physic: Add Precision to SenseEnv

Implement for bme280 and sysfs

devices/bmxx80/bmp180_test.go

@@ -332,6 +332,39 @@ func TestSenseContinuous180_success(t *testing.T) {
 	}
 }
 
+func TestBmp180Precision(t *testing.T) {
+	bus := i2ctest.Playback{
+		Ops: []i2ctest.IO{
+			// Chip ID detection.
+			{Addr: 0x77, W: []byte{0xd0}, R: []byte{0x55}},
+			// Calibration data.
+			{
+				Addr: 0x77,
+				W:    []byte{0xaa},
+				R:    []byte{35, 136, 251, 103, 199, 169, 135, 91, 98, 137, 80, 22, 25, 115, 0, 46, 128, 0, 209, 246, 10, 123},
+			},
+		},
+	}
+	dev, err := NewI2C(&bus, 0x77, &DefaultOpts)
+	if err != nil {
+		t.Fatal(err)
+	}
+	e := physic.Env{}
+	dev.Precision(&e)
+	if e.Temperature != 100*physic.MilliKelvin {
+		t.Fatal(e.Temperature)
+	}
+	if e.Pressure != physic.Pascal {
+		t.Fatal(e.Pressure)
+	}
+	if e.Humidity != 0 {
+		t.Fatal(e.Humidity)
+	}
+	if err := bus.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
 /*
 func TestOversampling(t *testing.T) {
 	data := []struct {

devices/bmxx80/bmx280_test.go

@@ -734,6 +734,43 @@ func TestCalibration280_limits_419430400(t *testing.T) {
 	// TODO(maruel): Reverse the equation to overflow  419430400
 }
 
+func TestBme280Precision(t *testing.T) {
+	bus := i2ctest.Playback{
+		Ops: []i2ctest.IO{
+			// Chip ID detection.
+			{Addr: 0x76, W: []byte{0xd0}, R: []byte{0x60}},
+			// Calibration data.
+			{
+				Addr: 0x76,
+				W:    []byte{0x88},
+				R:    []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},
+			},
+			// Calibration data humidity.
+			{Addr: 0x76, W: []byte{0xe1}, R: []byte{0x6e, 0x1, 0x0, 0x13, 0x5, 0x0, 0x1e}},
+			// Configuration.
+			{Addr: 0x76, W: []byte{0xf4, 0x6c, 0xf2, 0x3, 0xf5, 0xa0, 0xf4, 0x6c}, R: nil},
+		},
+	}
+	dev, err := NewI2C(&bus, 0x76, &DefaultOpts)
+	if err != nil {
+		t.Fatal(err)
+	}
+	e := physic.Env{}
+	dev.Precision(&e)
+	if e.Temperature != 10*physic.MilliKelvin {
+		t.Fatal(e.Temperature)
+	}
+	if e.Pressure != 15625*physic.MicroPascal/4 {
+		t.Fatal(e.Pressure)
+	}
+	if e.Humidity != physic.MicroRH*1000/1024 {
+		t.Fatal(int(e.Humidity))
+	}
+	if err := bus.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
 //
 
 func TestOversampling(t *testing.T) {

devices/bmxx80/bmxx80.go

@@ -8,6 +8,7 @@
 // BMx280
 //
 // https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME280_DS001-11.pdf
+// https://www.mouser.com/datasheet/2/783/BST-BME280_DS001-11-844833.pdf
 //
 // https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BMP280-DS001-18.pdf
 //
@@ -320,6 +321,21 @@ func (d *Dev) SenseContinuous(interval time.Duration) (<-chan physic.Env, error)
 	return sensing, nil
 }
 
+// Precision implements physic.SenseEnv.
+func (d *Dev) Precision(e *physic.Env) {
+	if d.is280 {
+		e.Temperature = 10 * physic.MilliKelvin
+		e.Pressure = 15625 * physic.MicroPascal / 4
+	} else {
+		e.Temperature = 100 * physic.MilliKelvin
+		e.Pressure = physic.Pascal
+	}
+
+	if d.isBME {
+		e.Humidity = physic.MicroRH * 1000 / 1024
+	}
+}
+
 // Halt stops the BMxx80 from acquiring measurements as initiated by
 // SenseContinuous().
 //