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