halpxa27xbusywaitm.nc

tinyos2.0版本驱动

/*
 * Copyright (c) 2005 Arched Rock Corporation 
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/** 
 * This private component provides a 16-bit BusyWait interface
 * of a given precision over OS Timer channel 0
 *
 * @param precision_tag A type tag mapped to the set precision
 *
 * @param val4xScale A value to scale the underlying counter by. 
 *   The passed in parameter is given by the equation
 *   val4xScale = (3.25 MHz/<desired_precision_in_Hz>) * 4
 *   and rounded to the nearest integer.
 *   Example: Counter precision of 32.768 kHz would have 
 *   a val4xScale of 397
 * 
 * @author Phil Buonadonna
 *
 */

generic module HalPXA27xBusyWaitM(typedef precision_tag, uint16_t val4xScale)
{
  provides interface BusyWait<precision_tag,uint16_t>;
  uses interface HplPXA27xOSTimer as OST;
}

implementation
{

  async command void BusyWait.wait(uint16_t dt) {
    uint32_t dCounts;
    atomic {
      uint32_t t0 = call OST.getOSCR();
      dCounts = (dt * 4) * val4xScale;
      dCounts >>= 2;
      while (((call OST.getOSCR()) - t0) < dCounts);
    }
  }

  async event void OST.fired() {
    return;
  }

}