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Before the fun begins — Parallax Forums

Before the fun begins

El PaisaEl Paisa Posts: 375
edited 2006-05-02 18:02 in Propeller 1
I think this the time for Chip to give us guidelines of how to deal with the +5 modules when connected to the propeller.
I have some modules rated at 3.3 volts, some rated at 3.3 V but tolerant to 5V, some just plain 5V.

What procedure or protection do you recommend?.

I do not want to blow any Propeller and void the warranty.

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-05-02 02:07
    We've found the Propeller 5v tolerant, but you can put a 1K resistor between the Propeller I/O pin and a 5v device for a bit of insurance.

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    Jon Williams
    Applications Engineer, Parallax
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-05-02 03:06
    I have had trouble getting a MAX3232 [noparse][[/noparse]the 3.3v version] locally, so I am considering a dual voltage setup and using a MAX232 until one arrives.

    This is what I am thinking of doing.

    The TTL Rx between the MAX232 and the PROP would use a 1000 ohm resistor, right?
    The TTL Tx between the MAX232 and the PROP would use nothing, okay?
    The 3rd line which is a reset seems like I could leave it unchanged.

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    "When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-05-02 14:27
    Kramer,

    ·· If you have a few 2N3904 NPN transistors laying around, a 2N3906 PNP and a few resistors you can make your own serial interface per the schematic posted elsewhere in this forum.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-05-02 15:00
    Thanks Chris,
    That would be in the PropStick's thread.

    I was thinking that the voltages might be too low. But, it is a start.
    Mouser has backordered my purchase of MAX3232s in DIP for 5 weeks.

    I can only get SMDs from my alternative.


    So, it looks like the transistors are a bit simpler than a double power supply.

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    "When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

    Post Edited (Kramer) : 5/2/2006 3:40:36 PM GMT
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-05-02 15:24
    Kramer,

    Propeller Serial Programming Adapter - Testing

    http://forums.parallax.com/showthread.php?p=581171

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • SterlingSterling Posts: 51
    edited 2006-05-02 16:12
    So if I'm powering the Propeller with a PDB, I should use a 1K resistor, right?
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-05-02 18:02
    Remember that the Propeller is powered with 3.3v.· If you put the Propeller into the PDB breadboard you'll need to include a regulator circuit with it.· I've attached a picture of my PDB setup (running the timer demo).· Notice that you can use the BS1 connector for the USB2SER (upside down) -- just use a 22-gauge wire (purple in the pic) to connect USB2SER.RES\ to Propeller.RESn.

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    Jon Williams
    Applications Engineer, Parallax
    Propeller_on_PDB.jpg
    1024 x 768 - 378K
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