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kxp74.h
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kxp74.h
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/*****************************************************************************
* kxp74.h
* Lab 6: Final Project
* ECE 476: Digital Systems Design Using Microcontrollers
* Cornell University
* April 2007
* Andrew Godbehere (abg34) and Nathan Ward (njw23)
****************************************************************************/
/****************************************************************************/
//Include
#ifndef _KXP74_INCLUDED_
#define _KXP74_INCLUDED_
#endif
#include <spi.h>
#include <delay.h>
//SPI Chip Select (CS)
#define DDR_SENSOR1_CS DDRC.4
#define SENSOR1_CS PORTC.4
#define DDR_SENSOR2_CS DDRC.5
#define SENSOR2_CS PORTC.5
#define DDR_SENSOR3_CS DDRC.6
#define SENSOR3_CS PORTC.6
#define DDR_SENSOR4_CS DDRC.7
#define SENSOR4_CS PORTC.7
//KXP74 SPI Commands
//The accelerometer uses an 8-bit command register to carry out its functions
#define CONVERT_XAXIS 0x00
#define CONVERT_ZAXIS 0x01
#define CONVERT_YAXIS 0x02
#define READ_REGISTER 0x03
#define WRITE_REGISTER 0x04
//Operational Modes
//The 8-bit read/write control register selects the various operational modes
// Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
// 0 0 0 Speed_0 Speed_1 Enable Self test Parity
#define DEFAULT_MODE 0b00100 //Enable and set to 32KHz low noise mode
#define STANDBY_MODE 0b00000
#define SELF_TEST 0b00110
/****************************************************************************/
void init_sensor_spi(void) {
//Set SPI chip select data direction
DDR_SENSOR1_CS = 1;
DDR_SENSOR2_CS = 1;
DDR_SENSOR3_CS = 1;
DDR_SENSOR4_CS = 1;
//Initialize chip select signals high
SENSOR1_CS = 1;
SENSOR2_CS = 1;
SENSOR3_CS = 1;
SENSOR4_CS = 1;
}
/****************************************************************************/
void set_sensor_clock(void) {
//Set the clock polarity and phase for the accelerometers if other slaves
//(with different clock settings) are also being used by the MCU
SPCR0 = 0b01011101;
SPSR0 = 0;
//SPCR0 &= 0b11110111;
//SPCR0 &= 0b11111011;
}
/****************************************************************************/
void init_sensors(void) {
//Upon power up, the Master must write the operational mode command to
//each accelerometer's 8-bit control register.
unsigned char junk = 0;
//Sensor 1
SENSOR1_CS = 0; //CS low to select sensor 1 and start transmission
//On the falling edge of CS, 2-byte command written to control register
junk = spi(WRITE_REGISTER); //Initiate write to the control register
junk = spi(DEFAULT_MODE); //Set enable bit in the register
SENSOR1_CS = 1; //CS goes high at the end of transmission
//Sensor 2
SENSOR2_CS = 0; //CS low to select sensor 2 and start transmission
//On the falling edge of CS, 2-byte command written to control register
junk = spi(WRITE_REGISTER); //Initiate write to the control register
junk = spi(DEFAULT_MODE); //Set enable bit in the register
SENSOR2_CS = 1; //CS goes high at the end of transmission
//Sensor 3
SENSOR3_CS = 0; //CS low to select sensor 3 and start transmission
//On the falling edge of CS, 2-byte command written to control register
junk = spi(WRITE_REGISTER); //Initiate write to the control register
junk = spi(DEFAULT_MODE); //Set enable bit in the register
SENSOR3_CS = 1; //CS goes high at the end of transmission
//Sensor 4
SENSOR4_CS = 0; //CS low to select sensor 4 and start transmission
//On the falling edge of CS, 2-byte command written to control register
junk = spi(WRITE_REGISTER); //Initiate write to the control register
junk = spi(DEFAULT_MODE); //Set enable bit in the register
SENSOR4_CS = 1; //CS goes high at the end of transmission
}
/****************************************************************************/
unsigned char get_sensor(unsigned char sensor, unsigned char axis) {
//Accelerometer Read Back Operation
//Sample, convert and read back sensor data with 12-bit ADC
unsigned char byte1, byte2, junk;
switch(sensor) {
case 1: //Sensor 1
SENSOR1_CS = 0; //CS low to select chip and start transmission
//On the falling edge of CS, 2-byte command written to control reg
junk = spi(axis); //Send command to initiate conversion of axis
//There must be a minimum of 40us between the first and second
//bytes to give the A/D conversion enough time to complete
delay_us(50);
byte1 = spi(0x00); //Read in most significant 8 bits
byte2 = spi(0x00); //Read in least significant 4 bits
SENSOR1_CS = 1; //CS goes high at the end of transmission
//Return only 7 most significant bits
return (byte1>>1);
case 2: //Sensor 2
SENSOR2_CS = 0; //CS low to select chip and start transmission
//On the falling edge of CS, 2-byte command written to control reg
junk = spi(axis); //Send command to initiate conversion of axis
//There must be a minimum of 40us between the first and second
//bytes to give the A/D conversion enough time to complete
delay_us(50);
byte1 = spi(0x00); //Read in most significant 8 bits
byte2 = spi(0x00); //Read in least significant 4 bits
SENSOR2_CS = 1; //CS goes high at the end of transmission
//Return only 7 most significant bits
return (byte1>>1);
case 3: //Sensor 3
SENSOR3_CS = 0; //CS low to select chip and start transmission
//On the falling edge of CS, 2-byte command written to control reg
junk = spi(axis); //Send command to initiate conversion of axis
//There must be a minimum of 40us between the first and second
//bytes to give the A/D conversion enough time to complete
delay_us(50);
byte1 = spi(0x00); //Read in most significant 8 bits
byte2 = spi(0x00); //Read in least significant 4 bits
SENSOR3_CS = 1; //CS goes high at the end of transmission
//Return only 7 most significant bits
return (byte1>>1);
case 4: //Sensor 4
SENSOR4_CS = 0; //CS low to select chip and start transmission
//On the falling edge of CS, 2-byte command written to control reg
junk = spi(axis); //Send command to initiate conversion of axis
//There must be a minimum of 40us between the first and second
//bytes to give the A/D conversion enough time to complete
delay_us(50);
byte1 = spi(0x00); //Read in most significant 8 bits
byte2 = spi(0x00); //Read in least significant 4 bits
SENSOR4_CS = 1; //CS goes high at the end of transmission
//Return only 7 most significant bits
return (byte1>>1);
}
}
/****************************************************************************/