Add a delay between sending the commands.

When trying to send the commands as fast as possible, without any delay,
the failure rate is very high. Almost every single packet fails with a
timeout at first. Retrying the packet works, but those many timeouts
make the download extremely slow. Adding a small delay avoids the much
more expensive timeout and speeds up the transfer significantly.

src/mares_common.c

@@ -49,6 +49,7 @@ mares_common_device_init (mares_common_device_t *device, const device_backend_t
 	// Set the default values.
 	device->port = NULL;
 	device->echo = 0;
+	device->delay = 0;
 }
 
 
@@ -128,6 +129,10 @@ mares_common_packet (mares_common_device_t *device, const unsigned char command[
 	if (device_is_cancelled (abstract))
 		return DEVICE_STATUS_CANCELLED;
 
+	if (device->delay) {
+		serial_sleep (device->delay);
+	}
+
 	// Send the command to the device.
 	int n = serial_write (device->port, command, csize);
 	if (n != csize) {

src/mares_common.h

@@ -43,6 +43,7 @@ typedef struct mares_common_device_t {
 	device_t base;
 	serial_t *port;
 	unsigned int echo;
+	unsigned int delay;
 } mares_common_device_t;
 
 void

src/mares_darwin.c

@@ -162,6 +162,7 @@ mares_darwin_device_open (device_t **out, const char* name, unsigned int model)
 
 	// Override the base class values.
 	device->base.echo = 1;
+	device->base.delay = 50;
 
 	*out = (device_t *) device;