TCAN4550: CAN to RS-485 conversion

Hi Mark,

Yes, that would do it.  Or you could use an MCU with an internal CAN controller and use an external transceiver IC like TCAN1042-Q1.  Keep in mind that the interfaces work differently in terms of the data link layer.  CAN has a defined frame structure and supports ID-based arbitration of messages so that simultaneous transmissions from multiple nodes can be sequenced automatically in a priority order.  RS-485, on the other hand, doesn't have a defined data protocol (although simple UART start/stop bit encoding is common) and uses a physical layer that cannot directly support multi-master arbitration.  So, you would need to be thoughtful about how the data is packaged up between these two interfaces and how bus access is managed on the RS-485 side.

If you don't care about the data protocols and are just looking for direct physical layer conversion there may be a simpler solution bypassing an MCU in favor of some discrete logic.  Let me know if that is the case and we can give it some more thought.

Max

Hi Max,

Digging into this a little more, it looks like the interest is to do a direct physical layer conversion as you mention in your second paragraph. 

Any suggestions for this are appreciated. . 

Hi Max,

If the RS-485 bus is full duplex, could one get away with a simple interface such as using a THVD1451/52 RS-485 transceiver connected to a CAN transceiver like the TCAN1042HV?  Just interconnect the logic data lines (D to RXD, R to TXD). The RS 485 side would need to default to having R data high to keep the CAN bus in recessive mode when not sending data. 

Half duplex RS-485 would be more challenging since one would have to deal with the T/R control of the RS-485 bus and the switching times between the modes is probably too slow for CAN.