lbenson
Senior Member
I've read that multi-drop serial in RS232 form is only available (without adding complexity), with master to multiple slaves, but no response from slaves to master.
I've also read that for TTL serial (0-5V) this can be overcome by making each slave TX high-impedence except when it is transmitting.
Assuming very little traffic (one 2-byte message per hour might be a high average for 1 master and 8 slaves), and no concern about collisions if they did occur, would this work?
One picaxe-X2 master sending on a single wire to 8 14M2s with background serial receive (2-byte buffer), and the 8 sending on their TX only if they see that the TX line is not high (TRUE idle--someone else using it) and then immediately making that pin an input (high impedence). The picaxe-X2 master would hve RX on background serial receive into the scratchpad.
I don't want to look into wireless or RS485, and for distances, would be mindful of the recent thread by Jeremy Harris regarding termination: http://www.picaxeforum.co.uk/showthread.php?29589
Regarding Jeremy's thread, HIGH termination would obviate the test for HIGH to determine if another slave is transmitting.
What problems could be anticipated with this approach? Assume total distance of 15 meters.
I've also read that for TTL serial (0-5V) this can be overcome by making each slave TX high-impedence except when it is transmitting.
Assuming very little traffic (one 2-byte message per hour might be a high average for 1 master and 8 slaves), and no concern about collisions if they did occur, would this work?
One picaxe-X2 master sending on a single wire to 8 14M2s with background serial receive (2-byte buffer), and the 8 sending on their TX only if they see that the TX line is not high (TRUE idle--someone else using it) and then immediately making that pin an input (high impedence). The picaxe-X2 master would hve RX on background serial receive into the scratchpad.
I don't want to look into wireless or RS485, and for distances, would be mindful of the recent thread by Jeremy Harris regarding termination: http://www.picaxeforum.co.uk/showthread.php?29589
Regarding Jeremy's thread, HIGH termination would obviate the test for HIGH to determine if another slave is transmitting.
What problems could be anticipated with this approach? Assume total distance of 15 meters.