USART IN SPI MODE COMMUNICATION BETWEEN TLC5971 and Atmega1284P

I have written the codes below for communication between TLC5971 and Atmega1284P microcontroller, but I still have some doubts. 

#include "TLC5971.h"
#include <util/delay.h>



void TLC5971_init(void)
{
	// Function control to set all Outputs off
	fc = TLC5971_BLANK;				// Sets Bit 213 to 1
	// Brightness control: Sets brightness control to full by default
	bc[0]= 127;
	bc[1]= 127;
	bc[2]= 127;

		
}

/************************************ SETTING THE DATA  *******************************************/
// set the LEDs Parameters
//- *fc: array of N euint8 for Function control - {fc0, fc1, ... , fcN }
//- *bc: array of N*3 euint8 for Brightness correction-{bcR0, bcG0, bcB0, bcR1, bcG1,... , bcBN }
//- *gs: array of N*12 euint16 for Grayscale data (PWM)-{gs0.0, gs0.1, gs0.2, gs0.3, gs0.4, ... , gs1.0, gs1.1, ... , gsN.12 }

// Set FC
void setFC(uint8_t f)
{
	fc = f;
}

// Set Grayscale
void setGS(uint16_t *g)
{
	uint8_t N = 22;				// The number of TLC5971 pieces

	
	// do this for all the drivers
	for (int8_t i=N-1; i>=0; i--)
	{
		// Grayscale data - 12x 16-bit words per driver
		gs = g + (12*i);
		// Send the write command
		sendWriteCommand();
		// Function control data
		sendFC();
		// Brightness correction
		sendBC();
		// Grayscale data
		sendGS();
	}

}

/* 
	This is used if the TLC5971 is driving LEDs with same colours 
	It sets the level of brightness of the LEDs from 0 to 127 (128 Levels)
*/
void setBC(uint8_t b)
{
	int8_t i;
	// BC has 128 Steps - i = 0,1,2
	for (i=0; i<3; i++)
	{
		if (b<127)
		{
			bc[i]= b;
		}
		else {
			bc[i]=127;
		}
	}
}

/* 
	This is used if the TLC5971 is driving LEDs with different colours
	It sets the level of brightness of the three different colours
	from 0 to 127 (128 Levels)
*/
/*
void setBC(uint8_t *b)
{
	for (uint8_t i=0; i<3; i++)
	{
		if (b[i] < 128)
		{
			bc[i] = b[i];
		}
		else
		{
			bc[i] = 127;
		}
	}
}
*/

/**************** SENDING THE DATA : Send MSB First *****************/

// sends the LEDs data
//- *Command: 6-bits (0x25 = 0b1001010 is sent, to enable copying of the 218 bit data in the 224-bit register to the 218-bit data latch
//- *fc: 5-bits of Function control of TLC5971 - {OUTMG, EXTGCK, TMGRST , DSPRPT, BLANK }
//- *bc: 21-bits with 7-bits of each of the colours of TLC5971 for OUTRn, OUTGn, OUTBn - {}
//- *gs: 192-bits with 16-bits for each of the 12 channels of TLC5971-{OUTB3,..., OUTB0, OUTG3,...,OUTG0, OUTR3,..., OUTR0}

// Send the write command to the device (6-bits = 0x25 = 0b100101
void sendWriteCommand()
{
	shiftData(0x25,6);
	
}

// Send the Function Control (FC)
void sendFC()
{
	shiftData(fc,5);
}

// Send the Brightness Control (BC)
void sendBC()
{
	uint8_t j = 0;
	// For 7-bits for each of the three colours:j=0,1,2
	for (j=2; j>=2; j--)
	{
		shiftData(bc[j],7);
	}
}

// Send the Grayscale
void sendGS()
{
	
	uint8_t j = 0;
	// For the 12 channels: j = 0, 1, 2 ....
	for (j=11; j>=0; j--)
	{
		// Shifting the bits of a 16-bit integer by 8 places to the right 
		// gives the Most Significant Byte of the 16-bit integer
		uint8_t Hi = (uint8_t)(gs[j]>>8);
		
		// Masking bits to 1 of the 16-bit integer with an 8-bit integer 
		// grabs the Least Significant Byte of the 16-bit integer
		uint8_t Lo = (uint8_t)(gs[j]&0xFF);
		
		// Shifting the Most Significant Byte
		shiftData(Hi,8);
		// Shifting the Least Significant Byte
		shiftData(Lo,8);
	}
	
}

// Sends LED parameters : num is number of bits in data
void shiftData(uint8_t data, uint8_t num)
{
	uint8_t i = 0;
	uint8_t tlcData;
	usartSPI_init();
	
	for (i=num-1; i>=0; i--)
	{
		usartSPI_write(tlcData);
	}
	
	_delay_us(0.64); //640ns wait time  for SCKI speed of 12.5MHz
}

I would appreciate if I can get some feedbacks

Kind regards

SOSO