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Interfacing Propeller Chip — Parallax Forums

Interfacing Propeller Chip

James LongJames Long Posts: 1,181
edited 2006-08-26 00:26 in Propeller 1
Ok guys.....I did have a bunch of manuals about ic interfacing and such.....but I don't have them any more.

I have a bunch of interfacing to do. Multiple Serial communications.....also some 5 volt two way communication, and some adc type things.

I have found some Maxim IC's for the ADC's. I have also found some R232 translators for the right voltage.

Now the real question....what about two way 5 volt single pin communication?

The voltage thing is really throwing me for a loop.

James

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2006-08-25 20:42
    What do you mean by 5V single pin communication? I'm imagining an open-collector/open-drain party line with a pullup to 5V. Is that what you mean? Philips has some nice simple circuitry for connecting a 3.3V I2C bus to a 5V I2C bus bidirectionally. It's in their I2C specification. I've attached a schematic. The resistors could be anything from 2.2K to 10K depending on the number of loads and the distances involved.

    The I2C bus is really a single pin communication system with a clock added for synchronization so any bus extenders designed for I2C should work in this setting. The advantage of using active level shifting vs. just some protective resistors is that the Propeller might have trouble pulling the party line voltage low enough with the protective series resistor you'd need.
    i2c level shifting.jpg
    875 x 383 - 66K
  • HarleyHarley Posts: 997
    edited 2006-08-25 20:48
    James,

    See the second subject on interfacing on this forum started by Dave Scanlan. This covers probably most of the 3.3v vs 5v interfacing situations.

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    Harley Shanko
    h.a.s. designn
  • John AbshierJohn Abshier Posts: 1,116
    edited 2006-08-25 21:34
    What device is TR1/TR2?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-08-25 21:40
    John,

    ·· It looks like a specialized FET of some sort.· It's a FET, but the diode must be something used in this configuration for control/connecting two different voltages?

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Mike GreenMike Green Posts: 23,101
    edited 2006-08-25 22:00
    Look at the discussion later in the "sticky" thread on 5V interfacing. They mention several FETs that can be used. The diode is the built-in one for inductive loads. Philips does use it in this scheme. They discuss it fully in their I2C Specification which is attached to one of the messages in the "sticky" thread.
  • James LongJames Long Posts: 1,181
    edited 2006-08-26 00:26
    Ok....so I feel stupid now....I haven't noticed the sticky thread.....



    Thanks guys....this is a huge project for me...I think I will end up with two propellers to make the project work.



    James
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