I have completed the code for the SCP and the following should print out temperature in Fahrenheit and pressure in Pascals. The other register are defined if you wanted to return the revision ID or opstatus etc. I think the problem the author had was not timing but never sending a initial command to choose the SCP operation mode. This line is in the setup(). Feel free to ask a question or let me know if you see something inefficient or wrong.
// define spi bus pins
#define SLAVESELECT 10
#define SPICLOCK 13
#define DATAOUT 11 //MOSI
#define DATAIN 12 //MISO
#define UBLB(a,b) ( ( (a) << 8) | (b) )
#define UBLB19(a,b) ( ( (a) << 16 ) | (b) )
//Addresses
#define REVID 0x00 //ASIC Revision Number
#define OPSTATUS 0x04 //Operation Status
#define STATUS 0x07 //ASIC Status
#define START 0x0A //Constant Readings
#define PRESSURE 0x1F //Pressure 3 MSB
#define PRESSURE_LSB 0x20 //Pressure 16 LSB
#define TEMP 0x21 //16 bit temp
char rev_in_byte;
int temp_in;
unsigned long pressure_lsb;
unsigned long pressure_msb;
unsigned long temp_pressure;
unsigned long pressure;
void setup()
{
byte clr;
pinMode(DATAOUT, OUTPUT);
pinMode(DATAIN, INPUT);
pinMode(SPICLOCK,OUTPUT);
pinMode(SLAVESELECT,OUTPUT);
digitalWrite(SLAVESELECT,HIGH); //disable device
SPCR = B01010011; //MPIE=0, SPE=1 (on), DORD=0 (MSB first), MSTR=1 (master), CPOL=0 (clock idle when low), CPHA=0 (samples MOSI on rising edge), SPR1=0 & SPR0=0 (500kHz)
clr=SPSR;
clr=SPDR;
delay(10);
Serial.begin(9600);
delay(500);
Serial.println("Initialize High Speed Constant Reading Mode");
write_register(0x03,0x09);
}
void loop()
{
rev_in_byte = read_register(REVID);
pressure_msb = read_register(PRESSURE);
pressure_msb &= B00000111;
pressure_lsb = read_register16(PRESSURE_LSB);
pressure = UBLB19(pressure_msb, pressure_lsb);
pressure /= 4;
Serial.print("PRESSURE [");
Serial.print(pressure, DEC);
Serial.println("]");
temp_in = read_register16(TEMP);
temp_in = temp_in / 20;
temp_in = ((1.8) *temp_in) + 32;
Serial.print("TEMP F [");
Serial.print(temp_in , DEC);
Serial.println("]");
delay(1500);
}
char spi_transfer(volatile char data)
{
SPDR = data; // Start the transmission
while (!(SPSR & (1<<SPIF))) // Wait for the end of the transmission
{
};
return SPDR; // return the received byte
}
char read_register(char register_name)
{
char in_byte;
register_name <<= 2;
register_name &= B11111100; //Read command
digitalWrite(SLAVESELECT,LOW); //Select SPI Device
spi_transfer(register_name); //Write byte to device
in_byte = spi_transfer(0x00); //Send nothing, but we should get back the register value
digitalWrite(SLAVESELECT,HIGH);
delay(10);
return(in_byte);
}
float read_register16(char register_name)
{
byte in_byte1;
byte in_byte2;
float in_word;
register_name <<= 2;
register_name &= B11111100; //Read command
digitalWrite(SLAVESELECT,LOW); //Select SPI Device
spi_transfer(register_name); //Write byte to device
in_byte1 = spi_transfer(0x00);
in_byte2 = spi_transfer(0x00);
digitalWrite(SLAVESELECT,HIGH);
in_word = UBLB(in_byte1,in_byte2);
return(in_word);
}
void write_register(char register_name, char register_value)
{
register_name <<= 2;
register_name |= B00000010; //Write command
digitalWrite(SLAVESELECT,LOW); //Select SPI device
spi_transfer(register_name); //Send register location
spi_transfer(register_value); //Send value to record into register
digitalWrite(SLAVESELECT,HIGH);
}