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STamp without echo? — Parallax Forums

STamp without echo?

tmacktmack Posts: 8
edited 2006-09-17 07:23 in BASIC Stamp
·Is there a way the stamp2 can be used without the echo? I want to use a rf remote but it is not a transciever.·There wont be a way for the stamp to·send the echo back. Is there a way to make this happen?· Kind of bypass the ech part? Or am I talking nonsense ? I·am trying ·is to use the Scribbler Gui to wirelessly control the scribbler.Thanks for any help

Comments

  • Tom WalkerTom Walker Posts: 509
    edited 2006-09-15 15:04
    The echo shouldn't hurt the process you have described. The Stamp does not care if the echo "goes" anywhere. If there was something on the other end receiving the Stamp's signals, then whatever it was would have to ignore the echo.

    In truth, the echo is an artifact of the hardware setup and not something that the Stamp actively "does" (i.e. not in the programming).

    HTH

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  • WeedogtWeedogt Posts: 6
    edited 2006-09-16 19:39
    I have the same question as tmack! The echo is really very troublesome in my application and I want to turn it of. I haven't found a software way to do so. I have a Basic Stamp 2sx.

    I had a look at the 2sx schematic; There's a 4.7 kOhm between Sin and Sout. Is this the "artifact of the hardware setup" that Tom Walker is talking about. How about removing that resistor (or connecting the Sin side to ground)?

    Why isn't there a real RS-232 driver/reciever chip on the Stamp, anyway?
  • allanlane5allanlane5 Posts: 3,815
    edited 2006-09-16 20:38
    1. RS-232 communications doesn't happen at 0 to 5 volts -- it's a +- 10 volt signalling level.

    2. The BS2 doesn't HAVE a +10 volt supply, nor a -10 volt supply. This keeps things simple.

    3. The BS2 uses two transistors, to use the TX voltage coming from the PC when it sends data back on the RX line.

    4. This is very clever and simple and space effective, and removes the need for THREE supplies, or an additional MAX-232 chip, which didn't exist when the BS2 was created.

    5. One side effect of this approach is that everything sent on the TX line ALSO appears on the RX line. On the one hand, this is a pain. On the other hand, this does validate that at least the BS2 'front end' hardware DID get what you sent, because you see the echo.

    6. If it REALLY bothers you, you can spend a little more for the RS-232 AppMod, which DOES have a built-in MAX-232 chip to handle the level shifting.

    7. Once upon a time (1990 or so) in order to program ANY programmable circuit, you had to purchase a $300 to $500 to $1500 'burner' for that purpose. The BS2's approach lets you program with merely a serial port.

    8. Anyway, that's why there isn't a "real" RS-232 driver and reciever on the Stamp. Note quite a few PIC chips now allow you to program them with a 'serial boot loader', but even in those circumstances you're going to need a SEPARATE RS-232 driver/reciever level shifter.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-09-17 02:05
    Bear in mind that if you disabled Echo (difficult) you will be unable to program the BASIC Stamp module.· However, if you use standard I/O pins and a line driver (such as a MAX232) you will not get echo.· Echo only occurs from the programming port.

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    Chris Savage
    Parallax Tech Support
  • hijkerhijker Posts: 10
    edited 2006-09-17 07:23
    I had the same problem and I removed the 4.7K resistor between pins 1 and 2.
    This solved the problem.
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