From cd920a0e5321166ef8b1d6afc3d63fc5de998a93 Mon Sep 17 00:00:00 2001 From: Keith Packard Date: Mon, 25 Feb 2019 16:42:25 -0700 Subject: altos: add ao_time_ns API This provides nano-second resolution times by reading the systick value (which runs at 250ns ticks on stm). Signed-off-by: Keith Packard --- src/lpc/ao_timer_lpc.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'src/lpc') diff --git a/src/lpc/ao_timer_lpc.c b/src/lpc/ao_timer_lpc.c index 50313333..62b16318 100644 --- a/src/lpc/ao_timer_lpc.c +++ b/src/lpc/ao_timer_lpc.c @@ -18,6 +18,8 @@ #include +#define AO_SYSTICK (AO_LPC_SYSCLK / 2) + volatile AO_TICK_TYPE ao_tick_count; AO_TICK_TYPE @@ -26,6 +28,22 @@ ao_time(void) return ao_tick_count; } +uint64_t +ao_time_ns(void) +{ + AO_TICK_TYPE before, after; + uint32_t cvr; + + do { + before = ao_tick_count; + cvr = lpc_systick.cvr; + after = ao_tick_count; + } while (before != after); + + return (uint64_t) after * (1000000000ULL / AO_HERTZ) + + (uint64_t) cvr * (1000000000ULL / AO_SYSTICK); +} + #if AO_DATA_ALL volatile uint8_t ao_data_interval = 1; volatile uint8_t ao_data_count; -- cgit v1.2.3