Using 1 wire for BMS communication bus

[Chris Ewert]

I looked into 1 wire a bit. It looks like a nice bus communication
system and it looks like it should work for what we need. From what I
gathered, its a bus with a single communication wire thats normally at
+5 volts. A bus master then pulls the comm line down on a set
interval. If another chip wants to communicate, it simply continues to
hold the line down for a certain amount of time beyond the clock to send
a 1 and a longer amount of time to send a 0. Its similar to serial, but
bi-directional. This would be nice because instead of 3 wires for
standard serial, it would only require 2 (comm line and bus ground.) See:
http://en.wikipedia.org/wiki/1-Wire#Example_communication_with_a_device

I believe we need something that is optically isolated at each board
since the boards are all sitting at different potentials. I'm trying to
figure out a way to optically isolate it where we can have 60-65 boards
on one bus. I uploaded a schematic of something, but it seems rather
precarious to me. Does anyone have experience with 1 wire or have a
better idea? Perhaps thats too many boards and we need to split them
into smaller buses? Or perhaps theres a way to do this without
opto-isolation?

The schematic of what I came up with for optically isolating the bus is at:
http://freebms.googlegroups.com/web/BUS_Idea_1_Wire.jpg

Chris