canalystii: Fix transmitting onto a busy bus (hardbyte#1114)

* canalystii: Add a note about the library

* canalystii: Retry if sending fails the first time

Author: projectgus

can/interfaces/canalystii.py

@@ -32,6 +32,9 @@ class VCI_CAN_OBJ(Structure):
     ]
 
 
+SENDTYPE_ALLOW_RETRY = 0  # Retry send if there is bus contention
+SENDTYPE_ONE_SHOT = 1  # Drop the message if transmission fails first time
+
 VCI_USBCAN2 = 4
 
 STATUS_OK = 0x01
@@ -145,7 +148,7 @@ def send(self, msg, timeout=None):
             msg.arbitration_id,
             0,
             0,
-            1,
+            SENDTYPE_ALLOW_RETRY,
             msg.is_remote_frame,
             extern_flag,
             msg.dlc,

doc/interfaces/canalystii.rst

@@ -4,6 +4,9 @@ CANalyst-II
 CANalyst-II(+) is a USB to CAN Analyzer. The controlcan library is originally developed by
 `ZLG ZHIYUAN Electronics`_.
 
+.. note::
+
+   Use of this interface requires the ``ControlCAN.dll`` (Windows) or ``libcontrolcan.so`` vendor library to be placed in the Python working directory.
 
 Bus
 ---