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#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <termios.h>
#define BUFFER_START 0x2000u
//#define BUFFER_SIZE 960u
#define BUFFER_SIZE 10
#define BUFFER_END (BUFFER_START + BUFFER_SIZE)
#define RAM_SIZE (BUFFER_END + 1)
#define BOOL int
#define FALSE 0
#define TRUE 1
BOOL overrun = FALSE;
BOOL overrunForReader = FALSE;
BOOL underrun = TRUE;
char picRam[RAM_SIZE] = { 0 };
char* bufferStart = &(picRam[BUFFER_START]);
char* bufferEnd = &(picRam[BUFFER_END - 1]);
char* writePtr = 0;
char* readPtr = 0;
BOOL currentByteLoaded = FALSE;
char spiData = 0;
void debugPrint() {
printf("wPtr: %d, rPtr: %d, cbl: %d, ovr: %d, udr: %d\n",
(int) (writePtr - bufferStart),
(int) (readPtr - bufferStart),
(int) currentByteLoaded,
(int) overrun,
(int) underrun);
int i;
for(i = 0; i < BUFFER_SIZE; ++i) {
printf("%02x ", bufferStart[i]);
}
printf("\n");
}
int getch(void)
{
int ch;
struct termios oldt;
struct termios newt;
tcgetattr(STDIN_FILENO, &oldt); /*store old settings */
newt = oldt; /* copy old settings to new settings */
newt.c_lflag &= ~(ICANON | ECHO); /* make one change to old settings in new settings */
tcsetattr(STDIN_FILENO, TCSANOW, &newt); /*apply the new settings immediatly */
ch = getchar(); /* standard getchar call */
tcsetattr(STDIN_FILENO, TCSANOW, &oldt); /*reapply the old settings */
return ch; /*return received char */
}
void incrementWriteIdx() {
if (!underrun && (writePtr == readPtr)) {
overrun = TRUE;
overrunForReader = TRUE;
} else {
if (!overrun) {
writePtr++;
writePtr = writePtr > bufferEnd ? bufferStart : writePtr;
}
overrun = FALSE;
overrunForReader = FALSE;
underrun = FALSE;
}
}
void incrementReadIdx() {
if (!overrunForReader && (readPtr == writePtr)) {
underrun = TRUE;
} else {
readPtr++;
readPtr = readPtr > bufferEnd ? bufferStart : readPtr;
underrun = FALSE;
overrunForReader = FALSE;
// overrun = FALSE;
}
}
void beginRead() {
if (!currentByteLoaded) {
incrementReadIdx();
}
if (!underrun) {
spiData = *readPtr;
printf("SPI out: %02x\n", (int)spiData);
}
currentByteLoaded = TRUE;
}
void endRead() {
currentByteLoaded = FALSE;
}
void storeSample() {
static char value = 0;
value++;
incrementWriteIdx();
if (!overrun) {
*writePtr = value;
}
}
void triggerByteTransferred() {
if (spiData == 0) {
endRead();
beginRead();
} else if (spiData == 'r') {
beginRead();
} else {
printf("%s", "I don't like you!");
}
}
int main()
{
writePtr = bufferStart;
readPtr = bufferStart;
char key;
for(;;) {
/*ssize_t len = read(0, &key, 1);
if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
continue;
} else if (len == 0) {
return 0;
} else if (len != 1) { abort(); }*/
debugPrint();
key = getch();
switch(key) {
case '+': storeSample(); break;
case '0': spiData = 0; triggerByteTransferred(); break;
case 'q': return 0;
default: spiData = key; triggerByteTransferred(); break;
}
}
return 0;
}
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