CAN interview questions

[sivamit]

Hi,
anyone has CAN interview question related docs or website..?
Please post it..
Next week I have 2-3 interviews related to automotive..help

 

[vijay s]

hai you got any CAN interview questions in this long period... please share if u got some

 

[vijay s]

in one interview i faced a question.. what is Mask Filter


oops.. No reply... No body working with CAN

 

[VirtualThread]

Some CAN controllers provide you a mechanism to filter out the reception of messages at hardware level. You set the mask filter and if the ID of an incoming message passes that filter only then it is received and the controller is interrupted.

In mask filter you can specify which bits of an incoming acceptable message must be DOMINANT, which must be RECESSIVE and which one are don't care.

 

[vijay s]

@virtual thread
can you share some more questions on CAN

 

[btbass]

CAN questions:

Describe the format of the following standard can frames:

Standard data frame
Extended data frame
Remote frame
Error frame
Overload frame
Interframe space.

Explain the following terms:

Tq
Propagation time segment = 8Tq
Phase buffer Segment 1 = 6Tq
Phase buffer Segment 2 = 5Tq
Synchronized jump width = 4Tq

What is bit stuffing?

How is message priority resolved when two frames collide?

If you can answer the above. Your hired!

 

[VirtualThread]

btbas has given you right hints. In general you should go through the protocol description to be ready to answer any questions. Let me give you a few examples to test your understanding after you have gone through the protocol specs.

What is the difference between a standard and an extended CAN frame. Can they coexist on a network?

If they can co-exist, which one will have priority; if not, what is the reason?

Describe some problems associated with multimaster protocols. How does CAN handle them?

Describe the process of bus arbitration in CAN?

What's the difference between CSMA/CR and CSMA/CD?

How can we identify a specific sensor in a CAN network?

Which of the RTR and Data frame has higher priority. Explain why?

What is bus termination resistor value for CAN? Do they vary if we put them in each node instead of bus ends?

etc. etc.

 

[svhb]

maybe also something about maximum cable lengths? Why? and how to calculate?

 

[vijay s]

Thank you guys for sharing....

@virtualThread
How can we identify a specific sensor in a CAN network?

can u please answer this....

What is the difference between CAN Bus and its higher layer protocols

 

[VirtualThread]

This question is more like the start of a discussion and will depend upon how you and the interviewer carry this.

One can say that at CAN level, the concept of node is transparent. One doesn't need to know where a message is coming from, it should just concentrate what the message is. Higher layer protocols do usually reserve a part of the CAN ID field to number the nodes in the network.

 

[vijay s]

@virtualThread
How can we identify a specific sensor in a CAN network?

please answer for this... i don't get anything on this

 

[microKernel]

I see that it's been answered by him. A sensor is a node.

Higher layer protocols do usually reserve a part of the CAN ID field to number the nodes in the network

so you can do that.

 

[gooofy871]

Each sensor in a CAN network can be called as a Node.. Each CAN node consist of a CAN ID (somthing like a IP address v have for our LAN network..) When a node want to communicate with another then the message that has to me communicated will be appended with the specific CAN ID and will be broadcasted in the network and according to the acceptence filter configuration the message will be read by any other node or will be discarded

 

[vijay s]

Is there a specific format to Transfer a message in CAN protocol or it is vendor dependent...

is there any spec abt Message encoding in CAN protocol...

 

[gooofy871]

CAN is a protocol made by bosch. its spec is avilable in google.. its a bit confusing to read that spec.. anyway if u read it a couple of times u will get some idea...!!!

 

[vijay s]

@gooofy871
i have read the Spec.. i have good idea on its protocol... all i want to know is how the Messages are encoded in CAN protocol... for Ex.. if i have to read Engine Temperature, how Temperature will be encoded with message...

 

[gooofy871]

If i am right r u confused how this transmission is happening?? I m attaching a sample code of a CAN transmitter and CAN receiver.. and also a CAN primer from Keil which explains how to create a CAN Network.. Hope this might help you..

 

[gooofy871]

I have PM'd you the CAN code.. its written for LPC2378.. Perfectly in working condition.. If any body wants the same code PM me..

 

[guptamanil]

Hi, I am also working on developing a CAN node using LCP2378. where can i get the source code from @goofy871

 

[microKernel]

Send gooofy871 a personal message by clicking PM button against his post.