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Usage of pin 31/30 in design - recommendations/exeprience? — Parallax Forums

Usage of pin 31/30 in design - recommendations/exeprience?

Timothy D. SwieterTimothy D. Swieter Posts: 1,613
edited 2008-01-06 04:46 in Propeller 1
I am working through some design thoughts for a project.· I am considering the use of I/O lines 30 and 31 to attach to a peripheral.· During download to the Propeller, of course these lines are used as Tx/Rx.· What considerations should I think about to protect the pheripheral during download?· The pheripheral may be an SPI or I2C device.·

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Timothy D. Swieter
tdswieter.com
One little spark of imagination is all it takes for an idea to explode

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2008-01-06 04:44
    If it's an I2C device, why not just hang it off of pins 28 & 29? Peripheral devices have different addresses from EEPROMs and can easily co-exist on the same bus.

    -Phil
  • Mike GreenMike Green Posts: 23,101
    edited 2008-01-06 04:45
    Look at the Propeller Loader in Spin that Chip wrote and posted long ago. The PC (or Loader) sets up its I/O pins and sends some calibration pulses to the Propeller. I assume that, if the Propeller doesn't see these, that it gives up and stops itself. The Propeller will setup Pin 30 for output high and Pin 31 for input, then, once it gives up, will set Pin 30 back to input mode. As long as your SPI or I2C device will tolerate a logic high on one pin and a high impedance on the other pin, you should be fine. You could put the I2C or SPI clock on Pin 30 and the data on Pin 31. A pullup on pin 30 will keep the I2C or SPI device from reacting to the high output.
  • Timothy D. SwieterTimothy D. Swieter Posts: 1,613
    edited 2008-01-06 04:46
    Thanks Phil - I considered this and actually did this in another project where I had I2C. I am trying to gear my project for use with the uOLED-96-PROP which doesn't easily expose those pins plus my device may be SPI. I suppose little wires could be soldered to the EEPROM on the board to gain access.

    Good suggestion Mike.· I will review the datasheets for my potential devices to see what it says.

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    Timothy D. Swieter
    tdswieter.com
    One little spark of imagination is all it takes for an idea to explode
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