[Ovmsdev] Can I use a 2-wire canbus with a single-wire bus?

Craig Leres leres at xse.com
Tue Jul 2 05:16:21 HKT 2019

There aren't very many interesting can pids on the high speed (2-wire) 
can bus in my Cadillac. For example if I capture frames while using a 
tech2 to look at tpms data, nothing looks like tpms data. Since the 
tech2 has both 1 and 2 wire can interfaces I want to start looking at 
the low speed single wire bus. (Maybe it's just that a "little battery" 
car first sold in 2008 does things on the low speed bus that newer EVs 
do on a/the high-speed bus?)

My assumption is that the MCP2515 doesn't care about the physical layer 
as long as the speed is set correctly so my initial thought was to just 
back a 2-wire transceiver chip up to a single wire one, e.g. the MCP2515 
and MC33897. But a friend pointed me at a block post where this guy is 
using a 2-wire sparcfun shield to snoop a single wire bus:


He basically just ties can L to ground and can H to the bus. I also 
found a copy of the can single wire spec (J2411-2000) and it seems 
2-wire is 2V differential and single wire is 0-4V so I guess I see how 
this might possibly work (depending on how the bus i/o pins are designed).

Anyway, is it safe for me to do this with one of the SN65HVD233D 
transceivers used in the ovms V3 module?


More information about the OvmsDev mailing list