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icE1usb fw/gpsdo: If no PPS present for >= 3s, go to hold over mode

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Change-Id: Ia85a8bb0e146cb117ea6e2704c6a4dedf215c75a
---
M firmware/ice40-riscv/icE1usb/gpsdo.c
1 file changed, 11 insertions(+), 0 deletions(-)

diff --git a/firmware/ice40-riscv/icE1usb/gpsdo.c b/firmware/ice40-riscv/icE1usb/gpsdo.c
index 573c0bb..2481c2e 100644
--- a/firmware/ice40-riscv/icE1usb/gpsdo.c
+++ b/firmware/ice40-riscv/icE1usb/gpsdo.c
@@ -15,6 +15,8 @@
 
 #include "ice1usb_proto.h"
 
+#include "config.h"
+
 
 struct {
 	/* Configuration */
@@ -275,6 +277,14 @@
 	uint32_t tick_now, tick_diff;
 	bool valid;
 
+	/* If more than 3 sec elapsed since last PPS, go to hold-over */
+	if (time_elapsed(g_gpsdo.meas.tick_prev, 3 * SYS_CLK_FREQ)) {
+		g_gpsdo.state = STATE_HOLD_OVER;
+		g_gpsdo.meas.invalid = 0;
+		g_gpsdo.meas.skip = 0;
+		return;
+	}
+
 	/* Get current tick and check if there was a PPS and estimate frequency */
 	tick_now = time_pps_read();
 
@@ -299,6 +309,7 @@
 		/* No GPS fix, go to hold-over */
 		g_gpsdo.state = STATE_HOLD_OVER;
 		g_gpsdo.meas.invalid = 0;
+		g_gpsdo.meas.skip = 0;
 		return;
 	}
 

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