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251 lines
6.4 KiB
Go
251 lines
6.4 KiB
Go
// Copyright 2016 The PIO 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 bme280
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import (
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"fmt"
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"log"
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"testing"
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"github.com/google/pio/conn/i2c"
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"github.com/google/pio/conn/i2c/i2ctest"
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"github.com/google/pio/devices"
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)
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// Real data extracted from a device.
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var calib = calibration{
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t1: 28176,
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t2: 26220,
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t3: 350,
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p1: 38237,
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p2: -10824,
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p3: 3024,
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p4: 7799,
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p5: -99,
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p6: -7,
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p7: 9900,
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p8: -10230,
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p9: 4285,
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h2: 366, // Note they are inversed for bit packing.
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h1: 75,
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h3: 0,
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h4: 309,
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h5: 0,
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h6: 30,
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}
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func TestRead(t *testing.T) {
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// This data was generated with "bme280 -r"
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bus := i2ctest.Playback{
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Ops: []i2ctest.IO{
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// Chipd ID detection.
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{Addr: 0x76, Write: []byte{0xd0}, Read: []byte{0x60}},
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// Calibration data.
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{
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Addr: 0x76,
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Write: []byte{0x88},
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Read: []byte{0x10, 0x6e, 0x6c, 0x66, 0x32, 0x0, 0x5d, 0x95, 0xb8, 0xd5, 0xd0, 0xb, 0x77, 0x1e, 0x9d, 0xff, 0xf9, 0xff, 0xac, 0x26, 0xa, 0xd8, 0xbd, 0x10, 0x0, 0x4b},
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},
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// Calibration data.
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{Addr: 0x76, Write: []byte{0xe1}, Read: []byte{0x6e, 0x1, 0x0, 0x13, 0x5, 0x0, 0x1e}},
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// Configuration.
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{Addr: 0x76, Write: []byte{0xf4, 0x6c, 0xf2, 0x3, 0xf5, 0xe0, 0xf4, 0x6f}, Read: nil},
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// Read.
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{Addr: 0x76, Write: []byte{0xf7}, Read: []byte{0x4a, 0x52, 0xc0, 0x80, 0x96, 0xc0, 0x7a, 0x76}},
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},
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}
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dev, err := NewI2C(&bus, nil)
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if err != nil {
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t.Fatal(err)
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}
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env := devices.Environment{}
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if err := dev.Sense(&env); err != nil {
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t.Fatalf("Sense(): %v", err)
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}
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if env.Temperature != 23720 {
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t.Fatalf("temp %d", env.Temperature)
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}
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if env.Pressure != 100943 {
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t.Fatalf("pressure %d", env.Pressure)
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}
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if env.Humidity != 6531 {
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t.Fatalf("humidity %d", env.Humidity)
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}
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}
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func TestCalibrationFloat(t *testing.T) {
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// Real data extracted from measurements from this device.
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tRaw := int32(524112)
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pRaw := int32(309104)
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hRaw := int32(30987)
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// Compare the values with the 3 algorithms.
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temp, tFine := calib.compensateTempFloat(tRaw)
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pres := calib.compensatePressureFloat(pRaw, tFine)
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humi := calib.compensateHumidityFloat(hRaw, tFine)
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if tFine != 117494 {
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t.Fatalf("tFine %d", tFine)
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}
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if !floatEqual(temp, 22.948120) {
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// 22.95°C
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t.Fatalf("temp %f", temp)
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}
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if !floatEqual(pres, 100.046074) {
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// 100.046kPa
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t.Fatalf("pressure %f", pres)
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}
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if !floatEqual(humi, 63.167889) {
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// 63.17%
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t.Fatalf("humidity %f", humi)
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}
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}
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func TestCalibrationInt(t *testing.T) {
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// Real data extracted from measurements from this device.
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tRaw := int32(524112)
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pRaw := int32(309104)
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hRaw := int32(30987)
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temp, tFine := calib.compensateTempInt(tRaw)
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pres64 := calib.compensatePressureInt64(pRaw, tFine)
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pres32 := calib.compensatePressureInt32(pRaw, tFine)
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humi := calib.compensateHumidityInt(hRaw, tFine)
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if tFine != 117407 {
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t.Fatalf("tFine %d", tFine)
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}
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if temp != 2293 {
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// 2293/100 = 22.93°C
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// Delta is <0.02°C which is pretty good.
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t.Fatalf("temp %d", temp)
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}
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if pres64 != 25611063 {
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// 25611063/256/1000 = 100.043214844
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// Delta is 3Pa which is ok.
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t.Fatalf("pressure64 %d", pres64)
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}
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if pres32 != 100045 {
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// 100045/1000 = 100.045kPa
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// Delta is 1Pa which is pretty good.
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t.Fatalf("pressure32 %d", pres32)
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}
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if humi != 64686 {
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// 64686/1024 = 63.17%
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// Delta is <0.01% which is pretty good.
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t.Fatalf("humidity %d", humi)
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}
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}
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//
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func Example() {
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bus, err := i2c.New(-1)
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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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dev, err := NewI2C(bus, nil)
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if err != nil {
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log.Fatalf("failed to initialize bme280: %v", err)
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}
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env := devices.Environment{}
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if err := dev.Sense(&env); err != nil {
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log.Fatal(err)
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}
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fmt.Printf("%8s %10s %9s\n", env.Temperature, env.Pressure, env.Humidity)
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}
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//
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var epsilon float32 = 0.00000001
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func floatEqual(a, b float32) bool {
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return (a-b) < epsilon && (b-a) < epsilon
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}
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// Page 50
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// compensatePressureInt32 returns pressure in Pa. Output value of "96386"
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// equals 96386 Pa = 963.86 hPa
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//
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// "Compensating the pressure value with 32 bit integer has an accuracy of
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// typically 1 Pa"
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//
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// raw has 20 bits of resolution.
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//
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// BUG(maruel): Output is incorrect.
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func (c *calibration) compensatePressureInt32(raw, tFine int32) uint32 {
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x := tFine>>1 - 64000
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y := (((x >> 2) * (x >> 2)) >> 11) * int32(c.p6)
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y += (x * int32(c.p5)) << 1
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y = y>>2 + int32(c.p4)<<16
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x = (((int32(c.p3) * (((x >> 2) * (x >> 2)) >> 13)) >> 3) + ((int32(c.p2) * x) >> 1)) >> 18
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x = ((32768 + x) * int32(c.p1)) >> 15
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if x == 0 {
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return 0
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}
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p := ((uint32(int32(1048576)-raw) - uint32(y>>12)) * 3125)
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if p < 0x80000000 {
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p = (p << 1) / uint32(x)
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} else {
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p = (p / uint32(x)) * 2
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}
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x = (int32(c.p9) * int32(((p>>3)*(p>>3))>>13)) >> 12
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y = (int32(p>>2) * int32(c.p8)) >> 13
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return uint32(int32(p) + ((x + y + int32(c.p7)) >> 4))
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}
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var _ devices.Environmental = &Dev{}
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// Page 49
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// compensateTempFloat returns temperature in °C. Output value of "51.23"
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// equals 51.23 °C.
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//
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// raw has 20 bits of resolution.
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func (c *calibration) compensateTempFloat(raw int32) (float32, int32) {
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x := (float64(raw)/16384. - float64(c.t1)/1024.) * float64(c.t2)
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y := (float64(raw)/131072. - float64(c.t1)/8192.) * float64(c.t3)
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tFine := int32(x + y)
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return float32((x + y) / 5120.), tFine
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}
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// compensateHumidityFloat returns pressure in Pa. Output value of "96386.2"
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// equals 96386.2 Pa = 963.862 hPa.
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//
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// raw has 20 bits of resolution.
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func (c *calibration) compensatePressureFloat(raw, tFine int32) float32 {
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x := float64(tFine)*0.5 - 64000.
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y := x * x * float64(c.p6) / 32768.
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y += x * float64(c.p5) * 2.
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y = y*0.25 + float64(c.p4)*65536.
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x = (float64(c.p3)*x*x/524288. + float64(c.p2)*x) / 524288.
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x = (1. + x/32768.) * float64(c.p1)
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if x <= 0 {
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return 0
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}
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p := float64(1048576 - raw)
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p = (p - y/4096.) * 6250. / x
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x = float64(c.p9) * p * p / 2147483648.
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y = p * float64(c.p8) / 32768.
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return float32(p+(x+y+float64(c.p7))/16.) / 1000.
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}
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// compensateHumidityFloat returns humidity in %rH. Output value of "46.332"
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// represents 46.332 %rH.
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//
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// raw has 16 bits of resolution.
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func (c *calibration) compensateHumidityFloat(raw, tFine int32) float32 {
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h := float64(tFine - 76800)
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h = (float64(raw) - float64(c.h4)*64. + float64(c.h5)/16384.*h) * float64(c.h2) / 65536. * (1. + float64(c.h6)/67108864.*h*(1.+float64(c.h3)/67108864.*h))
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h *= 1. - float64(c.h1)*h/524288.
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if h > 100. {
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return 100.
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}
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if h < 0. {
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return 0.
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}
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return float32(h)
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}
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