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dira[35] outa[35] wraps, I guess — Parallax Forums

dira[35] outa[35] wraps, I guess

CncjerryCncjerry Posts: 64
edited 2012-06-18 18:23 in Propeller 1
Man this one caused some problems. So on the quickstart board, there is a large header but I assume (without finding a schematic) that dira[35] and outa[35] actually effect dira[3] outa[3]. Is this as designed or a fluke?

I also read while debugging this that there are only 28 user pins available. So where are the other 4? I think I need more detail on the processor chip.

Thanks

Comments

  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-06-18 15:34
    They would certainly wrap, as only the bottom 5 bits are used to identify 32 I/O pins. As for why there are only 28 I/O pins, 0-27 are user-accessible, 28-29 are used for i2c to the boot flash, and 30-31 are used to connect to your development PC through the USB/Serial port.
  • Cluso99Cluso99 Posts: 18,069
    edited 2012-06-18 15:56
    Once the eeprom is loaded on P28/29 you are free to use those pins provided they can co-exist with the eeprom. P30/31 are also free to use provided you do not need to download code over these. These are the only pins that have any pre-ordained usage.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-06-18 16:15
    As Cluso99 said, you can use P28-P31 for other purposes once the Prop has been booted up. It can be a bit of a pain to use P28-P31 for other purposes.

    When demonstrated the Prop driving 32 servos, I had to add some switches to these pins so I could easily disconnect the servos during the boot or download process.
  • CncjerryCncjerry Posts: 64
    edited 2012-06-18 16:30
    so are you guys counting from 0? I am using pin 28, base 0 or the 29th pin and have been seeing a problem off and on, I wonder if that is the case?

    I plan to write to the eeprom for memory store and retrieve so I guess I should move things around.
  • kwinnkwinn Posts: 8,697
    edited 2012-06-18 16:37
    Yep, addressing starts at 0 for pin and memory addresses.
  • AribaAriba Posts: 2,690
    edited 2012-06-18 18:13
    Cncjerry wrote: »
    ..... (without finding a schematic)....

    It's a bit dangerous to connect components to a connector without knowing the pinout. And yes it will also be a very good idea to read more about the propeller chip first...
    Here you find the schematic for the Quickstart board and the layout of the expansion connector:
    http://www.parallaxsemiconductor.com/sites/default/files/parallax/P8X32AQuickStartSchematicRevA_2.pdf

    Andy
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-06-18 18:23
    There is nothing to prevent you from attempting to do things to any pin at anytime.
    OK, bad stuff might happen, but you can still do it. %^(
    Trust me, I've tried it. No damage to the chip, just my pride.

    Duane J
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