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haveing a propeller chip communicate to a basic stamp 2 — Parallax Forums

haveing a propeller chip communicate to a basic stamp 2

sovsov Posts: 17
edited 2010-01-06 00:13 in Propeller 1
hello, I am a student that learns and uses parallax equipment. I am now building a security robot for my class and I have just about tried everything in tring to have a basic stamp 2 communicate to a propeller chip. First of all I know that the propeller chip uses 3.3v and the basic stamp2 uses 5v. I tried using a transistor to communicate between the two but it killed my propeller chip. Can anyone help me on this matter, or even display a circuit diagram if possible... thank you in advancesmile.gif

Comments

  • JonnyMacJonnyMac Posts: 9,208
    edited 2010-01-05 23:02
    If you use "open true" baud modes the the chips (Stamp and Propeller) only drive the line low, you use a pull-up (4.7K) to 3.3v; this is well past the input-high threshold of the Stamp and will work just fine. By using Open-True you can use one pin to talk back and forth.
  • MagIO2MagIO2 Posts: 2,243
    edited 2010-01-05 23:14
    How do you want to communicate? Serial interface?

    The 3,3V should be enough to be recognized as logical 1 on stamp-side. So, you could directly connect the propeller TX with the stamp.
    The 5V is not a problem on propeller side when you use a 10k resistor. Guess that's what's most times done when connecting the propeller to a keyboard which also has 5 V. So, connect the RX from the propeller to a 10k resistor.

    But you should be sure that you don't have bugs in the serial interface code, otherwise the next prop might learn to smoke ;o)

    I think the demo board schematic shows how to connect to a 5V keyboard. That's also a serial interface. It uses 4 resistors and seems to be a bit more bug-friendly.
  • kf4ixmkf4ixm Posts: 529
    edited 2010-01-05 23:24
    Sounds like they were starting to communicate,..... through smoke signals! jumpin.gif
    Sorry, no useful input here,but i couldn't help myself...smilewinkgrin.gif· We have all been there at one time or another.

    Post Edited (kf4ixm) : 1/5/2010 11:29:48 PM GMT
  • sovsov Posts: 17
    edited 2010-01-06 00:07
    the connection is a pin to pin connection, not serial
  • Mike GreenMike Green Posts: 23,101
    edited 2010-01-06 00:13
    A pin to pin connection is exactly what you need ... with a 2.2K resistor between the Propeller I/O pin and the Stamp I/O pin to protect against programming errors. You can use the Simple_Serial driver on the Propeller side and a SERIN / SEROUT statement on the Stamp side. It's more flexible if you allow for two I/O pins on each microprocessor so you have one channel going from the Prop to the Stamp and one going from Stamp to Prop, but you could use one I/O line with half duplex communications and decide which device (Prop or Stamp) is the "master" for communications purposes.
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