From: Keith Packard <keithp@keithp.com>
Date: Mon, 10 Dec 2012 02:27:49 +0000 (-0800)
Subject: altos: Make sure pa to altitude conversion is done with 32 bits
X-Git-Tag: micropeak-build-2012-12-09~1
X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=defd5d0784a754be30e3295067fbc85a108ad172

altos: Make sure pa to altitude conversion is done with 32 bits

We need 32 bits to hold intermediate values, even if the final
altitude is reported in only 16 bits.

Signed-off-by: Keith Packard <keithp@keithp.com>
---

diff --git a/src/core/ao_convert_pa.c b/src/core/ao_convert_pa.c
index 55fe6e7d..fe6e0ef6 100644
--- a/src/core/ao_convert_pa.c
+++ b/src/core/ao_convert_pa.c
@@ -43,13 +43,13 @@ ao_pa_to_altitude(int32_t pa)
 
 	if (pa < 0)
 		pa = 0;
-	if (pa > 120000)
-		pa = 120000;
+	if (pa > 120000L)
+		pa = 120000L;
 	o = pa >> ALT_SHIFT;
 	part = pa & ALT_MASK;
 
-	low = (alt_t) FETCH_ALT(o) * (ALT_SCALE - part);
-	high = (alt_t) FETCH_ALT(o+1) * part + (ALT_SCALE >> 1);
+	low = (int32_t) FETCH_ALT(o) * (ALT_SCALE - part);
+	high = (int32_t) FETCH_ALT(o+1) * part + (ALT_SCALE >> 1);
 	return (low + high) >> ALT_SHIFT;
 }
 
diff --git a/src/micropeak/ao_pins.h b/src/micropeak/ao_pins.h
index 187b2544..63e9cb1b 100644
--- a/src/micropeak/ao_pins.h
+++ b/src/micropeak/ao_pins.h
@@ -60,6 +60,6 @@
 typedef int32_t alt_t;
 #define FETCH_ALT(o)		((alt_t) pgm_read_dword(&altitude_table[o]))
 
-#define AO_ALT_VALUE(x)		((x) * 10)
+#define AO_ALT_VALUE(x)		((x) * (alt_t) 10)
 
 #endif /* _AO_PINS_H_ */