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internal pullup resister — Parallax Forums

internal pullup resister

AHMET AKSUAHMET AKSU Posts: 62
edited 2007-09-25 15:13 in General Discussion
I m using this circuit for sensor reading.is it possible to use internal· pullup resistor of sx48 and not use 10k resistor on attachment

Post Edited (AHMET AKSU) : 9/25/2007 1:06:59 PM GMT
bmp
bmp
SENSOR.bmp
234K

Comments

  • BeanBean Posts: 8,129
    edited 2007-09-25 13:07
    Yes, the internal pull-ups function about the same as a 20K resistor when the supply is +5V.

    Bean.

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  • AHMET AKSUAHMET AKSU Posts: 62
    edited 2007-09-25 13:18
    thanks Bean.how can I use internal pullups in sx/b language
  • BeanBean Posts: 8,129
    edited 2007-09-25 14:32
    Sensor PIN RB.0 INPUT PULLUP

    Bean

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  • T&E EngineerT&E Engineer Posts: 1,396
    edited 2007-09-25 14:36
    I'm using a serial (Rx, Tx) display very similar to the uOLED 128 GMD1 that Parallax now distributes. The Basic Stamp Demo code (and Connection diagram) for the uOLED 128 GMD1 states that 10K pull up resistors should be tied high on the Rx and Tx lines.

    http://www.parallax.com/detail.asp?product_id=27925

    I would like to use my uLCD-320-PMD2 display with an SX-28 and it would be convient to use SX/B internal pull up coding·versus actual external 10K resistors.

    https://www.littlepcbsolutions.com/uLCD-320-PMD2.html

    Do you think this would be ok? Is there any test I can do to check to see if they are needed or can use the internal pull up coding?

    However, recently I saw on another posting that 4.7K resistors should be used on serial data lines like this.

    Comments?
  • BeanBean Posts: 8,129
    edited 2007-09-25 15:03
    The value of the pullup depends on what rise time is needed and the capacitance at the pin.
    The smaller value resistor, the more current is used when the line is pulled low, but the faster the rise time.
    On most things it doesn't really matter that much. 4.7K, 10K, 20K
    If you have problems with communication, try a lower value.

    Bean.

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    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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    ·
  • AHMET AKSUAHMET AKSU Posts: 62
    edited 2007-09-25 15:13
    thanks Bean.working
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