/* General support for SPI devices, but using bit banging and
using pin definitions rather than the built in spi functions in the microcontroller.

No specific initialisation is needed except port directions.


requires definitions of ATMEL ports:

	SPI_PORT		Port for the SPI signals eg PORTB
	SPI_DDR 		DDR for the SPI signals eg DDRB
	SPI_PIN 		Input Port for the SPI signals eg PINB

	SPI_SCK 		Clock from master to slave
	SPI_MOSI   		Data from Master to slave
	SPI_MISO   		Data from slave to master

SPI mode 0 where data to slave is latched on leading edge of SCK, and data
from slave to master is latched by master on fallling edge of SCK

Uses delay functions which require definition of F_CPU in config.h


*/

/* 23/2/2011  svn 282  */



#include <avr/io.h>
#include <config.h>
#include <spi.h>
#include <util/delay_basic.h>
#include <util/delay.h>


inline void spi_clock_up_down(void) {
	SPI_PORT |= (1<<SPI_SCK);
	_delay_us(2);
	SPI_PORT &= ~(1<<SPI_SCK);
}


uint8_t read_spi_byte(void) {

	uint8_t i;
	uint8_t bitresult;
	uint8_t result = 0;
	SPI_PORT &= ~(1<<SPI_SCK);
	for (i=0;i<8;i++) {
		_delay_us(1);
		bitresult = ((SPI_PIN >> SPI_MISO) & 0x01);
		result = (result << 1) | bitresult;
		spi_clock_up_down();
	}	
	return result;
}


uint16_t read_spi_2byte(void) {
	uint8_t i;
	uint8_t bitresult;
	uint16_t result = 0;
	SPI_PORT &= ~(1<<SPI_SCK);
	for (i=0;i<16;i++) {
		_delay_us(2);
		bitresult = ((SPI_PIN >> SPI_MISO) & 0x01);
		result = (result << 1) | bitresult;
		spi_clock_up_down();
	}	
	return result;
}


void write_spi_byte(uint8_t data) {

/* enter and leave with with SCK low */
	uint8_t bitpos;
	uint8_t bitvalue;
	SPI_PORT &= ~(1<<SPI_SCK);
	for (bitpos=8;bitpos>0;--bitpos) {
		bitvalue = ((data >> (bitpos-1)) & 0x01);
		if (bitvalue) {
			SPI_PORT |= 1<<SPI_MOSI;
		} else {
			SPI_PORT &= ~(1<<SPI_MOSI);
		}
		_delay_us(1); 
		spi_clock_up_down();
	}
}