RX frames have two timestamps: monotonic - for protocol timings management; utc - for application-level timestamping

libuavcan/include/uavcan/can_driver.hpp

@@ -93,10 +93,17 @@ public:
 
     /**
      * Non-blocking reception.
-     * out_utc_timestamp_usec must be provided by the driver, ideally by the hardware CAN controller; 0 if unknown.
+     * Timestamps should be provided by the CAN driver, ideally by the hardware CAN controller.
+     * Monotonic timestamp is required and can be not precise since it is needed only for
+     * protocol timing validation (transfer timeouts and inter-transfer intervals).
+     * UTC timestamp is optional, if available it will be used for precise time synchronization;
+     * must be set to zero if not available.
+     * Refer to @ref ISystemClock to learn more about timestamps.
+     * @param [out] out_ts_monotonic_usec Monotonic timestamp, usec, mandatory.
+     * @param [out] out_ts_utc_usec       UTC timestamp, usec, optional, zero if unknown.
      * @return 1 = one frame received, 0 = RX buffer empty, negative for error.
      */
-    virtual int receive(CanFrame& out_frame, uint64_t& out_utc_timestamp_usec) = 0;
+    virtual int receive(CanFrame& out_frame, uint64_t& out_ts_monotonic_usec, uint64_t& out_ts_utc_usec) = 0;
 
     /**
      * Configure the hardware CAN filters. @ref CanFilterConfig.

libuavcan/include/uavcan/internal/transport/can_io.hpp

@@ -19,11 +19,13 @@ namespace uavcan
 
 struct CanRxFrame : public CanFrame
 {
-    uint64_t timestamp;
+    uint64_t ts_monotonic;
+    uint64_t ts_utc;
     uint8_t iface_index;
 
     CanRxFrame()
-    : timestamp(0)
+    : ts_monotonic(0)
+    , ts_utc(0)
     , iface_index(0)
     { }
 };

libuavcan/include/uavcan/internal/transport/transfer.hpp

@@ -137,11 +137,13 @@ struct Frame
 
 struct RxFrame : public Frame
 {
-    uint_fast64_t timestamp;
+    uint_fast64_t ts_monotonic;
+    uint_fast64_t ts_utc;
     uint_fast8_t iface_index;
 
     RxFrame()
-    : timestamp(0)
+    : ts_monotonic(0)
+    , ts_utc(0)
     , iface_index(0)
     { }
 
@@ -149,7 +151,8 @@ struct RxFrame : public Frame
     {
         if (!Frame::parse(can_frame))
             return false;
-        timestamp = can_frame.timestamp;
+        ts_monotonic = can_frame.ts_monotonic;
+        ts_utc = can_frame.ts_utc;
         iface_index = can_frame.iface_index;
         return true;
     }

libuavcan/include/uavcan/internal/transport/transfer_receiver.hpp

@@ -23,9 +23,10 @@ private:
     enum TidRelation { TID_SAME, TID_REPEAT, TID_FUTURE };
     enum { IFACE_INDEX_NOTSET = 0xFF };
 
-    uint64_t prev_transfer_timestamp_;
-    uint64_t this_transfer_timestamp_;
-    uint64_t transfer_interval_;
+    uint64_t prev_transfer_ts_monotonic_;
+    uint64_t this_transfer_ts_monotonic_;
+    uint64_t first_frame_ts_utc_;
+    uint64_t transfer_interval_;            // TODO: make 32 bit
     ITransferBufferManager* bufmgr_;
     TransferBufferManagerKey bufmgr_key_;
     TransferID tid_;
@@ -48,8 +49,9 @@ private:
 
 public:
     TransferReceiver()
-    : prev_transfer_timestamp_(0)
-    , this_transfer_timestamp_(0)
+    : prev_transfer_ts_monotonic_(0)
+    , this_transfer_ts_monotonic_(0)
+    , first_frame_ts_utc_(0)
     , transfer_interval_(DEFAULT_TRANSFER_INTERVAL)
     , bufmgr_(NULL)
     , iface_index_(IFACE_INDEX_NOTSET)
@@ -57,8 +59,9 @@ public:
     { }
 
     TransferReceiver(ITransferBufferManager* bufmgr, const TransferBufferManagerKey& bufmgr_key)
-    : prev_transfer_timestamp_(0)
-    , this_transfer_timestamp_(0)
+    : prev_transfer_ts_monotonic_(0)
+    , this_transfer_ts_monotonic_(0)
+    , first_frame_ts_utc_(0)
     , transfer_interval_(DEFAULT_TRANSFER_INTERVAL)
     , bufmgr_(bufmgr)
     , bufmgr_key_(bufmgr_key)
@@ -74,8 +77,9 @@ public:
     TransferReceiver& operator=(const TransferReceiver& rhs)
     {
         cleanup();
-        prev_transfer_timestamp_ = rhs.prev_transfer_timestamp_;
-        this_transfer_timestamp_ = rhs.this_transfer_timestamp_;
+        prev_transfer_ts_monotonic_ = rhs.prev_transfer_ts_monotonic_;
+        this_transfer_ts_monotonic_ = rhs.this_transfer_ts_monotonic_;
+        first_frame_ts_utc_ = rhs.first_frame_ts_utc_;
         transfer_interval_ = rhs.transfer_interval_;
         bufmgr_ = rhs.bufmgr_;
         tid_ = rhs.tid_;
@@ -89,7 +93,8 @@ public:
 
     ResultCode addFrame(const RxFrame& frame);
 
-    uint64_t getLastTransferTimestamp() const { return prev_transfer_timestamp_; }
+    uint64_t getLastTransferTimestampMonotonic() const { return prev_transfer_ts_monotonic_; }
+    uint64_t getLastTransferTimestampUtc() const { return first_frame_ts_utc_; }
 
     uint64_t getInterval() const { return transfer_interval_; }
 };