Switch to using internal cc1111 temperature sensor

[fw/altos] / ao-tools / lib / cc-convert.c

diff --git a/ao-tools/lib/cc-convert.c b/ao-tools/lib/cc-convert.c
index ac6962ba254e6a82ef000f62631e2dafd172718e..8d6876a064422a202fd7d3de99ea6ecd3cc4174e 100644 (file)
--- a/ao-tools/lib/cc-convert.c
+++ b/ao-tools/lib/cc-convert.c
@@ -213,10 +213,19 @@ cc_accelerometer_to_acceleration(double accel, double ground_accel)
        return (ground_accel - accel) / count_per_mss;
 }
 
+/* Value for the CC1111 built-in temperature sensor
+ * Output voltage at 0°C = 0.755V
+ * Coefficient = 0.00247V/°C
+ * Reference voltage = 1.25V
+ *
+ * temp = ((value / 32767) * 1.25 - 0.755) / 0.00247
+ *      = (value - 19791.268) / 32768 * 1.25 / 0.00247
+ */
+
 double
 cc_thermometer_to_temperature(double thermo)
 {
-       return ((thermo / 32767 * 3.3) - 0.5) / 0.01;
+       return (thermo - 19791.268) / 32728.0 * 1.25 / 0.00247;
 }
 
 double