mmc.c.txt

PIC MMC 基于spi 模式读写样例

/*	PIC MMC Interface Test
	http://www.captain.at/electronics/
	
	Writes ASCII characters to the MMC, reads them back and sends the characters
	to the linux machine via the serial port. Use "serterm" for testing:

	# ./serterm
	baud=9600
	baud=9600
	listening...
	PIC online MMC online 0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcde
	fghijklmno0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmno01
	23456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmno0123456789:;<=
	>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnoCCCCCCCCCCCCCCCCCCCCCCCCCC
	CCCCCCCCCCC [more C's follow]
	exiting...
	
	Furthermore the PIC returns any character sent to it via the interrupt
	service routine. Use "ser" for testing:
	
	# ./ser
	baud=9600
	baud=9600
	written:ABC
	readport=ABC
	#
	
	Compile with CC5x: http://www.bknd.com/cc5x/
	c:\picc\cc5x mmc.c -Ic:\picc\ -ammc.ASM -u
	
	CC5x runs nicely on Linux with "dosemu" http://www.dosemu.org/
	
	Credit:
	SPI functions made by Michael Dworkin
	http://home.wtal.de/Mischka/MMC/
*/

#include <16F876.h>
#include "int16CXX.H"	// interrupt stuff

#define CP_off  |= 0x3F30
#define LVP |= 128
#pragma config CP_off,PWRTE=on,WDTE=off,FOSC=HS,BODEN=on,LVP

#pragma bit CS @ PORTC.2	// output pin for chip select (MMC)

#pragma rambank 0
char sector1[64];
int currentrambank;
int counter;

#pragma rambank 1
char sector2[64];

#pragma rambank 2
char sector3[64];

#pragma rambank 3
char sector4[64];

#pragma origin 4		// force interrupt service routine at address 4

interrupt myInterrupt(void)		// ISR
{
	int_save_registers
	char rec;
	if (RCIF)				// USART interrupt ?
	{
		while(!TXIF) {		// wait for serial register to be sent, if there is still something in there
			nop();
		}
		rec = RCREG;		// Get the received character
		TXREG = rec;		// write to serial register -> start transmission

		RCIF = 0;			// clear USART int flag
	}
	int_restore_registers
}

void InitUSART()
{
	PORTA = 0;
	PORTB = 0;
	PORTC = 0;
	
	BRGH = 1;		// high speed serial mode
	SPBRG = 25;		// Set 9600 baud for 4 MHz oscillator
	SYNC = 0;		// Clear SYNC bit -> Set ASYNC Mode
	SPEN = 1;		// Set serial port enable
	TX9 = 0;			// 8-bit transmissions
	TXEN = 1;		// Enable transmission
	RCIE = 1;		// Rx interrupts are desired
	RX9 = 0;			// 8-bit receptions
	CREN = 1;		// Enable reception
}

void initint()		// init interrupts
{
	GIE = 1; 		// Set Global Interrupt Enable
	PEIE = 1;		// Set Peripheral Interrupt Enable
}

void fillram()		// fill RAM (sector1..4) with ASCII characters
{
	int i;
	int x;
	for (i=0;i<=63;i++) {
		x = i + 48;
		sector1[i] = x;
		sector2[i] = x;
		sector3[i] = x;
		sector4[i] = x;
	}
}

char SPI(char d)		// send character over SPI
{
	SSPBUF = d;			// send character
	while (!BF);		// wait until sent
	return SSPBUF;		// and return the received character
}

char Command(char befF,uns16 AdrH,uns16 AdrL,char befH )
{	// sends a command to the MMC
	char a;
	SPI(0xFF);
	SPI(befF);
	SPI(AdrH.high8);
	SPI(AdrH.low8);
	SPI(AdrL.high8);
	SPI(AdrL.low8);
	SPI(befH);
	SPI(0xFF);
	return SPI(0xFF);	// return the last received character
}

bit MMC_Init()	// init SPI
{
	SMP = 0;		// input is valid in the middle of clock
	CKE = 0;		// rising edge is data capture
	CKP = 1;		// high value is passive state
	SSPM1 = 1;	// speed f/64(312kHz), Master
	SSPEN = 1;	// enable SPI
	CS = 1; 		// disable MMC

	char i;
	// start MMC in SPI mode
	for(i=0; i < 10; i++)SPI(0xFF);		// send 10*8=80 clock pulses
	CS=0;			// MMC-Enabled

	if (Command(0x40,0,0,0x95) !=1) goto mmcerror; 	// Reset MMC

st: // if there is no MMC, prg. loops here
	if (Command(0x41,0,0,0xFF) !=0) goto st;

	return 1;
mmcerror:
	return 0;
}

void serialterminate() { // terminate sent string!!!
	while(!TXIF);
	TXREG = 0x0d;
	while(!TXIF);
	TXREG = 0x0a;
}

void SerString(const char *str)	// send string via RS232
{
	char ps;
	ps = *str;					// pointer of start of string into ps
	while(ps>0)					// test if end of string is reached
	{
		str++;					// set pointer to next char
		if (ps== 0) break;	// test if end of string is reached
		while(!TXIF);			// test if TXREG empty
		TXREG = ps ;			// send character
	  	ps = *str;				// content of pointer into ps
	}
	serialterminate();
}

bit writeramtommc()		// write RAM (sector1..4) to MMC
{
	// 512 byte-write-mode
	if (Command(0x58,0,512,0xFF) !=0) {
		SerString("MMC: write error 1 ");
		return 1;	
	}
	SPI(0xFF);
	SPI(0xFF);
	SPI(0xFE);
	uns16 i;
	// write ram sectors to MMC
	for (i=0;i<=63;i++) {
		SPI(sector1[i]);
	}
	for (i=0;i<=63;i++) {
		SPI(sector2[i]);
	}
	for (i=0;i<=63;i++) {
		SPI(sector3[i]);
	}
	for (i=0;i<=63;i++) {
		SPI(sector4[i]);
	}
	for (i=0;i<256;i++) { 	// fill rest with 'C'
		SPI('C');
	}
	SPI(255);					// at the end, send 2 dummy bytes
	SPI(255);

	i = SPI(0xFF);
	i &= 0b.0001.1111;
	if (i != 0b.0000.0101) {
		SerString("MMC: write error 2 ");
		return 1;
	}
	while(SPI(0xFF) != 0xFF);	// wait until MMC is not busy anymore
	return 0;
}

bit sendmmc()		// send 512 bytes from the MMC via the serial port
{
	uns16 i;
	// 512 byte-read-mode 
	if (Command(0x51,0,512,0xFF) !=0) {
		SerString("MMC: read error 1 ");
		return 1;
	}
	while(SPI(0xFF) != 0xFE);	// wait for 0xFE - start of any transmission
	for(i=0; i < 512; i++)
	{
		while(!TXIF);   			// wait until TXREG is empty
		TXREG = SPI(0xFF);		// get MMC byte and send via RS232
	}
	serialterminate();
	SPI(0xFF);						// at the end, send 2 dummy bytes
	SPI(0xFF);
	return 0;
}

void main(void)
{
	InitUSART();					// initialize serial port
	initint();						// initialize interrupts

	ADCON1=0x6;						// PortA Digital
	// set ports for I/O
	TRISC = 0b.1101.0011;		// sck rc3-0, sdo rc5-0, CS rc2-0.
	TRISB = 0b.0000.0010;   	// RB2>TX, RB1>RX

	SerString("PIC online ");	// start message
//	SerString(0x00);	// start message
	
	// init MMC and send message if ok
	if (MMC_Init()) SerString("MMC online ");
	
	fillram(); 						// fill the RAM with ASCII characters
	writeramtommc();				// write RAM to MMC
	sendmmc();						// send 512 bytes of the MMC via serial port
			
	while(1) {
		nop();
		nop();
	}
}