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RS232 connection? — Parallax Forums

RS232 connection?

QuadrtrFlyrQuadrtrFlyr Posts: 73
edited 2012-06-04 17:32 in Propeller 1
Hello folks,

I'm looking to hook up my propeller via RS232 cable. I have one wiring diagram I found here http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/PropellerDemoBd-RevG-Schem.pdf on the Propeller demo board.
But I am not sure if all the connections show there are necessary. I am just looking to communicate via RX/TX and am unsure of the wiring and hardware needed (resistors etc.)

Thanks a bunch!
Robert

Comments

  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-06-01 15:42
    What Propeller board to you plan to use?

    Are you making it yourself?

    If you use a board such as the Demo Board, you can use the USB connection to communicate with a PC.

    The Propeller datasheet has a schematic showing how to make a RS232 connection using some transistors and other components.

    An easier way to make the connection (RS232) is to use a MAX3232 chip.

    I'd be surprised if you really need an RS232 connection, since most PCs have USB ports and it would be just as easy to use it for Prop to PC communication.
  • QuadrtrFlyrQuadrtrFlyr Posts: 73
    edited 2012-06-01 15:49
    Thanks Duane,

    In my case I definitely need an RS232 connection and it cannot be USB. I am communicating via a Target PC in Matlab which only supports RS232.
    I am currently using the basic Propeller 40 pin chip that comes in the education kit.
    I found the schematic in the datasheet and I will most likely use that. What is the benefit of using the MAX3232 chip? Do you have a schematic?

    Robert
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-06-01 16:06
    I've used these chips myself.

    The schematic on the webpage uses 1uF caps. I believe the schematic in the datasheet uses 0.1uF capacitors.

    I've used these chips with 0.1uF capacitors successfully in my Propeller projects for several years.
  • QuadrtrFlyrQuadrtrFlyr Posts: 73
    edited 2012-06-01 16:14
    Alright great thank you! I have 0.1uF caps poly and mono radial. Which one should I use? Also I have a 15 pin connector, Is this the right diagram with
    equal pinouts? http://www.aggsoft.com/rs232-pinout-cable/modem-db9-to-db15.htm

    Thanks
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-06-01 20:13
    QuadrtrFlyr wrote: »
    Alright great thank you! I have 0.1uF caps poly and mono radial. Which one should I use? Also I have a 15 pin connector, Is this the right diagram with
    equal pinouts? http://www.aggsoft.com/rs232-pinout-cable/modem-db9-to-db15.htm

    Thanks

    I've always use ceramic capacitors with the RS232 chips. I don't remember it the datasheet states which kind to use.

    I like to use the little 0603 smt caps since they fit between the pins of the chip.

    I've only used 9-pin connectors with my serial connections. I'm not familiar with the wiring of a 15-connector. Maybe someone else here has experience with 15-pin serial connections.
  • Cluso99Cluso99 Posts: 18,069
    edited 2012-06-01 20:26
    RS232 only uses DB9 or DB25. The DB15 is most likely a VGA connector (3 rows of pins).
    The MAX3232 is fine with 0.1uF monos.
  • QuadrtrFlyrQuadrtrFlyr Posts: 73
    edited 2012-06-04 17:32
    Thanks folks!
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