I am looking to test a scenario, how my software will respond to disconnection of a particular CAN message coming from an external device. This external device will send many CAN messages in the bus, so I cannot control it to stop just a particular message.
Therefore, I am looking for a way in CANoe just to stop one particular CAN message coming into the bus.
Please need your suggestions here.
I tried to provide as much information here, if more is require kindly put in the comment. Thanks.
You would have to split the bus into two and configure CANoe to act as a gateway:
You need a network interface with two CAN channels.
You connect your DUT to one channel (say CAN2) and the remaining bus to the other channel (CAN1).
You then configure both busses in CANoe and add a node to both busses in the simulation setup.
This node should listen to all messages received on CAN1 and output them to CAN2 and vice versa.
If you want certain messages not to reach CAN2, you have to adapt the logic of this node.
Refer to this article in the Vector knowlegde base on how to setup a gateway between two CAN busses and how to control the message flow between those busses.
Related
I am new to CAN communication and one of my tasks is to use a CANalyzer to learn what message IDs are being used for a product and what data is being sent/received.
The product has multiple nodes that can send/receive CAN messages. I know CAN messages are broadcasted to all the nodes, but the part I'm having a hard time determining is which node transmitted the message and which nodes received it.
So, for example, if I have 3 CAN nodes, is there a way I can determine that Node 1 sent the message and Node 2/3 are receiving the message?
Thank you in advance.
Generally, you can't know this by listening to the CAN bus alone. The same old story whenever someone asks about data on "CAN bus" is: what application layer protocol is it using? "CAN bus" doesn't tell you jack, it's just the specification physical and data link layers. The concept of identifying individual nodes does not exist on the data link layer, only on the application layer.
There's two possible ways for you to tell:
If you know the application layer used on top of the physical CAN bus and know that it uses node id, then you can tell which node that is sending what data by decoding the application-layer protocol.
On each node, you can sniff the Tx signal between the MCU and CAN transceiver with an oscilloscope. That one only goes active when a node is sending or ACK:ing. Most modern scopes has a CAN frame decoder feature, saving you the head ache of decoding the frames manually.
Hey Stackoverflow community :)
Im looking into making a camera stream video from a an RC device into a computer using wifi.
After considering all of the options I had Im left with two:
use UDP to transfer video in packets
use packet injection and packet sniffing on the receiving device.
I was wondering what are the pros and cons of each method (for that specific purpose of video transmission)?
after looking around I found many implementations for both ways but nowhere have they specified why one is better than the other.
few things that I have not mentioned:
I know UDP does not have error correction which can make the video weird- I dont care about the quality of the video as long as it will be recognizeable.
I dont want to use connection based protocol (TPC, etc)- I dont want to wait for handshake when I get disconnected.
thanks :)
I'm trying to do a similar thing. My take on this is basically when you use the wifi cards in monitor mode (i.e. using packet sniffing/injection) you don't actually need to be connected to that network. Typically, you still need to be connected to an Access point as a client then you can communicate using UDP through that connection. But, in this case, the UDP messages are routed to the Wifi cards and the packets are injected out without being associated with any client. Then, any 'client' just has to sniff or listen on that same channel to get the transmission. So the benefit is not only does UDP not check for lost frames/etc, but also in this case you don't need to be connected to the network to get the packets.
In my case, this is preferable, since basically you will need to connect to the AP in the former case and that would require more capable hardware on the receiver side typically (more range is needed for the association part since you need to send messages back over TCP essentially to get it connected).
FYI here are the links/repos I am using and it also is a reference to what I am talking about
https://docs.px4.io/master/en/tutorials/video_streaming_wifi_broadcast.html
https://github.com/svpcom/wifibroadcast
I am using an off the shelf 'solution' in the short term, the Accsoon Cineye Air, which basically transmits HDMI 300ft line of sight over WiFi. You need an android phone to receive it, and basically I'm using the Vysor application (paid version is $40) to mirror the screen to my desktop. It works, but the latency is still more than I want : 60ms at least from the cineeye, so you can drive it around but its not as quick as DJI which is around 30-40ms ), which is my goal.
How does the sender on the CAN bus know that a node has not properly received the data?
I am currently learning the functioning of the CAN bus. Based on what I have seen so far a receiver drives the bus to a dominant state when it successfully obtains a packet and one receiving node is enough to accomplish this. However, in the event where the intended receiver does not successfully obtain the packet while others do, how is the sender made aware of the situation so that it can retransmit the packet?
Any help in providing some clarity on this topic is much appreciated. Thank you.
The sender can't know this unless you implement a higher layer protocol. The ACK slot in raw CAN frame allows sender to detect if it (not the receiver) has a bus problem. If the sender doesn't sample an ACK, it can conclude that "No one is hearing me in the bus. Maybe I'm physically disconnected or something is completely wrong."
For example in CANopen, it's generally receivers job to complain if an expected PDO packet doesn't arrive on time. Although it's not correct to talk about masters and slaves in CAN bus, a device you assign a master role can be programmed to expect periodic PDO report packets from its slaves, and can rise an error flag if they don't arrive in expected time window.
I have a virtual socketCAN network. How do I block a particular ID from being sent on the network?
If a node is connected to a CAN bus, at the lowest level it cannot be prevented from sending any message externally.
However, there are 3 things that can be done:
Add a gateway - a device that separates the bus into multiple small buses and passes messages from each sub-buses to the others, it does not prevent any node from sending a message, but it will not pass it to the others. This solution have a few clear drawbacks - it requires a separate device with multiple CAN interfaces (up to the number of nodes on the bus), it adds a delay for each message, and it renders the ACK bit unusable.
Apply filters for the received messages in each node. Again, this will not prevent sending the message, but will drop the load on the nodes. Most CAN controllers have hardware support for filtering by ID or a bit mask of ID.
There are some CAN controllers that can block the sending of messages, again, this will require adding such controller and setting it up for each node in the CAN bus.
I want to implement a demo application to listen data via TCP/IP.
Data Transmitter will transmit a series or ASCII char or a series of string all the time. It feeds data into TCP/IP address (eg. 127.0.0.1:22) This could be a GPS transmitter.
I want to implement a demo application for receiving data by clicking the start button and listening to the data via TCP/IP and display it accordingly.
Correct me if I am wrong, I don't think I can use Server/Client server for this purpose. I tried to create a client application with TIdTcpClient, it receives only one time data. I don't think Indy has a TCP listening component.
Thanks in advance.
If you wanna monitor network comunications between some device and some other program on your computer using of TIdTCPServer won't work. Why? Once Indy will read network data it will mark it as processed and delete it from network buffer. So that data probably won't even reach to the other program on your computer. Workaround for this is that you design your application to actually work similar as network bridge. Your application listens to the data on one port and then forwards that data on another port on which the other program is listening. But the main problem is that you have to make this to work both ways.
What you need is somekind of a component which is able to peek at the network data but don't interact with it. This is usually done on driver level.
Now if it is not abolutely necessary to have such functionality in your own software but you are only interested in getting the data I recomend you try Wireshark (http://www.wireshark.org/). Wireshark is a verry powerfull freware software which alows you to monitor all netwrok traffic on basically all protocols without causing any interuptions. In order for this software to work it instals special driver which serves for intercepting the network data.
Maybe you would want to use same driver in your application if this functionality needs to be in your application.
Based on your diagram I think that your implementation could also be based on a message-oriented middleware, using a message broker which receives the GPS transmitter or other data.
The message broker would then store the data internally and forward it to all interested clients which are connected. A typical messaging pattern in this case is a "Topic", which broadcasts the messages similar to a radio station.
So the middleware will ensure that the information will be collected (optionally also persisted to disk) and then guarantees the delivery to the receivers. This can be done even in a way where receivers which have been off-line for a while still receive the GPS messages created while they where not listening ('retroactive consumers').
There are many popular free open source message brokers, and most of them also can be used with Delphi.