gbasend.c

// view from front of CABLE
// annotated with colors of crappy $1 ebay link cable
//   T
// 1 3 5         1 3v, xxx 3 SI, wht 5 SC, red
// 2 4 6         2 SO, blk 4 SD, grn 6 GN, xxx

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>

#include <wiringPi.h>

const int CHANNEL = 1;
const int SD = 3;
const int SI = 12;
const int SO = 13;
const int SC = 14;

uint8_t buffer[2] = {0};

uint8_t* pack_buffer(uint16_t write16) {
	buffer[0] = (write16 & 0xff00) >> 8;
	buffer[1] = write16 & 0x00ff;

	return buffer;
}

uint16_t unpack_buffer() {
	return (buffer[0] << 8) | buffer[1];
}

uint32_t writeSPI32bits(uint32_t write32) {
	printf("writing 0x%08x\n", write32);

	digitalWrite(SD, 0);
	pack_buffer(write32 && 0xffff);
	wiringPiSPIDataRW(CHANNEL, buffer, 2);
	uint16_t short0 = unpack_buffer();
	digitalWrite(SD, 1);

	digitalWrite(SD, 0);
	pack_buffer(write32 >> 16);
	wiringPiSPIDataRW(CHANNEL, buffer, 2);
	uint16_t short1 = unpack_buffer();
	digitalWrite(SD, 1);

	return (short1 << 16) | short0;
}

int main(int argc, char* argv[]) {

	wiringPiSPISetupMode(CHANNEL, 100000, 3);
	pinMode(SD, 1);
	digitalWrite(SD, 1);

	uint32_t read_from_gba = 0;

	while (read_from_gba != 0x72026202) {
		read_from_gba = writeSPI32bits(0x00006202);
		printf("got 0x%08x\n\n", read_from_gba);
		usleep(1000000);
	}

	printf("found gba\n");

	return 1;
}