altos: MS5607 pressure computation for low temperatures was wrong

[fw/altos] / src / drivers / ao_ms5607_convert.c

diff --git a/src/drivers/ao_ms5607_convert.c b/src/drivers/ao_ms5607_convert.c
index e61d19ed61d637eee6fff3e48982cdc82856062b..bfb952a47e7b2c8a1da54701a34765d6cd7e38f3 100644 (file)
--- a/src/drivers/ao_ms5607_convert.c
+++ b/src/drivers/ao_ms5607_convert.c
@@ -42,11 +42,14 @@ ao_ms5607_convert(struct ao_ms5607_sample *sample, struct ao_ms5607_value *value
                int32_t TEMPM = TEMP - 2000;
                int64_t OFF2 = (61 * (int64_t) TEMPM * (int64_t) TEMPM) >> 4;
                int64_t SENS2 = 2 * (int64_t) TEMPM * (int64_t) TEMPM;
-               if (TEMP < 1500) {
+               if (TEMP < -1500) {
                        int32_t TEMPP = TEMP + 1500;
-                       int64_t TEMPP2 = TEMPP * TEMPP;
-                       OFF2 = OFF2 + 15 * TEMPP2;
-                       SENS2 = SENS2 + 8 * TEMPP2;
+                       /* You'd think this would need a 64-bit int, but
+                        * that would imply a temperature below -327.67°C...
+                        */
+                       int32_t TEMPP2 = TEMPP * TEMPP;
+                       OFF2 = OFF2 + (int64_t) 15 * TEMPP2;
+                       SENS2 = SENS2 + (int64_t) 8 * TEMPP2;
                }
                TEMP -= T2;
                OFF -= OFF2;