Shop OBEX P1 Docs P2 Docs Learn Events
TTL vs RS232 — Parallax Forums

TTL vs RS232

172heavy172heavy Posts: 55
edited 2010-09-26 16:36 in Propeller 1
If I want to communicate with the prop using serial communication (fullduplexserialplus) without going through pins 31/30, do I need to build the circuit which converts ttl to rs232? This is assuming that I am communicating with a terminal program via a 9 pin serial port on my laptop.

Comments

  • localrogerlocalroger Posts: 3,452
    edited 2010-09-25 12:50
    It depends on your computer. You need a series resistor on the PC TX line and Prop receiving from the PC will probably work OK. (I use a 10K resistor for this.) Whether your PC serial port will receive from the Prop depends on the design of its input; some will accept 0-3v3 instead of the full swing, some won't.
  • 172heavy172heavy Posts: 55
    edited 2010-09-25 12:54
    localroger wrote: »
    It depends on your computer. You need a series resistor on the PC TX line and Prop receiving from the PC will probably work OK. (I use a 10K resistor for this.) Whether your PC serial port will receive from the Prop depends on the design of its input; some will accept 0-3v3 instead of the full swing, some won't.


    That makes sense I don't think mine will, my laptop will read and display the nmea strings in ht with no problem but if I send the exact same data from the prop...... No dice.

    Thanks
  • Mike GreenMike Green Posts: 23,101
    edited 2010-09-25 13:43
    In that case, you will need a voltage level translator. A MAX3232 should work. Follow the recommended hookup described in the datasheet for the device. You can also try the 3-transistor interface shown on the Propeller Downloads webpage. Just leave out the stuff connected to the /RES pin which is only needed for programming.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-09-25 13:55
    Don't forget that, if you're going directly from the Prop to a PC, you need to specify inverted mode for FullDuplexSerial.

    -Phil
  • localrogerlocalroger Posts: 3,452
    edited 2010-09-25 19:28
    THIS. Before you give up see if you at least have garbage in Hyperterminal. Garbage means your parameters are wrong, which can be fixed in software; nothing at all means you need to redo the hardware.
  • Heater.Heater. Posts: 21,230
    edited 2010-09-25 22:43
    Localroger:
    THIS.

    I have to ask, what is "THIS."?

    In recent months I've seen many posts on another forum that start with a that single word sentence, although not all in upper case. Now I see it here. I can't work out what it is supposed to mean.

    Is it just a mistake? Or is it YABA?
  • localrogerlocalroger Posts: 3,452
    edited 2010-09-26 06:49
    Heater, that particular usage of THIS generally means enthusiastic agreement with a previous post. It is a bit sloppy not to point out which one.
  • Heater.Heater. Posts: 21,230
    edited 2010-09-26 07:20
    localroger,

    This. How bizarre. Soon I won't even understand my native language:)
  • LeonLeon Posts: 7,620
    edited 2010-09-26 07:50
    Wouldn't THAT be more appropriate, since it refers to another post?
  • Heater.Heater. Posts: 21,230
    edited 2010-09-26 07:52
    THERE. It's not just me whose confused:)
  • 172heavy172heavy Posts: 55
    edited 2010-09-26 08:16
    OK, so I could not find a MAX3232 yesterday so I went with the parralax "prop to serial" schematic and it worked, also I had to invert the rx bits so now it works! I appreciate all of your help and just wanted to post my solution for the next newbie who runs into this problem..........

    now to master float math.......
  • localrogerlocalroger Posts: 3,452
    edited 2010-09-26 15:56
    I think the usage of THIS started out as the first thing you'd type in your own response after a blockquote, then people got out of the habit of quoting on boards where the source would usually be just above, and in some places you see it sort of randomly as I used it here, which looking back was not very clear at all. LOL @ net convs :-)
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-09-26 16:36
    Perhaps the rather quaint English "QUITE" would be a better choice for agreeing with what came before, saving "THIS:" (with the colon) to emphasize something one might say in a sentence that follows. In fact, that's how I thought it was being used in this context, despite being followed by a period and not a colon.

    -Phil
Sign In or Register to comment.