Fix temperature offset to be of type f32, closes #11

.travis.yml

@@ -5,7 +5,7 @@ rust:
   - nightly
 script:
   - cargo build --verbose
-  - cargo test --verbose --no-run
+  - cargo test --verbose
 matrix:
   allow_failures:
     - rust: nightly

examples/reading_temperature.rs

@@ -30,6 +30,7 @@ fn main(
         .with_temperature_oversampling(OversamplingSetting::OS8x)
         .with_temperature_filter(IIRFilterSize::Size3)
         .with_gas_measurement(Duration::from_millis(1500), 320, 25)
+        .with_temperature_offset(-2.2)
         .with_run_gas(true)
         .build();
 

src/calc.rs

@@ -46,16 +46,17 @@ impl Calc {
     /// * `temp_adc`
     /// * `temp_offset` - If set, the temperature t_fine will be increased by given
     ///                   value in celsius. Temperature offset in Celsius, e.g. 4, -8, 1.25
-    pub fn calc_temperature(calib: &CalibData, temp_adc: u32, temp_offset: Option<i32>) -> (i16, i32) {
+    pub fn calc_temperature(calib: &CalibData, temp_adc: u32, temp_offset: Option<f32>) -> (i16, i32) {
         let var1: i64 = (temp_adc as (i64) >> 3) - ((calib.par_t1 as (i64)) << 1);
         let var2: i64 = (var1 * (calib.par_t2 as i64)) >> 11;
         let var3: i64 = ((var1 >> 1) * (var1 >> 1)) >> 12;
         let var3: i64 = (var3 * ((calib.par_t3 as i64) << 4)) >> 14;
-        // TODO really assign here ?
-        let mut temp_offset = temp_offset.unwrap_or(0);
-        if temp_offset < 0 {
-            temp_offset = -1 * ((((temp_offset.abs() * 100) << 8) - 128) / 5);
-        }
+
+        let temp_offset =  match temp_offset {
+            None => 0i32,
+            Some(offset) if offset == 0.0 => 0i32,
+            Some(offset) => offset.signum() as i32 * (((((offset.abs() * 100.0) as i32) << 8) - 128) / 5),
+        };
 
         let t_fine: i32 = (var2 + var3) as i32  + temp_offset;
         let calc_temp: i16 = (((t_fine * 5) + 128) >> 8) as i16;

src/lib.rs

@@ -38,6 +38,8 @@
 //!     println!("Pressure {}hPa", data.pressure_hpa());
 //!     println!("Humidity {}%", data.humidity_percent());
 //!     println!("Gas Resistence {}Ω", data.gas_resistance_ohm());
+//!
+//!     Ok(())
 //! }
 //! ```
 

src/settings.rs

@@ -71,7 +71,7 @@ pub struct TphSett {
     /// Filter coefficient
     pub filter: Option<IIRFilterSize>,
     /// If set, the temperature t_fine will be increased by the given value in celsius.
-    pub temperature_offset: Option<i32>,
+    pub temperature_offset: Option<f32>,
 }
 
 impl Clone for TphSett {
@@ -148,12 +148,15 @@ bitflags! {
 ///
 /// # Example
 /// ```
+/// use bme680::{IIRFilterSize, OversamplingSetting, SettingsBuilder};
+/// use std::time::Duration;
 /// let settings = SettingsBuilder::new()
 ///     .with_humidity_oversampling(OversamplingSetting::OS2x)
 ///     .with_pressure_oversampling(OversamplingSetting::OS4x)
 ///     .with_temperature_oversampling(OversamplingSetting::OS8x)
 ///     .with_temperature_filter(IIRFilterSize::Size3)
 ///     .with_gas_measurement(Duration::from_millis(1500), 320, 25)
+///     .with_temperature_offset(-4.25)
 ///     .with_run_gas(true)
 ///     .build();
 /// ```
@@ -231,7 +234,7 @@ impl SettingsBuilder {
     }
 
     /// Temperature offset in Celsius, e.g. 4, -8, 1.25
-    pub fn with_temperature_offset(mut self, offset: i32) -> SettingsBuilder {
+    pub fn with_temperature_offset(mut self, offset: f32) -> SettingsBuilder {
         self.sensor_settings.tph_sett.temperature_offset = Some(offset);
         self
     }