altos: Expose a signed version of the tick count

Useful when doing time comparisons.

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

diff --git a/src/stm/ao_arch.h b/src/stm/ao_arch.h
index d0dd3c7976d432a32557399c5fb6b36e4c38c6a2..87eda18b2a89878a2576d79f90bed05ab0e51a39 100644 (file)
--- a/src/stm/ao_arch.h
+++ b/src/stm/ao_arch.h
@@ -31,6 +31,7 @@
 
 #ifndef AO_TICK_TYPE
 #define AO_TICK_TYPE   uint16_t
+#define AO_TICK_SIGNED int16_t
 #endif
 
 /* Various definitions to make GCC look more like SDCC */