Shop OBEX P1 Docs P2 Docs Learn Events
Interfacing 3-Volt Device to Stamp2 — Parallax Forums

Interfacing 3-Volt Device to Stamp2

MikerocontrollerMikerocontroller Posts: 310
edited 2010-01-14 00:29 in BASIC Stamp
· I'm planning on interfacing a 3-volt FM chip to the Basic Stamp2.· I suppose I should take the 5 volt requlated Stamp output and feed it into a 3-volt voltage requlator.· That takes care of the supply.· How about interfacing the logic levels?· I'll be using a 3 wire SPI interface.· Do I need a level shifter chip or can I use discrete components?·· Better yet, a·low parts count·solution·for both power supply and level conversion?

Comments

  • Beau SchwabeBeau Schwabe Posts: 6,560
    edited 2010-01-12 03:48
    Mikerocontroller,

    How much current does the 3-volt FM chip require?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • MikerocontrollerMikerocontroller Posts: 310
    edited 2010-01-12 03:55
    Typical 14 mA. Maximum 16 mA.
  • FranklinFranklin Posts: 4,747
    edited 2010-01-12 16:06
    It depends on the chip. Some chips are 5v tolerant and can be connected directly or better yet with a resistor in series. Others need no more than 3v and you will need level shifters. You could make a resistor voltage devider or get something like the level shifter that another company sells (sfe) Also if you go to the propeller forum you will see in the stickys a discussion on connecting 5v sensors to the 3.3v prop.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • Spiral_72Spiral_72 Posts: 791
    edited 2010-01-12 17:56
    You could use a switching transistor.... what two resistors, a diode and a 2N2222A or similar transistor. The parts count would be minimal, a V regulator for the power..... One trip to Radio Shack would do it.

    An optoisolator would work as well.... both depending on your data speed.
  • Beau SchwabeBeau Schwabe Posts: 6,560
    edited 2010-01-13 06:59
    Mikerocontroller,

    If you want to use discrete components, they're small enough and available in SMT, might even be some IC transistor packages that would save some space as well.

    Anyway, there are two circuits here, one is a 3.3V transistor voltage follower that functions as a voltage regulator that uses a regulated 5V input as it's reference via a voltage divider. The 3.3V output should be good to at least 100mA. The other circuit functions as a bi-directional voltage level shifter. At any given time at least one side (the receiving side) of the level shifter should be made an input.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
    TRS.JPG
    552 x 840 - 146K
    TRS.JPG 146.5K
  • MikerocontrollerMikerocontroller Posts: 310
    edited 2010-01-14 00:29
    Thank you for the replies.
Sign In or Register to comment.