CANBUS and LINBUS Oscilloscope questions  - Page 1
Forum section: electronics / beginners

author: tommythrash
author_rank: Contributor
timestamp: October 20, 2013, 05:48:36 am
content: Hi, I am relatively new to more advanced electronics. I work for a mobility company that converts vehicles for people with disabilities. I specialize in hand controls. Some of these systems interface with the OEM accelerator. Other systems allow the user to control the secondary functions such as lights and wipers through a wireless remote on the steering wheel. My question is that some of these connections are made using a CAN or LINBUS signal. Also some accelerators use a PWM signal. I would like to buy an oscilloscope to identify these signals but am on a budget. I would like to find the best oscilloscope for this and if possible a built in decoder for CAN and LIN. If I cant get that built in for a reasonable price is there any way to build a decoder? Any help would be appreciated.

author: Rerouter
author_rank: Super Contributor
timestamp: October 20, 2013, 06:06:59 am
content: i work with RPM controllers and speed limiters in the automotive sector and short of 2 models of the latest fuso trucks, all trucks and cars (and forklifts) with an electronic throttle dont care if its a linear voltage or PWM, (the fuso's have an ac coupled data comms)as far as pedal signals go, short of a few odd chinese and one american car these signals have been run straight to the ECU and digitised there, for all of these a $10 multimeter will get you within spec, record the high point record the low point, and for older models record the IVS threshold, (range is linear)as for decoding CAN a scope may be the wrong approach, if you only care what is being transmitted rather than if it complies to the voltage and timing standards a logic analyser is a far better choice for when you are on a budget,hope this helps,

author: tommythrash
author_rank: Contributor
timestamp: October 20, 2013, 07:06:07 am
content: Thank you for the information on the logic analyzer. I just tried to read up on them but there are a lot of options. What Logic Analyzer would you suggest for my needs?

author: tszaboo
author_rank: Super Contributor
timestamp: October 20, 2013, 07:31:47 am
content: Or dedicated USB-CAN interface would be even better. CAN is a complicated messaging interface. You have 30 something bit just to describe an 8 byte message, and there will be a ton of different message, not all of them related to what you need. The good thing with these interfaces, that they come with a software, which is essential to decode the message. You can do it by hand, but it just takes too much time, and you wont be able to catch all message with a scope, and a logic analyzer is usually doesnt represent the data in a usable format.

author: tommythrash
author_rank: Contributor
timestamp: October 20, 2013, 07:45:35 am
content: Where can I read about your dedicated USB-CAN interface? I didn't see it on your blog. Also, will it work with other types like LIN?

author: tszaboo
author_rank: Super Contributor
timestamp: October 20, 2013, 08:25:50 am
content: Well, there are a lot of commercial product out there. Making a hardware for it is not a big deal, you can snap a working product together in a week. It all comes to the software.If you are really low on $$$, i would search for an open source tool. But you will spend a lot of time there. Since CAN is 80s technology, it is not a problem to make it work with DIY equipment.Otherwise buy something, and then it works out of the box. Kvaser makes good products, at least what I've used was good. They are worth the money, if you calculate in the price of your work.

author: tiofilo75
author_rank: Contributor
timestamp: October 20, 2013, 08:53:04 am
content: I am currently working with a group at school where we communicate with an electric vehicle's BMS through a CAN interface. We are using an Arduino Uno and a CAN shield like this:http://www.ebay.com/itm/SeeedStudio-SLD01105P-CAN-BUS-Shield-NEW-/330990124046?pt=Educational_Toys_US&hash=item4d108c7c0eIf you code it correctly you can see what you get when you make a request to the device. Keep in mind that you need to know what bytes you must sent to get the proper bytes back. Initially we used an Agilent 2000x oscilloscope with a trial version of CAN, which helped us see the signal and the requested and received bytes. After we verified that we were getting the correct data we came up with a list of PID that we sent out. From these we were able to calculate the voltage, temperature, etc... of the different cells in the vehicle. This worked like a charm for us so it might be the same with you.

author: tommythrash
author_rank: Contributor
timestamp: October 20, 2013, 11:17:18 pm
content: I am looking into logic analyzers. I do have a beaglebone black that has CAN on it. I have not found much about it but I would need something that can read a CAN and LIN, decode it and help me figure out what code is being sent over the network when I switch on the wipers, turn signals, lights, etc. I would like to build this myself, I have been looking for a usable project. I really like the Saleae logic, it looks durable and portable, it also shows that it supports CAN and LIN for under $150USD.

author: tommythrash
author_rank: Contributor
timestamp: October 21, 2013, 05:13:54 am
content: Ok, after doing some research I think for what I do the IKALogic ScanaPLUS might be the best option for me.http://www.ikalogic.com/ikalogic-products/scanaplus-9-channels-100mhz-logic-analyzer/It is portable and has built in 50vMAX protection. Has anyone seen or used this Logic Analyzer?

author: cwalex
author_rank: Frequent Contributor
timestamp: October 21, 2013, 12:30:06 pm
content: the logicport is more advanced and a solid product.http://www.pctestinstruments.com/I haven't used it with can but it supports can and you have 34channels of 500MHz to play with and nice software. $389. I haven't heard a bad word about it.

author: tszaboo
author_rank: Super Contributor
timestamp: October 22, 2013, 07:53:15 am
content: Quote from: tommythrash on October 20, 2013, 11:17:18 pmThe main problem with dedicated CAN devices, is that they will not detect for you if there was error, collision, acknowledge error or any type of misbehavior on the bus. They are fine, unless you start debugging, and then having trouble telling, why your product is not working after connecting it to CAN. If you have some analizer, it will tell you, really what is happening on the bus.

author: zapta
author_rank: Super Contributor
timestamp: November 11, 2013, 04:37:54 pm
content: Quote from: tommythrash on October 20, 2013, 11:17:18 pmebay has inexpensive Saleae compatible logic analyzers.

author: Kohanbash
author_rank: Regular Contributor
timestamp: November 11, 2013, 04:50:01 pm
content: It is a bit expensive but I use thehttp://www.phytools.com/PCAN_USB_Adapter_CAN_USB_Interface_IPEH_002021_p/ipeh-002021.htm?gclid=CNv_k7aX3boCFVRnOgodnVMAZgThey also have other CAN interfaces besides USB.It has a basic interface that lets me send, view, and log packets.When I am developing I use this to continuously snoop on the CAN bus.

author: garak
author_rank: Contributor
timestamp: November 12, 2013, 04:46:02 am
content: If you're on a real budget, and are only interested in the content of transmitted messages, you might also be able to make do with a USB-CAN bridge usually used for diagnostics or Carputer purposes. Ebay is full of devices based on the ELM327 for very little money indeed. They use a serial interface that ELM have documented fairly well, so writing a quick program to log the messages received would be child's play.