Digital to Analog Conversion using Cordic - c

Question

I am a newbie with DACs, but basically, I have a FPGA (DE1-SOC) running Linux. Hooked up to it is a LTC2607 DAC. Everything is operating smoothly as far as Linux recognizing the DAC over I2C and everything.
My question is regarding how to generate a sinusoidal waveform using the cordic algorithm. I have an algorithm that outputs an array of 16 hex values.
{0x00003243, 0x00001DAC, 0x00000FAD, 0x000007F5, etc...}
The code that runs the I2c/DAC accepts a 16-bit "DAC Code", which then is converted to an analog output:
uint16_t LTC2607_code(float dac_voltage, float LTC2607_lsb, float LTC2607_offset)
{
uint16_t dac_code;
float float_code;
float_code = (dac_voltage - LTC2607_offset) / LTC2607_lsb; // Calculate the DAC code
float_code = (float_code > (floor(float_code) + 0.5)) ? ceil(float_code) : floor(float_code); // Round
if (float_code >= 65535.0) // Limits the DAC code to 16 bits
float_code = 65535.0;
dac_code = (uint16_t) (float_code); // Convert to unsigned integer
return (dac_code);
}
I know for direct digital synthesis you have to "interpolate" the points (voltage levels) along the sinusoid. My thinking is that I would send those value across the I2C, one-by-one, and however fast those 16 hex values are passed across the I2C (set by the Master (FPGA) clock # ~10MHz) is what frequency the sin wave will be?
The code for writing to the DAC is as follows:
int8_t LTC2607_write(uint8_t i2c_address, uint8_t dac_command, uint8_t dac_address, uint16_t dac_code)
{
int fd;
int ret;
char *device;
uint8_t command_byte;
uint8_t buffer[3];
command_byte = dac_command | dac_address; // Build the DAC command byte
// Open the I2C device
device = LTC2607_get_device_name();
fd = open(device, O_RDWR);
if (fd < 0)
{
return (1);
}
// Select the desired address
ret = ioctl(fd, I2C_SLAVE, i2c_address);
if (ret < 0)
{
close(fd);
return (1);
}
// Build the I2C command
buffer[0] = command_byte;
buffer[1] = (dac_code >> 8) & 0xFF;
buffer[2] = dac_code & 0xFF;
// Write the command to the I2C bus
ret = write(fd, buffer, 3);
if (ret < 3)
{
close(fd);
return (1);
}
// Close the device
close(fd);
return (0);
}
How would I convert that string of 16 hex values into a sinusoid using the above LTC2607_write function?