VCI - Virtual CAN Interface - Ixxat

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Accessing the busAfter a message channel has been opened, it must first be initialized. This is donewith the function canChannelInitialize. The function expects as input parametersthe size of the receive and transmit buffers in number of CAN messages and thethreshold values for the receive or transmit event.The memory reserved for the receive and transmit buffers comes from a limitedsystem memory pool. The individual buffers of a message channel should thereforenot contain more than approx. 2000 messages.The receive event of a channel is triggered when the receive buffer contains atleast the number of messages specified in wRxThreshold. The transmit event istriggered when the transmit buffer has at least sufficient space for the number ofmessages specified in wTxThreshold.If the channel has been created, it can be enabled or disabled with the functioncanChannelActivate. The channel is enabled when the function is called with thevalue TRUE in the parameter fEnable. The channel is disabled by calling the functionwith the value FALSE in the parameter fEnable. A channel is disabled afteropening as the default setting.Messages are only received by the CAN controller or sent to it if the channel isactive. In addition, the CAN controller must be started, otherwise no messagetransfer takes place between the CAN bus and the channel. The message filter ofthe CAN controller also has an influence on the received messages. More informationon this is given in section 3.1.2.A message channel is closed with the function canChannelClose. The functionshould always be called when a channel is no longer needed.3.1.3.1 Reception of CAN messagesThe simplest way of reading received messages from the receive buffer is to callthe function canChannelReadMessage. If there are no messages available in thereceive buffer, the function waits until either a new message is received or thewaiting time specified in the parameter dwMsTimeout has expired. Every messagehas a associated message type (data, info, error, status, timer-overrun). (see§5.2.5 CANMSGINFO)The function canChannelPeekMessage also reads the next message from the receivebuffer. In contrast to canChannelReadMessage, however, the function doesnot wait for a new message but returns immediately to the calling program witha corresponding error code if no message is available in the receive buffer.It is possible to wait for a new receive message or the occurrence of the receiveevent with the function canChannelWaitRxEvent. The receive event is triggeredwhen the receive buffer contains at least the number of messages specified inwRxThreshold when canChannelInitialize is called.The following code fragment shows a possible use of the functions canChannel-WaitRxEvent and canChannelPeekMessage.22Copyright IXXAT Automation GmbH C-API Programming Manual, Version 1.5
Accessing the busDWORD WINAPI ReceiveThreadProc( LPVOID lpParameter ){HANDLE hChannel = (HANDLE) lpParameter;CANMSG sCanMsg;while (canChannelWaitRxEvent(hChannel, INFINITE) == VCI_OK){while (canChannelPeekMessage(hChannel, &sCanMsg) == VCI_OK)}{}// processing of the message}return 0;Note that the thread procedure only ends when the function canChannelWaitRxEventreturns an error code not equal to VCI_OK. However, when correctlycalled, all message channel-specific functions only return an error code not equalto VCI_OK when a serious problem has occurred.A program-controlled “normal” abort of the thread procedure from the previousexample does not therefore appear to be possible. However, it is possible to closethe handle of the message channel from another thread, where all currently outstandingfunction calls or all new calls end with an error code not equal toVCI_OK. However, the disadvantage of this is that any transmit threads runningsimultaneously are also affected.3.1.3.2 Transmission of CAN messagesThe easiest way of transmitting CAN messages to the bus is to call the functioncanChannelSendMessage. The function waits until sufficient space is available inthe message channel and then writes the message in a free entry in the transmitbuffer. If it was possible to enter the message in the transmit buffer in the timespecified in dwMsTimeout, the function returns the value VCI_OK. If the specifiedtime has elapsed without the message being written in the transmit buffer, thefunction returns the value VCI_E_TIMEOUT.The function canChannelPostMessage also writes a CAN message in the transmitbuffer. Unlike canChannelSendMessage, however, the function does not wait untilsufficient space is available in the transmit buffer but returns to the callingprogram with an error code if no free entry is available.It is possible to wait for the occurrence of transmit events with the function can-ChannelWaitTxEvent. The transmit event is triggered when the transmit bufferhas at least enough space for the number of messages specified in wTxThresholdwhen canChannelInitialize is called.The following code fragment shows a possible use of the functions canChannel-WaitTxEvent and canChannelPostMessage.23Copyright IXXAT Automation GmbH C-API Programming Manual, Version 1.5
Page 8 and 9: System overviewThe VCI server runni
Page 10 and 11: Device management and device access
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Page 24 and 25: Accessing the busHRESULT hResult;HA
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Page 36 and 37: Interface description4 Interface de
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Interface description4.3.3.4 canSch
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Interface description4.3.3.7 canSch
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Interface description4.3.3.10 canSc
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Interface description4.4.1.3 linCon
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Interface description4.4.1.6 linCon
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Interface description4.4.2.1 linMon
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Interface descriptionReturn value:I
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Types and structures• VciObjectId
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Types and structures• wBusCouplin
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Types and structures• dwStatus:[o
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Types and structures5.2.5 CANMSGINF
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Types and structuresCAN_MSGTYPE_STA
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Types and structures5.2.7 CANCYCLIC
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Types and structures• dwClockFreq
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Types and structuresThe information
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Types and structures• Bits.ovr:[o
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VCI - Virtual CAN Interface - Ixxat

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