eeprom.c

旋转16个LED灯控制程序

/* Stripped to just what CharPOV needs */

/******************************************
SpokePOV V1.0 firmware

SpokePOV firmware is distributed under CC license. 
For more info on CC go to www.creativecommons.org
For more info on SpokePOV go to www.ladyada.net/make/spokepov

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******************************************/

#include <avr/io.h>
#include "eeprom.h"
#include "main.h"


// If we are not inline coding, define the spi_ routines as
// functions.  WARNING: make sure any changes in this code
// is also implemented in the macro version in eeprom.h!

#ifndef SPI_INLINE

// All of the following routines have been modified so they
// only deal with the front leds, for speed, and to save
// code space!

// Move n bits of data over the serial link

void spi_transfer_n(uint8_t c, uint8_t n) {

  // Stuff the byte to transfer into the serial data register
  
  USIDR = c;
  
  // Set up the status register.  On each state transition of
  // the serial bus (up or down), the lower 4 bits will be
  // incremented - so twice per bit.  When that overflows,
  // the transfer is done.  So if they start out as 0, 8
  // bits get moved.  But if you start it out at a different
  // value, you can move an arbitrary number of bits
  
  USISR = _BV(USIOIF) | (16 - (n<<1));

  // While the transfer has not finished
  
  while ( (USISR & _BV(USIOIF)) == 0) {

    // Send out another bit
    
    USICR = _BV(USIWM0) | _BV(USICS1) | _BV(USICLK) | _BV(USITC);
    //NOP;  // slow down so that the eeprom isnt overwhelmed

  }

}

// Move 4 bytes over the serial link (to the 1K/4K EEPROM or the
// LED shift registers, or both!).  This code does things "blind",
// clocking 16 times, to transfer the data as fast as possible.

void spi_transfer(uint8_t c) {

  USIDR = c;
  USISR = _BV(USIOIF);

  while ( (USISR & _BV(USIOIF)) == 0) {

    USICR = _BV(USIWM0) | _BV(USICS1) | _BV(USICLK) | _BV(USITC);
    //NOP;  // slow down so that the eeprom isnt overwhelmed

  }

  // The byte read, if any, will be in USIDR
  
}

void spieeprom_read(uint16_t addr, uint8_t *buff, uint8_t len) {
  uint8_t i;

  SPIEE_CS_PORT &= ~_BV(SPIEE_CS); // pull CS low
  NOP; NOP; NOP; NOP;

  spi_transfer(SPI_EEPROM_READ);           // send READ command
  spi_transfer(addr >> 8);                 // send high addr 
  spi_transfer(addr & 0xFF);               // send low addr

  for (i=0; i<len; i++)	{				   // read in the right number of
    spi_transfer(0);					   // bits, then move to buff[]
    buff[i] = USIDR;
  }

  SPIEE_CS_PORT |= _BV(SPIEE_CS);      // pull CS high
}

#endif