Last time I have made something like this it is ended up as a token ring :-) So the 1st PIC's TX goes to the 2nd RX, then it's TX to the 3rd RX and so on (and the two end is to the host/master of course). The host sends a message with an address, and if a PIC is not addressed then it just passes the message to the next PIC... Relatively easy to implement and it was fast enough to me. Regards, Tamas On Sat, Aug 23, 2008 at 1:13 PM, Jinx wrote: > Progressing with the network sensor project of a couple of weeks ago > > The set-up settled on is a group of up to 5 PIC-based analogue and > digital sensor units per network node. Each unit will have a unique ID > and they will respond to network requests directly when called or > separated in time according to their ID if called as a group. Either way > there would/should be no collisions > > A prototype with just one PIC unit has been installed remotely and tests > OK, reporting various voltages, switch states etc. Kind of cool reading > a battery voltage and temperature several miles away. I'm sure the novelty > will wear off > > Two questions - > > 1) how could MAX232's be paralleled ? > 2) I'd rather not use a transceiver IC if the job could be done with a few > transistors. I realise this will mean making a -ve voltage for data '1', > which > may have to be distributed too > > The background ...... and attached graphic > > Network interface to that PIC's Rx and Tx is via a MAX232. The next > step is to build a few more of these units and stack them up in parallel, > connected by a 4-way cable of 0V, 5V, Rx, and Tx, to a distance of a > few metres > > So all the MAX232 Rx are tied together, ie all the pin 8s or 13s. For > the Tx's I think I'd have to use at least one transistor to isolate the > MAX232 driver from the Tx line going back to the network. That's > assuming I stick with the MAX232, but I'd rather not if it can be done > a better way (cheaper, no unused transceivers) if possible > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > -- Rudonix DoubleSaver http://www.rudonix.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist