diff --git a/src/oceanic_atom2.c b/src/oceanic_atom2.c
index f950744..892b073 100644
--- a/src/oceanic_atom2.c
+++ b/src/oceanic_atom2.c
@@ -85,18 +85,6 @@ device_is_oceanic_atom2 (device_t *abstract)
 }
 
 
-static device_status_t
-oceanic_atom2_send (oceanic_atom2_device_t *device, const unsigned char command[], unsigned int csize)
-{
-	// Send the command to the dive computer and 
-	// wait until all data has been transmitted.
-	serial_write (device->port, command, csize);
-	serial_drain (device->port);
-
-	return DEVICE_STATUS_SUCCESS;
-}
-
-
 static device_status_t
 oceanic_atom2_transfer (oceanic_atom2_device_t *device, const unsigned char command[], unsigned int csize, unsigned char answer[], unsigned int asize)
 {
@@ -110,14 +98,14 @@ oceanic_atom2_transfer (oceanic_atom2_device_t *device, const unsigned char comm
 	unsigned char response = NAK;
 	while (response == NAK) {
 		// Send the command to the dive computer.
-		device_status_t rc = oceanic_atom2_send (device, command, csize);
-		if (rc != DEVICE_STATUS_SUCCESS) {
+		int n = serial_write (device->port, command, csize);
+		if (n != csize) {
 			WARNING ("Failed to send the command.");
-			return rc;
+			return EXITCODE (n);
 		}
 
 		// Receive the response (ACK/NAK) of the dive computer.
-		int n = serial_read (device->port, &response, 1);
+		n = serial_read (device->port, &response, 1);
 		if (n != 1) {
 			WARNING ("Failed to receive the answer.");
 			return EXITCODE (n);
@@ -165,15 +153,15 @@ oceanic_atom2_init (oceanic_atom2_device_t *device)
 {
 	// Send the command to the dive computer.
 	unsigned char command[3] = {0xA8, 0x99, 0x00};
-	device_status_t rc = oceanic_atom2_send (device, command, sizeof (command));
-	if (rc != DEVICE_STATUS_SUCCESS) {
+	int n = serial_write (device->port, command, sizeof (command));
+	if (n != sizeof (command)) {
 		WARNING ("Failed to send the command.");
-		return rc;
+		return EXITCODE (n);
 	}
 
 	// Receive the answer of the dive computer.
 	unsigned char answer[3] = {0};
-	int n = serial_read (device->port, answer, sizeof (answer));
+	n = serial_read (device->port, answer, sizeof (answer));
 	if (n != sizeof (answer)) {
 		WARNING ("Failed to receive the answer.");
 		return EXITCODE (n);
@@ -194,15 +182,15 @@ oceanic_atom2_quit (oceanic_atom2_device_t *device)
 {
 	// Send the command to the dive computer.
 	unsigned char command[4] = {0x6A, 0x05, 0xA5, 0x00};
-	device_status_t rc = oceanic_atom2_send (device, command, sizeof (command));
-	if (rc != DEVICE_STATUS_SUCCESS) {
+	int n = serial_write (device->port, command, sizeof (command));
+	if (n != sizeof (command)) {
 		WARNING ("Failed to send the command.");
-		return rc;
+		return EXITCODE (n);
 	}
 
 	// Receive the answer of the dive computer.
 	unsigned char answer[1] = {0};
-	int n = serial_read (device->port, answer, sizeof (answer));
+	n = serial_read (device->port, answer, sizeof (answer));
 	if (n != sizeof (answer)) {
 		WARNING ("Failed to receive the answer.");
 		return EXITCODE (n);
diff --git a/src/oceanic_veo250.c b/src/oceanic_veo250.c
index a4428d8..bbc83d6 100644
--- a/src/oceanic_veo250.c
+++ b/src/oceanic_veo250.c
@@ -86,21 +86,6 @@ device_is_oceanic_veo250 (device_t *abstract)
 }
 
 
-static device_status_t
-oceanic_veo250_send (oceanic_veo250_device_t *device, const unsigned char command[], unsigned int csize)
-{
-	// Discard garbage bytes.
-	serial_flush (device->port, SERIAL_QUEUE_INPUT);
-
-	// Send the command to the dive computer and 
-	// wait until all data has been transmitted.
-	serial_write (device->port, command, csize);
-	serial_drain (device->port);
-
-	return DEVICE_STATUS_SUCCESS;
-}
-
-
 static device_status_t
 oceanic_veo250_transfer (oceanic_veo250_device_t *device, const unsigned char command[], unsigned int csize, unsigned char answer[], unsigned int asize)
 {
@@ -113,15 +98,18 @@ oceanic_veo250_transfer (oceanic_veo250_device_t *device, const unsigned char co
 	unsigned int nretries = 0;
 	unsigned char response = NAK;
 	while (response == NAK) {
+		// Discard garbage bytes.
+		serial_flush (device->port, SERIAL_QUEUE_INPUT);
+
 		// Send the command to the dive computer.
-		device_status_t rc = oceanic_veo250_send (device, command, csize);
-		if (rc != DEVICE_STATUS_SUCCESS) {
+		int n = serial_write (device->port, command, csize);
+		if (n != csize) {
 			WARNING ("Failed to send the command.");
-			return rc;
+			return EXITCODE (n);
 		}
 
 		// Receive the response (ACK/NAK) of the dive computer.
-		int n = serial_read (device->port, &response, 1);
+		n = serial_read (device->port, &response, 1);
 		if (n != 1) {
 			WARNING ("Failed to receive the answer.");
 			return EXITCODE (n);
@@ -165,15 +153,15 @@ oceanic_veo250_init (oceanic_veo250_device_t *device)
 {
 	// Send the command to the dive computer.
 	unsigned char command[2] = {0x55, 0x00};
-	device_status_t rc = oceanic_veo250_send (device, command, sizeof (command));
-	if (rc != DEVICE_STATUS_SUCCESS) {
+	int n = serial_write (device->port, command, sizeof (command));
+	if (n != sizeof (command)) {
 		WARNING ("Failed to send the command.");
-		return rc;
+		return EXITCODE (n);
 	}
 
 	// Receive the answer of the dive computer.
 	unsigned char answer[14] = {0};
-	int n = serial_read (device->port, answer, sizeof (answer));
+	n = serial_read (device->port, answer, sizeof (answer));
 	if (n != sizeof (answer)) {
 		WARNING ("Failed to receive the answer.");
 		return EXITCODE (n);
@@ -197,10 +185,10 @@ oceanic_veo250_quit (oceanic_veo250_device_t *device)
 {
 	// Send the command to the dive computer.
 	unsigned char command[2] = {0x98, 0x00};
-	device_status_t rc = oceanic_veo250_send (device, command, sizeof (command));
-	if (rc != DEVICE_STATUS_SUCCESS) {
+	int n = serial_write (device->port, command, sizeof (command));
+	if (n != sizeof (command)) {
 		WARNING ("Failed to send the command.");
-		return rc;
+		return EXITCODE (n);
 	}
 
 	return DEVICE_STATUS_SUCCESS;
diff --git a/src/oceanic_vtpro.c b/src/oceanic_vtpro.c
index eaa8b88..019182c 100644
--- a/src/oceanic_vtpro.c
+++ b/src/oceanic_vtpro.c
@@ -86,18 +86,6 @@ device_is_oceanic_vtpro (device_t *abstract)
 }
 
 
-static device_status_t
-oceanic_vtpro_send (oceanic_vtpro_device_t *device, const unsigned char command[], unsigned int csize)
-{
-	// Send the command to the dive computer and 
-	// wait until all data has been transmitted.
-	serial_write (device->port, command, csize);
-	serial_drain (device->port);
-
-	return DEVICE_STATUS_SUCCESS;
-}
-
-
 static device_status_t
 oceanic_vtpro_transfer (oceanic_vtpro_device_t *device, const unsigned char command[], unsigned int csize, unsigned char answer[], unsigned int asize)
 {
@@ -111,14 +99,14 @@ oceanic_vtpro_transfer (oceanic_vtpro_device_t *device, const unsigned char comm
 	unsigned char response = NAK;
 	while (response == NAK) {
 		// Send the command to the dive computer.
-		device_status_t rc = oceanic_vtpro_send (device, command, csize);
-		if (rc != DEVICE_STATUS_SUCCESS) {
+		int n = serial_write (device->port, command, csize);
+		if (n != csize) {
 			WARNING ("Failed to send the command.");
-			return rc;
+			return EXITCODE (n);
 		}
 
 		// Receive the response (ACK/NAK) of the dive computer.
-		int n = serial_read (device->port, &response, 1);
+		n = serial_read (device->port, &response, 1);
 		if (n != 1) {
 			WARNING ("Failed to receive the answer.");
 			return EXITCODE (n);
@@ -156,15 +144,15 @@ oceanic_vtpro_init (oceanic_vtpro_device_t *device)
 {
 	// Send the command to the dive computer.
 	unsigned char command[2] = {0xAA, 0x00};
-	device_status_t rc = oceanic_vtpro_send (device, command, sizeof (command));
-	if (rc != DEVICE_STATUS_SUCCESS) {
+	int n = serial_write (device->port, command, sizeof (command));
+	if (n != sizeof (command)) {
 		WARNING ("Failed to send the command.");
-		return rc;
+		return EXITCODE (n);
 	}
 
 	// Receive the answer of the dive computer.
 	unsigned char answer[13] = {0};
-	int n = serial_read (device->port, answer, sizeof (answer));
+	n = serial_read (device->port, answer, sizeof (answer));
 	if (n != sizeof (answer)) {
 		WARNING ("Failed to receive the answer.");
 		return EXITCODE (n);
diff --git a/src/uwatec_memomouse.c b/src/uwatec_memomouse.c
index 14cda3f..5b6c197 100644
--- a/src/uwatec_memomouse.c
+++ b/src/uwatec_memomouse.c
@@ -195,22 +195,6 @@ uwatec_memomouse_device_set_fingerprint (device_t *abstract, const unsigned char
 }
 
 
-static device_status_t
-uwatec_memomouse_confirm (uwatec_memomouse_device_t *device, unsigned char value)
-{
-	// Send the value to the device.
-	int rc = serial_write (device->port, &value, 1);
-	if (rc != 1) {
-		WARNING ("Failed to send the value.");
-		return EXITCODE (rc);
-	}
-
-	serial_drain (device->port);
-
-	return DEVICE_STATUS_SUCCESS;
-}
-
-
 static device_status_t
 uwatec_memomouse_read_packet (uwatec_memomouse_device_t *device, unsigned char data[], unsigned int size, unsigned int *result)
 {
@@ -271,9 +255,12 @@ uwatec_memomouse_read_packet_outer (uwatec_memomouse_device_t *device, unsigned
 		serial_flush (device->port, SERIAL_QUEUE_INPUT);
 
 		// Reject the packet.
-		rc = uwatec_memomouse_confirm (device, NAK);
-		if (rc != DEVICE_STATUS_SUCCESS)
-			return rc;
+		unsigned char value = NAK;
+		int n = serial_write (device->port, &value, 1);
+		if (n != 1) {
+			WARNING ("Failed to reject the packet.");
+			return EXITCODE (n);
+		}
 	}
 
 	return DEVICE_STATUS_SUCCESS;
@@ -304,9 +291,12 @@ uwatec_memomouse_read_packet_inner (uwatec_memomouse_device_t *device, dc_buffer
 			return rc;
 
 		// Accept the packet.
-		rc = uwatec_memomouse_confirm (device, ACK);
-		if (rc != DEVICE_STATUS_SUCCESS)
-			return rc;
+		unsigned char value = ACK;
+		int n = serial_write (device->port, &value, 1);
+		if (n != 1) {
+			WARNING ("Failed to accept the packet.");
+			return EXITCODE (n);
+		}
 
 		if (nbytes == 0) {
 			// The first packet should contain at least
@@ -370,9 +360,12 @@ uwatec_memomouse_dump_internal (uwatec_memomouse_device_t *device, dc_buffer_t *
 		serial_flush (device->port, SERIAL_QUEUE_INPUT);
 
 		// Reject the packet.
-		device_status_t rc = uwatec_memomouse_confirm (device, NAK);
-		if (rc != DEVICE_STATUS_SUCCESS)
-			return rc;
+		unsigned char value = NAK;
+		int n = serial_write (device->port, &value, 1);
+		if (n != 1) {
+			WARNING ("Failed to reject the packet.");
+			return EXITCODE (n);
+		}
 
 		serial_sleep (300);
 	}
@@ -413,8 +406,6 @@ uwatec_memomouse_dump_internal (uwatec_memomouse_device_t *device, dc_buffer_t *
 			return EXITCODE (n);
 		}
 
-		serial_drain (device->port);
-
 		// Wait for the answer (ACK).
 		n = serial_read (device->port, &answer, 1);
 		if (n != 1) {