Add sample latency program for Lime2.

coupler/test_latency.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+/*
+ * Simple C program which tests system latency by writing every cycle 1 or 0
+ * to respective GPIO (configured to STMP157-OLinuXino-LIME2 with STMP15X-SHIELD)
+ */
+#include <stdint.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <linux/gpio.h>
+
+int main() {
+	int fd;
+	struct gpiohandle_request led;
+	struct gpiohandle_data data;
+
+	 /* Schema
+	 * GND: pin 2
+	 *    : pin 9
+	 * */
+
+	fd = open("/dev/gpiochip1", O_RDWR);
+	if(fd < 0) {
+		perror("Error opening gpiochip");
+		return -1;
+	}
+
+	/* Setup LED to output */
+	led.flags = GPIOHANDLE_REQUEST_OUTPUT;
+	strcpy(led.consumer_label, "LED");
+	memset(led.default_values, 0, sizeof(led.default_values));
+	led.lines = 1;
+	led.lineoffsets[0] = 7;
+
+	if(ioctl(fd, GPIO_GET_LINEHANDLE_IOCTL, &led) < 0) {
+		perror("Error setting GPIO to output");
+		close(fd);
+		return -1;
+	}
+
+	/* Let's set the LED */
+	int i;
+	int b = 1;
+	for (i=1; i<100000000; ++i) {
+	  data.values[0] = b;
+	  if (b) b = 0;
+	  else b = 1;
+	  if(ioctl(led.fd, GPIOHANDLE_SET_LINE_VALUES_IOCTL, &data) < 0) 
+		perror("Error setting GPIO to 1");
+          //printf("b=%d\n", b);
+	  //sleep(2);
+        }
+	// close fds
+	close(fd);
+	close(led.fd);
+	return 0;
+}