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deadprogram
86 lines
2.8 KiB
Go
86 lines
2.8 KiB
Go
// Package thermistor is for temperature sensing using a thermistor
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// such as the NTC 3950.
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//
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// Datasheet: https://www.farnell.com/datasheets/33552.pdf
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//
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// This code is an interpretation of Adafruit Thermistor module in Python:
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// https://github.com/adafruit/Adafruit_CircuitPython_Thermistor
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//
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// It uses the Steinhart–Hart equation to calculate the temperature
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// based on the resistance:
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// https://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation
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//
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// To use with other thermistors adjust the BCoefficient and NominalTemperature
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// values to match the specific thermistor you wish to use.
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//
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// sensor.NominalTemperature = 25
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// sensor.BCoefficient = 3950
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//
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// Set the SeriesResistor and NominalResistance based on the microcontroller voltage and
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// circuit that you have in use. Set HighSide based on if the thermistor is connected from
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// the ADC pin to the powered side (true) or to ground (false).
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//
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// sensor.SeriesResistor = 10000
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// sensor.NominalResistance = 10000
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// sensor.HighSide = true
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package thermistor // import "tinygo.org/x/drivers/thermistor"
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import (
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"machine"
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"math"
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)
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// Device holds the ADC pin and the needed settings for calculating the
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// temperature based on the resistance.
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type Device struct {
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adc *machine.ADC
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SeriesResistor uint32
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NominalResistance uint32
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NominalTemperature uint32
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BCoefficient uint32
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HighSide bool
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}
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// New returns a new thermistor driver given an ADC pin.
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func New(pin machine.Pin) Device {
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adc := machine.ADC{pin}
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return Device{
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adc: &adc,
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SeriesResistor: 10000,
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NominalResistance: 10000,
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NominalTemperature: 25,
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BCoefficient: 3950,
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HighSide: true,
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}
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}
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// Configure configures the ADC pin used for the thermistor.
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func (d *Device) Configure() {
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d.adc.Configure(machine.ADCConfig{})
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}
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// ReadTemperature returns the temperature in celsius milli degrees (°C/1000)
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func (d *Device) ReadTemperature() (temperature int32, err error) {
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var reading uint32
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if d.HighSide {
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// Thermistor connected from analog input to high logic level.
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val := d.adc.Get()
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reading = uint32(val) / 64
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reading = (1023 * d.SeriesResistor) / reading
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reading -= d.SeriesResistor
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} else {
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// Thermistor connected from analog input to ground.
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reading = d.SeriesResistor / uint32(65535/d.adc.Get()-1)
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}
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var steinhart float64
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steinhart = float64(reading) / float64(d.NominalResistance) // (R/Ro)
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steinhart = math.Log(steinhart) // ln(R/Ro)
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steinhart /= float64(d.BCoefficient) // 1/B * ln(R/Ro)
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steinhart += 1.0 / (float64(d.NominalTemperature) + 273.15) // + (1/To)
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steinhart = 1.0 / steinhart // Invert
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steinhart -= 273.15 // convert to C
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return int32(steinhart * 1000), nil
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}
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