I need to receive CAN BUS in a Fiat Ducato. This car uses a Low-Speed CAN Bus for information about the state of door locks. The key voltage difference is that Low-Speed CAN (LS-CAN) operates with a larger differential voltage (up to 4V), while High-Speed CAN (HS-CAN) uses a smaller differential voltage (around 2V) during the dominant state.
Can the CAN Bus Breakout Board help me with this task? Or is it only capable of vHigh-Speed CAN Bus?
Best Regards
Maettu
Yep, I read the Wiki more than just once, but I did not find any information about Low Speed Can Bus in particular, but perhaps I missed something? I could, of course, simply buy a board and try it out, but I fear damaging the cars canbus…
Hello Christopher
Thank you for the Product suggestions. I looked at them, but none of them claims to be able to read LOW-Speed CAN Bus Messages. Is this feature so unimportant that nobody cares, or does it work with any of these products anyway, so all my worries are unnecessary?
Do you expect theses products to work on a LOW-SPEED CAN Bus, or are your posts more like “have a look at these, maybe these are interesting for you”?
Best Regards
Matthias
Hi there,
From what I get it’s just the baud rate mostly, and the connections all use the same transceivers so the physical connection is standard.
" Low-Speed CAN is commonly used to control “comfort” devices in an automobile, such as seat adjustment, mirror adjustment, and door locking . It differs from High-Speed CAN in that the maximum baud rate is 125K and it utilizes CAN transceivers that offer fault-tolerant capability. "
from NI site I know the basic seeed unit can be used to monitor the bus and see what frames for codes is possible.
NI say’s
"Low-Speed CAN is commonly used to control “comfort” devices in an automobile, such as seat adjustment, mirror adjustment, and door locking. It differs from High-Speed CAN in that the maximum baud rate is 125K and it utilizes CAN transceivers that offer fault-tolerant capability. This enables the CAN bus to keep operating even if one of the wires is cut or short-circuited because it operates on relative changes in voltage, and thus provides a much higher level of safety. The transceiver solves many common and frequent wiring problems such as poor connectors, and also overcomes short circuits of either transmission wire to ground or battery voltage, or the other transmission wire. The transceiver resolves the fault situation without involvement of external hardware or software. On the detection of a fault, the transceiver switches to a one wire transmission mode and automatically switches back to differential mode if the fault is removed.
Special resistors are added to the circuitry for the proper operation of the fault-tolerant transceiver. The values of the resistors depend on the number of nodes and the resistance values per node. For guidelines on selecting the resistor, refer to Cabling Requirements for Low-Speed/Fault-Tolerant CAN.
plus the adapter for OBDII connection. All in all how bad do you want it is the question.
the software it comes with is pretty good I’m told it does what is needed in most cases.
YMMV
HTH
GL 
PJ 
all the how to’s start with monitor the mirrors for the code to move them…LOL
Yes… I have never tried to use can so I don’t know… I know that some people may not know all the products which have been produced by seeed and sometime they do not come up I search results so I just sent them:… I didn’t go thru the data to see how f it had such a mode
Hi,
Low-Speed CAN and High-Speed CAN are not compatible because they are different in physical definition, just as you mentioned.
https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019LzHSAU
@maettu Unfortunately in German, but the following page may describe exactly what you’re interested in: Smart Camper – Fiat Ducato Komfort CAN Bus
@Seeed_Harrison gave the only informed answer and all others didn’t even understand the intent of the orginal posted question.
Summary about the Seeed Xiao CAN bus expansion board: this can only handle high-speed CAN. The used PHY (SN65HVD230) is limited to that only which can be verified easily by reading the introduction of the datasheet that states “compatible with ISO 11898-2 standard”.
In case you want support for low-speed CAN of ISO 11898-3 signals you need to explicitly search for PHYs that support it (e.g. TJA1055 by NXP). There may be some available that support both low- and high-speed of ISO 11898-3, but I haven’t seen any so far.
Hi there,
And welcome here, So even though you also didn’t provide a solution I do appreciate the contribution to the discussion, Your opinion however as to what is understood by others ASSUMES a lot, IMO an answer
would be more like the one, NXP support provided to a similar question:
Have you considered using the TJA1055T: Fault-Tolerant CAN Transceiver?
The TJA1055 is the interface between the protocol controller and the physical bus wires in a Controller Area Network (CAN). It is primarily intended for low-speed applications of up to 125 kBd in passenger cars.
No shade just a source…
As you were…
HTH
GL PJ
Here is a diagram of what the op was trying to achieve, they make 5v and 3v Xiao compatible silicon.
@PJ_Glasso:
I don’t see where I didn’t provide a solution. The link to the German blog page provides a full solution exactly as the thread-owner needs it:
I even had some doubts initially to post that answer as the thread-owner and blogger both share the same first name and might have been the same person. However, the German page shows a lot deeper understanding of the problem and solves all issues including selection of the right PHY chip TJA1055T/3 of which he claims (in the comments) that after he had finished his project still has a few left over to share (something the thread-owner would clearly not).
Worth noting, that blog page also tells how to hack connecting to low-speed CAN with a high-speed PHY (thanks to the fault-tolerant design and getting along without a full ISO 11898-3 compliant PHY), if the application needs only read access to CAN (see thread-owners intent). And it shows how to pivot-select the right CAN messages, which the thread-owner doesn’t need anymore as the vehicle-specific ID coding is presented on that blog page as well.
About my “harsh” assumptions: I’m only impressed about 10 answers being posted with not providing any solution close to the thread-owners original intent and this being a deep tech-centric forum. The 11th answer at least details what low-speed CAN means and refers to some web pages with limiting details (missing are e.g. fault-tolarance schemes, voltage levels, termination per wire and node, etc.). In contrast, a simple web search for “fiat ducato low speed can” finds the cited blog page. I made up the search terms now as I knew the blog post already for a while.
Best regards,
Stephan
Ok, I see,
Fair enough…
Thank you for the contribution, we are are all trying to stimulate the discussion and those that know more will share what they know about it, I get it is a very Niche’ area of can buss and the ISO spec. and more than likely not well know let alone understood.
Maybe seeed will update there hardware selection to include a LOW-Speed NFT version. 
GL PJ
