Alexey Vladimirov wrote:
 >
 > 27 Jan 97, Craig Houston writes to All:
 >
 >  P> I was wondering if anyone out there had any information on
hooking up
 >  P> PICs in a network like structure.
 >
 >  P> My plan is to have a bunch of PICs controlling various things, at
 >  P> different locations throughout the house, and wanted to link them
all
 >  P> up - short of using a master PIC with all Tx / Rx lines from each
PIC
 >  P> going into it, I thought a network topology would be best.
 >
 > What speed is necessary for your application ? For low-speed
technology
 > (till 1200 baud) we made one interesting solution:
 >
 > All local controllers connected via 2-wire line and powered from the
same
 > wires. Controllers number depends from their supply current and
 > in most cases could be in range 50...500. Total wire length could be
up to
 > one kilometer (about 100 baud in this case). Total supply current for
all
 > controllers should not exceed 300...800 mA.
 >
 > System consist from one master controller and till 500 slave
controllers.
 > Master controller power all slave controllers and transfer data to
all
 > slave simultaneously by switching line polarity. Slave can transfer
answer
 > to master requests by short-time line shortenings.
>
 > We install some working netwoks, based on this technology in various
 >  applications: guard systems, home gas and water counters, sensor
networks, etc.
 >
 > I plan to made some kind of application note available in near
future.
 >
 > Alexey Vladimirov  avlad@mail.ormix.riga.lv
 >
 > http://www.ormix.riga.lv/eng/mchip/mchip.htm
 > more than 300 PIC-related Net resources now...
 >
 > --- GoldED/2 2.50+
 
 Did you check out CS212 from Cherry Semiconductors
 someone else also sugested this chip
 
 In brief it is designed to be used as slaves in a two wire
 loop 10-18 Volts, five address pins (up to 30 slaves per loop)
 
 Each slave has two digital inputs and two digital outputs
 data is transfered buy pulling the line to half voltage for 1
 and 0 Volts for 0
 
 A cap maintains power during data transmission
 spec's state that line requires max 20mA for 30 slaves
 
 Component count is very low (one cap, one diode and two resistors)
 
 It is designed for use in two wire alarm systems
 where inputs would be door contacts etc
 and outputs bells / door locks etc
 
 Maplin UK sell this chip for £5.50 in one's
 
     ---------------------------------------------------------------
 Peter Cousens
 email: peter@cousens.her.forthnet.gr
 snailmail: Peter Cousens, karteros, Heraklion, Crete, 75100, Greece,
 phone: + 3081 380534,    +3081 324450   voice/fax
 
 After Bill Gates announced to the world that he was Microsoft,
 his wife was asked to comment. She said that as his wife, she
 had been the first to notice this problem