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Is it true the propeller can only access 8 of it's bits on the propeller board? — Parallax Forums

Is it true the propeller can only access 8 of it's bits on the propeller board?

MovieMakerMovieMaker Posts: 502
edited 2008-08-12 16:07 in Propeller 1
Is it true the propeller can only access 8 of it's I/O Ports on the propeller board? I read this somewhere. Or, does it mean the proto board can only access 8 without further circuits added? Do I need a servo card or can I just add a serial resistor to drive the motors on the boebot?

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-08-12 04:23
    The Demo Board only provides 8 I/O pins for arbitrary use. All of the others are accounted for (VGA / TV / Audio Out / Audio In / Keyboard / Mouse).

    The Protoboard has access to all the Propeller I/O pins although some of them are pre-wired for VGA / Keyboard / Mouse.
  • MovieMakerMovieMaker Posts: 502
    edited 2008-08-12 13:48
    Does this mean it can only control 8 devices ie; servo motors, etc. ??? I planned to add many many devices.
  • Robot FreakRobot Freak Posts: 168
    edited 2008-08-12 13:59
    If you are planning to add devices like VGA / TV / Audio Out / Audio In / Keyboard / Mouse, the Demo Board has nice connectors for them and you can use the 8 I/O pins left for things like Ping))) and Compass(uses 3 I/O).

    However, if you would connect more things that are not TV / Audio Out / Audio In, then you need direct access to the I/O pins and the Proto Board would be ideal.
    You can then use the Accessory Kit to attach VGA / Keyboard / Mouse.
  • hippyhippy Posts: 1,981
    edited 2008-08-12 14:14
    There are many ways to extend I/O to control multiple devices beyond the number of pins a Propeller Chip has. What's best depends on what you'll actually be doing. The best way to control an 8 digit 7-segment display won't likely be the same as controlling 35 relays or servos for examples.
  • Mike GreenMike Green Posts: 23,101
    edited 2008-08-12 14:38
    The Propeller also works very nicely with a variety of external I/O extenders. The 74HC595 is cheap and provides 8 bits per added device, is cascadable and uses only 4 I/O pins itself. There are quite a few I2C-based I/O extenders like the NXP PCA9554, Maxim MAX6956, or Microchip MCP23017. These have the advantage that they can be attached to the same I/O pins as the EEPROM.
  • jazzedjazzed Posts: 11,803
    edited 2008-08-12 16:07
    MovieMaker, you have a Propeller Protoboard right? You should be able use practically all unconnected Propeller IO pins (and some that are connected). Switching pin states is done via a 32 bit register, so you would be able to force all pins to either 3.3V or 0V except pin 31.

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