altos: Try to get remote cmac time closer to reality

Record the time after the packet was sent, but before the return
packet arrives to try and more closely approximate the time the packet
arrived at the other end.

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

diff --git a/src/drivers/ao_lco_func.c b/src/drivers/ao_lco_func.c
index 152b5d1ba5b1d06e6c9b509a7b012597f88df036..99e58b76f872bc014e992ae622242cce1bc80701 100644 (file)
--- a/src/drivers/ao_lco_func.c
+++ b/src/drivers/ao_lco_func.c
@@ -28,18 +28,18 @@ ao_lco_query(uint16_t box, struct ao_pad_query *query, uint16_t *tick_offset)
 {
        uint8_t         i;
        int8_t          r;
-       uint16_t        time;
+       uint16_t        sent_time;
 
        ao_mutex_get(&ao_lco_mutex);
-       time = ao_time();
-       command.tick = time;
+       command.tick = ao_time() - *tick_offset;
        command.box = box;
        command.cmd = AO_LAUNCH_QUERY;
        command.channels = 0;
        ao_radio_cmac_send(&command, sizeof (command));
-       r = ao_radio_cmac_recv(query, sizeof (*query), AO_MS_TO_TICKS(500));
+       sent_time = ao_time();
+       r = ao_radio_cmac_recv(query, sizeof (*query), AO_MS_TO_TICKS(20));
        if (r == AO_RADIO_CMAC_OK)
-               *tick_offset = time - query->tick;
+               *tick_offset = sent_time - query->tick;
        ao_mutex_put(&ao_lco_mutex);
        return r;
 }