max31865

README

mikesmitty/max31865

This is a library for using the MAX31865 PT100/PT1000 RTD temperature sensor amplifier in Go using Periph. Originally based on the vemo-france/max31865 port of Adafruit's MAX31865 library, though it has been fairly substantially rewritten. Intended for use with Adafruit's MAX31865 breakout boards PT100/PT1000 on any device supported by Periph.

Installation

go get github.com/mikesmitty/max31865

Usage

package main

import (
	"fmt"

	"github.com/mikesmitty/max31865"
	"periph.io/x/conn/v3/spi/spireg"
	"periph.io/x/host/v3"
)

func main() {
	sb, _ := spireg.Open(yourSpiBus)
	dev, _ := max31865.New(sb, max31865.AdafruitPT100())

	// Perform a one-off reading with Sense()
	var e physic.Env
	_ := dev.Sense(&e)
	fmt.Printf("Temperature: %0.2f\n", e.Temperature.Celsius())

	// Alternatively, SenseContinuous() returns a channel for continuous updates
	c, _ := dev.SenseContinuous(updateInterval)
	for {
		e := <-c
		fmt.Printf("Temperature: %0.2f\n", e.Temperature.Celsius())
	}
}

TODO

• Improve documentation
• Add tests
• Surface hardware fault error codes rather than just clearing them like the Adafruit library does

Documentation

Index

• type Dev
  • func New(p spi.Port, opts *Opts) (*Dev, error)
  • func (d *Dev) CheckError() error
  • func (d *Dev) Halt() error
  • func (d *Dev) Precision(e *physic.Env)
  • func (d *Dev) Sense(e *physic.Env) error
  • func (d *Dev) SenseContinuous(interval time.Duration) (<-chan physic.Env, error)
  • func (d *Dev) SetThreshold(lower, upper uint16) error
  • func (d *Dev) String() string
• type Opts
  • func AdafruitPT100() *Opts
  • func AdafruitPT1000() *Opts
  • func DefaultOptions() *Opts
• type RTDType
• type WireCount

Types

type Dev

type Dev struct {
	// contains filtered or unexported fields
}

func New

func New(p spi.Port, opts *Opts) (*Dev, error)

func (*Dev) CheckError

func (d *Dev) CheckError() error

func (*Dev) Halt

func (d *Dev) Halt() error

Halt stops the MAX31865 from acquiring measurements as initiated by SenseContinuous().

It is recommended to call this function before terminating the process to reduce idle power usage and a goroutine leak.

func (*Dev) Precision

func (d *Dev) Precision(e *physic.Env)

15-Bit ADC Resolution; Nominal temperature resolution varies due to RTD non-linearity

func (*Dev) Sense

func (d *Dev) Sense(e *physic.Env) error

func (*Dev) SenseContinuous

func (d *Dev) SenseContinuous(interval time.Duration) (<-chan physic.Env, error)

SenseContinuous returns measurements as °C on a continuous basis.

The application must call Halt() to stop the sensing when done to stop the sensor and close the channel.

It's the responsibility of the caller to retrieve the values from the channel as fast as possible, otherwise the interval may not be respected.

func (*Dev) SetThreshold

func (d *Dev) SetThreshold(lower, upper uint16) error

func (*Dev) String

func (d *Dev) String() string

type Opts

type Opts struct {
	// ContinuousMode removes delays by leaving the bias voltage enabled between
	// readings. This slightly increases power consumption and self-heating, but
	// is useful when taking measurements as quickly as possible (< 55/66ms)
	ContinuousMode bool
	// 60Hz noise is filtered by default, enable to filter 50Hz noise instead.
	Filter50Hz  bool
	Port        string
	RefResistor float64
	RTDType     RTDType
	WireCount   WireCount
}

Opts holds various configuration options for the sensor

func AdafruitPT100

func AdafruitPT100() *Opts

func AdafruitPT1000

func AdafruitPT1000() *Opts

func DefaultOptions

func DefaultOptions() *Opts

type RTDType

type RTDType int

const (
	RTDPT100 RTDType = iota
	RTDPT1000
)

type WireCount

type WireCount int

const (
	WireCount2 WireCount = iota + 2
	WireCount3
	WireCount4
)