From 55524b7bd2e4dac25bd2b384ea8bde7fded40a05 Mon Sep 17 00:00:00 2001
From: zariiii9003 <52598363+zariiii9003@users.noreply.github.com>
Date: Mon, 21 Oct 2024 15:05:48 +0200
Subject: [PATCH 1/2] get timestamp offset after canBusOn

---
 can/interfaces/kvaser/canlib.py | 36 ++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/can/interfaces/kvaser/canlib.py b/can/interfaces/kvaser/canlib.py
index 5501c311d..84b7f768b 100644
--- a/can/interfaces/kvaser/canlib.py
+++ b/can/interfaces/kvaser/canlib.py
@@ -573,6 +573,23 @@ def __init__(
         )
         canSetBusOutputControl(self._write_handle, can_driver_mode)
 
+        self._is_filtered = False
+        super().__init__(
+            channel=channel,
+            can_filters=can_filters,
+            **kwargs,
+        )
+
+        # activate channel after CAN filters were applied
+        log.debug("Go on bus")
+        if not self.single_handle:
+            canBusOn(self._read_handle)
+        canBusOn(self._write_handle)
+
+        # timestamp must be set after bus is online
+        self._timestamp_offset = self._update_timestamp_offset()
+
+    def _update_timestamp_offset(self) -> float:
         timer = ctypes.c_uint(0)
         try:
             if time.get_clock_info("time").resolution > 1e-5:
@@ -580,28 +597,15 @@ def __init__(
                 kvReadTimer(self._read_handle, ctypes.byref(timer))
                 current_perfcounter = time.perf_counter()
                 now = ts + (current_perfcounter - perfcounter)
-                self._timestamp_offset = now - (timer.value * TIMESTAMP_FACTOR)
+                return now - (timer.value * TIMESTAMP_FACTOR)
             else:
                 kvReadTimer(self._read_handle, ctypes.byref(timer))
-                self._timestamp_offset = time.time() - (timer.value * TIMESTAMP_FACTOR)
+                return time.time() - (timer.value * TIMESTAMP_FACTOR)
 
         except Exception as exc:
             # timer is usually close to 0
             log.info(str(exc))
-            self._timestamp_offset = time.time() - (timer.value * TIMESTAMP_FACTOR)
-
-        self._is_filtered = False
-        super().__init__(
-            channel=channel,
-            can_filters=can_filters,
-            **kwargs,
-        )
-
-        # activate channel after CAN filters were applied
-        log.debug("Go on bus")
-        if not self.single_handle:
-            canBusOn(self._read_handle)
-        canBusOn(self._write_handle)
+            return time.time() - (timer.value * TIMESTAMP_FACTOR)
 
     def _apply_filters(self, filters):
         if filters and len(filters) == 1:

From fbb725e8997581aa3066fde18c4d3f65f674a86c Mon Sep 17 00:00:00 2001
From: zariiii9003 <52598363+zariiii9003@users.noreply.github.com>
Date: Fri, 25 Oct 2024 16:22:01 +0200
Subject: [PATCH 2/2] update comment

---
 can/interfaces/kvaser/canlib.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/can/interfaces/kvaser/canlib.py b/can/interfaces/kvaser/canlib.py
index 84b7f768b..51a77a567 100644
--- a/can/interfaces/kvaser/canlib.py
+++ b/can/interfaces/kvaser/canlib.py
@@ -586,7 +586,7 @@ def __init__(
             canBusOn(self._read_handle)
         canBusOn(self._write_handle)
 
-        # timestamp must be set after bus is online
+        # timestamp must be set after bus is online, otherwise kvReadTimer may return erroneous values
         self._timestamp_offset = self._update_timestamp_offset()
 
     def _update_timestamp_offset(self) -> float: