4 18m2 serialed quick questions

hi,

I have currently 2x 18m2 picaxes serialed toghther and comunicating perfectly. when i add the third or forth picaxe to from a kind of serial bus network. the reailabily goes down.

outputs are all the same pin serin, b.2
inputs are all c.2
all running t9600_16

one picaxe is a master the 3 others are slaves

would the serial line require pullup pulldown resistors or diodes of some sort?
 
another question,

what would be the ideal/best/max distance of serial comms?

i was thinking about using cat5e cable using 2 of the twisted pairs serial in/out and tying the other to ground to help with some kind of screening
 

Goeytex

Senior Member
Here's a circuit that incorporates a negative input diode "OR" and is for use with non-inverted serial (T9600_X). For use with inverted serial, reverse the diodes and make the resistor a pulldown instead of a pullup. The diodes prevent the outputs from shorting each other out if , for example one is high and another is low.

For the master to receive data reliably, only one slave can be transmitting at any given time.
 

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