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Interfacing with a 16V logic bus TX/RX on a Prop — Parallax Forums

Interfacing with a 16V logic bus TX/RX on a Prop

mumcs01mumcs01 Posts: 3
edited 2012-04-01 22:48 in Propeller 1
This is probably more of a general electronics question, but I'm trying to interface this to a Propeller because I want to send and receive randomly on a bus and using seperate COGS is perfect.

I'm trying to connect to a bus with a prop using 2 pins 1 TX and one RX, the bus uses 0V +-4.5VDC for Low and 16V +- 6.5VDC for high and uses manchester incoding at around 1200bps. Anyone have any great ideas on the interface side to accompish this. TX/RX with a minimal set of parts. Ideally I was just going to use a dual channel Opto to do the level shifting, but I can't seem to find one that is tolerant in the 16 +-6.5V range. Any ideas should be great. Thanks!

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2012-04-01 09:47
    How about a simple voltage divider feeding a 5V tolerant Schmitt-trigger buffer with a 3.3V power supply? A roughly 1/5 divider, say with a 1K and 3.9K resistor in series should work. Worse case, the low voltage across the 1K resistor would be 0.9 or less and the high voltage across the 1K resistor would be 1.9V or more. The highest high voltage across the 1K resistor would be 4.6V. Here's one Schmitt-trigger buffer that would work.

    On the transmit side, you'll need a source of 16V. Just use an NPN switching transistor with a pullup to 16V.
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2012-04-01 22:48
    You have a very strange way of describing the DALI bus which would not be a general electronics questions at all unless it has nothing to do with a Propeller chip.
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