Master SPI Port

Initialise

#define INTERBOARD_COMMS_SS_PIN				LATDbits.LATD3
#define INTERBOARD_COMMS_PACKET_LENGTH		10

	//----- SETUP SSP2 AS SPI BUS -----
	//Used for: 
	//CLK idle in low state
	//Devices clock in data on the rising edge, output data on the falling edge
	SSP2STAT = 0b11000000;
	SSP2CON1 = 0b00100010;		//16MHz Fosc / 64 = 250000kHz

	//----- INIT SPI -----
	//Send a dummy byte to trigger the BF bit
	SSP2BUF = 0;
	INTERBOARD_COMMS_SS_PIN = 1;

TX and Receive

		//Exit if TX in progress
		if (!SSP2STATbits.BF)
			return;

		//Exit if pausing
		if (interboard_comms_10ms_timer > 0)
			return;

		if (spi_comms_byte_index == 0xff)
		{
			//DONE COMPLETE PACKET
			Nop();		//Ensure a delay after clock of last byte
			Nop();
			Nop();
			Nop();
			Nop();
			INTERBOARD_COMMS_SS_PIN = 1;

			spi_comms_byte_index = 0;
			interboard_comms_10ms_timer = 2;		//Wait 10-20ms before next comms
			return;
		}


		if (spi_comms_byte_index == 0)
		{
			//----- BYTE 0 -----
			INTERBOARD_COMMS_SS_PIN = 0;

			spi_tx_rx_data[0] = 0x10;
			spi_tx_rx_data[1] = 0x11;
			spi_tx_rx_data[2] = 0x12;
			spi_tx_rx_data[3] = 0x13;
			spi_tx_rx_data[4] = 0x14;
			spi_tx_rx_data[5] = 0x15;
			spi_tx_rx_data[6] = 0x16;
			spi_tx_rx_data[7] = 0x17;
			spi_tx_rx_data[8] = 0x18;
			spi_tx_rx_data[9] = 0x19;
		}

		data = SSP2BUF;
		SSP2BUF = spi_tx_rx_data[spi_comms_byte_index];
		spi_tx_rx_data[spi_comms_byte_index] = data;


		spi_comms_byte_index++;
		if (spi_comms_byte_index >= INTERBOARD_COMMS_PACKET_LENGTH)
			spi_comms_byte_index = 0xff;		//Flag packet all done

Slave SPI Port

Initialise

	//----- SETUP SSP2 AS SPI BUS -----
	//SLAVE MODE
	TRISDbits.TRISD0 = 1;
	TRISDbits.TRISD3 = 1;
	SSP2STAT = 0b01000000;
	SSP2CON1 = 0b00100100;		//SPI slave mode, SS is used

	PIE3bits.SSP2IE = 1;		//Enable interrupt