonitor
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shunt, err := d.m.ReadUint16(shuntVoltageRegister)
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if err != nil {
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return PowerMonitor{}, errReadShunt
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}
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// Least significant bit is 10µV.
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pm.Shunt = physic.ElectricPotential(shunt) * 10 * physic.MicroVolt
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bus, err := d.m.ReadUint16(busVoltageRegister)
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if err != nil {
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return PowerMonitor{}, errReadBus
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}
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// Check if bit zero is set, if set the ADC has overflowed.
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if bus&1 > 0 {
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return PowerMonitor{}, errRegisterOverflow
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}
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// Least significant bit is 4mV.
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pm.Voltage = physic.ElectricPotential(bus>>3) * 4 * physic.MilliVolt
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current, err := d.m.ReadUint16(currentRegister)
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if err != nil {
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return PowerMonitor{}, errReadCurrent
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}
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pm.Current = physic.ElectricCurrent(current) * d.currentLSB
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power, err := d.m.ReadUint16(powerRegister)
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if err != nil {
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return PowerMonitor{}, errReadPower
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}
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pm.Power = physic.Power(power) * d.powerLSB
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return pm, nil
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}
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// Since physic electrical is in nano units we need to scale taking care to not
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// overflow int64 or loose resolution.
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const calibratescale int64 = ((int64(physic.Ampere) * int64(physic.Ohm)) / 100000) << 12
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// calibrate sets the scaling factor of the current and power registers for the
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// maximum resolution. calibrate is run on init.
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func (d *Dev) calibrate(sense physic.ElectricResistance, maxCurrent physic.ElectricCurrent) error {
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// TODO: Check calibration with float implementation in tests.
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if sense <= 0 {
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return errSenseResistorValueInvalid
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}
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if maxCurrent <= 0 {
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return errMaxCurrentInvalid
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}
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d.mu.Lock()
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defer d.mu.Unlock()
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d.currentLSB = maxCurrent / (2 << 15)
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d.powerLSB = physic.Power(d.currentLSB * 20)
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// Calibration Register = 0.04096 / (current LSB * Shunt Resistance)
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// Where lsb is in Amps and resistance is in ohms.
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// Calibration register is 16 bits.
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cal := uint16(calibratescale / (int64(d.currentLSB) * int64(sense)))
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return d.m.WriteUint16(calibrationRegister, cal)
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}
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// PowerMonitor represents measurements from ina219 sensor.
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type PowerMonitor struct {
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Shunt physic.ElectricPotential
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Voltage physic.ElectricPotential
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Current physic.ElectricCurrent
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Power physic.Power
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}
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// String returns a PowerMonitor as string
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func (p PowerMonitor) String() string {
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return fmt.Sprintf("Bus: %s, Current: %s, Power: %s, Shunt: %s", p.Voltage, p.Current, p.Power, p.Shunt)
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}
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var (
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errReadShunt = errors.New("failed to read shunt voltage")
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errReadBus = errors.New("failed to read bus voltage")
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errReadPower = errors.New("failed to read power")
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errReadCurrent = errors.New("failed to read current")
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errAddressOutOfRange = errors.New("i2c address out of range")
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errSenseResistorValueInvalid = errors.New("sense resistor value cannot be negative or zero")
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errMaxCurrentInvalid = errors.New("max current cannot be negative or zero")
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errRegisterOverflow = errors.New("bus voltage register overflow")
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errWritingToConfigRegister = errors.New("failed to write to configuration register")
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)

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