Perform no-delay time synchronization

[~andy/csm213a-hw] / hw2 / main.cpp

diff --git a/hw2/main.cpp b/hw2/main.cpp
index d32dd0c78cd68cd3baded568d12bbbdd8ace9dad..3e82918134cc36d645b4ab454a9d9e56ae9b6e14 100644 (file)
--- a/hw2/main.cpp
+++ b/hw2/main.cpp
@@ -220,18 +220,12 @@ typedef struct {
 
 static uint32_t serial_device_id   = 0;
 
-const  uint64_t serial_sync_delay  = NSEC_PER_SEC / 100; // 1hz
+const  uint64_t serial_sync_delay  = NSEC_PER_SEC / 100;
 static uint64_t serial_sync_due    = 0;
 
 static tdma_t  *serial_tdma_rcv    = NULL;
 static tdma_t  *serial_tdma_xmt    = NULL;
 
-static uint64_t serial_prev_local  = 0;
-static uint64_t serial_prev_seq    = 0;
-
-static uint64_t serial_xmt_local   = 0;
-static uint64_t serial_xmt_seq     = 0;
-
 /**
  * Convert world to local time
  */
@@ -249,6 +243,20 @@ ntime_t serial_write_time(uint64_t time)
        return buf;
 }
 
+int serial_time_stamp(tdma_t *port, uint64_t *local, uint64_t *world,
+               const char *msg)
+{
+       int valid = tdma_stamp(port, local);
+       *world = time_to_world(*local);
+
+       if (!valid)
+               sirq_printf("%s -- missing\r\n", msg);
+       //else
+       //      time_printf(msg, current);
+
+       return valid;
+}
+
 /**
  * Output initialization message init message
  */
@@ -264,45 +272,41 @@ void serial_send_sync(sirq_t *port, uint64_t now)
        if (serial_sync_due == 0 || now < serial_sync_due)
                return; // not ready
 
-       //sirq_printf("sending sync\r\n");
-
-       // Calculate world time
-       uint64_t local = 0;
-       uint64_t world = time_to_world(serial_xmt_local);
-
        // Message data
        header_t   head;
        sync_msg_t body;
 
-       // Transmit sync message
+       // Write header
        head.header = MSG_HEADER;
        head.msgid  = MSG_ID_SYNC;
        head.length = sizeof(body);
        head.cksum  = 0; // todo
 
-       body.seq          = serial_xmt_seq;
-       body.time.seconds = world / NSEC_PER_SEC;
-       body.time.nanosec = world % NSEC_PER_SEC;
-
-       tdma_stop(serial_tdma_rcv);
-
+       tdma_stop(serial_tdma_rcv, 0);
        tdma_start(serial_tdma_xmt);
-       sirq_write(port, &head, sizeof(head));
-       sirq_write(port, &body, sizeof(body));
-       tdma_stop(serial_tdma_xmt);
 
-       // save transmit time
-       int valid = tdma_stamp(serial_tdma_xmt, &local);
-       if (!valid)
-               sirq_printf("sync transmit time -- missed\r\n");
-       else
-               //time_printf("sync transmit time ", local);
+       sirq_write(port, &head, sizeof(head));
 
+       tdma_stop(serial_tdma_xmt, 100);
        tdma_start(serial_tdma_rcv);
 
-       serial_xmt_seq  += 1;
+       // Save transmit time
+       uint64_t local = 0, world = 0;
+       serial_time_stamp(serial_tdma_xmt, &local, &world,
+                       "sync time transmit");
+
+       // Debug output
+       //sirq_printf("sync time transmit\r\n");
+       //time_printf("  local", local);
+       //time_printf("  world", world);
+
+       // Write body with updated time and send
+       body.time = serial_write_time(world);
+
+       sirq_write(port, &body, sizeof(body));
+
+       // Queue next transmit time
        serial_sync_due  = 0;
-       serial_xmt_local = local;
 }
 
 /**
@@ -380,31 +384,26 @@ void serial_handle_init(init_msg_t *msg)
  */
 void serial_handle_sync(sync_msg_t *msg)
 {
-       // Read receive timestamp for next time sync message
-       uint64_t current = 0;
-       int valid = tdma_stamp(serial_tdma_rcv, &current);
-       if (!valid)
-               sirq_printf("sync receive time  -- missing\r\n");
-       //else
-       //      time_printf("sync receive time ", current);
-       tdma_stop(serial_tdma_rcv);
+       // Read receive timestamp
+       uint64_t local = 0, world = 0;
+       serial_time_stamp(serial_tdma_rcv, &local, &world,
+                       "sync time receive ");
+       tdma_stop(serial_tdma_rcv, 0);
 
-       // Lookup times
-       uint64_t world = ((uint64_t)msg->time.seconds) * NSEC_PER_SEC
-                      + ((uint64_t)msg->time.nanosec);
+       // Lookup reference time from message
+       uint64_t reference = serial_read_time(msg->time);
 
-       // Valid times timestamp
-       if (serial_prev_seq == (msg->seq-1)) {
-               uint64_t local = serial_prev_local;
-               time_ext_sync(local, world);
-       }
+       // Debug output
+       //sirq_printf("sync time receive\r\n");
+       //time_printf("  local", local);
+       //time_printf("  world", world);
+       //time_printf("  ref  ", reference);
+
+       // Synchronize the clocks
+       time_ext_sync(local, reference);
 
        // Queue transmit to other board
        serial_sync_due   = tdma_time() + serial_sync_delay;
-
-       // Update states
-       serial_prev_local = current;
-       serial_prev_seq   = msg->seq;
 }
 
 /**
@@ -541,7 +540,7 @@ void task_events(uint64_t local, uint64_t world)
 
        if (tdma_stamp(tdma_evt, &event))
                serial_send_event(sirq_bbb, 0, event);
-       tdma_stop(tdma_evt);
+       tdma_stop(tdma_evt, 0);
        tdma_start(tdma_evt);
 }