ADS8681: Regarding Configuration

Hello Everyone, 

I am a New user of ADS8681 ADC and Also New to this Type of ADC After Reading The Datasheet I Have some Questions Please Help me

1) I am Trying to Read the Adc value So this is +- Adc so How do the Resolution Values vary (I Read the Datasheet but I didn't Understand).

2) What is the Programming Flow for the Configure Adc For +-1.25*Vref (we are using Internal ref.) (Which Register are Required to Configure) which Command is used for set the Register like Hword or Write. and How I Create Register Values. 

3) I am Using Beagle bone Black For Interfacing Adc So I using C code, Right Now I Am Not Configuring anything So when I read through Spi it Gives me Approx 41795 Resolutions for 3.3v Input and Approx 32764 for 0v/ GND is it Correct?

4) What the Formula for Calcuate the Voltage with Resolution for +- Adc (I know the Normal one i.e.  vout= (vref/ 2^no of bits Adc) * Resolution Value) but I think it is not working with this.

I am Using the Following Code

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>

#define SPI_DEVICE "/dev/spidev1.0"
#define SPI_MODE SPI_MODE_0
#define SPI_SPEED 100000 // 100 kHz

int spi_fd;

// Function to initialize SPI communication
int spi_init() {
spi_fd = open(SPI_DEVICE, O_RDWR);
if (spi_fd == -1) {
perror("Error opening SPI device");
return -1;
}

uint8_t mode = SPI_MODE;
if (ioctl(spi_fd, SPI_IOC_WR_MODE, &mode) == -1) {
perror("Error setting SPI mode");
close(spi_fd);
return -1;
}

uint32_t speed = SPI_SPEED;
if (ioctl(spi_fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed) == -1) {
perror("Error setting SPI speed");
close(spi_fd);
return -1;
}

return 0;
}

// Function to transmit data over SPI
void spi_transmit(uint16_t *data, size_t len) {
struct spi_ioc_transfer transfer = {
.tx_buf = (unsigned long)data,
.len = len,
};

if (ioctl(spi_fd, SPI_IOC_MESSAGE(1), &transfer) == -1) {
perror("Error transmitting SPI data");
}
}

// Function to receive data over SPI
void spi_receive(uint16_t *data, size_t len) {
struct spi_ioc_transfer transfer = {
.rx_buf = (unsigned long)data,
.len = len,
};

if (ioctl(spi_fd, SPI_IOC_MESSAGE(1), &transfer) == -1) {
perror("Error receiving SPI data");
}
}

// Function to close SPI communication
void spi_close() {
close(spi_fd);
}

int main() {
if (spi_init() == -1) {
return 1;
}

// Example data
uint16_t tx_data[] = {0x0000};
size_t len = sizeof(tx_data);

// Transmit data
spi_transmit(tx_data, len);

while(1)
{

// Receive data
uint16_t rx_data[len];
spi_receive(rx_data, len);

printf("Received data In Decimal: ");
for (size_t i = 0; i < len; ++i) {
printf("%d ", rx_data[i]);
}
printf("\n");

printf("Received data In hex: ");
for (size_t i = 0; i < len; ++i) {
printf("0x%X", rx_data[i]);
}
printf("\n");
usleep(1000000);


}
// Close SPI communication
spi_close();

return 0;
}

6) if Any one Has the C code for the ADS8681 or its Library/Driver Please Provide me.