diff --git a/include/libdivecomputer/hw_ostc3.h b/include/libdivecomputer/hw_ostc3.h
index 454d45c..8463cb2 100644
--- a/include/libdivecomputer/hw_ostc3.h
+++ b/include/libdivecomputer/hw_ostc3.h
@@ -39,6 +39,9 @@ extern "C" {
 dc_status_t
 hw_ostc3_device_open (dc_device_t **device, dc_context_t *context, const char *name);
 
+dc_status_t
+hw_ostc3_device_custom_open (dc_device_t **device, dc_context_t *context, dc_serial_t *serial);
+
 dc_status_t
 hw_ostc3_device_version (dc_device_t *device, unsigned char data[], unsigned int size);
 
diff --git a/src/hw_ostc3.c b/src/hw_ostc3.c
index adf2ded..eebda24 100644
--- a/src/hw_ostc3.c
+++ b/src/hw_ostc3.c
@@ -295,10 +295,10 @@ hw_ostc3_device_open (dc_device_t **out, dc_context_t *context, const char *name
 
 	// Open the device.
 	int rc = dc_serial_native_open (&device->serial, context, name);
-	if (rc == -1) {
+	if (rc != DC_STATUS_SUCCESS) {
 		ERROR (context, "Failed to open the serial port.");
 		free (device);
-		return DC_STATUS_IO;
+		return rc;
 	}
 
 	// Set the serial communication protocol (115200 8N1).
@@ -330,6 +330,59 @@ hw_ostc3_device_open (dc_device_t **out, dc_context_t *context, const char *name
 }
 
 
+dc_status_t
+hw_ostc3_device_custom_open (dc_device_t **out, dc_context_t *context, dc_serial_t *serial)
+{
+	if (out == NULL || serial == NULL || serial->port == NULL)
+		return DC_STATUS_INVALIDARGS;
+
+	// Allocate memory.
+	hw_ostc3_device_t *device = (hw_ostc3_device_t *) malloc (sizeof (hw_ostc3_device_t));
+	if (device == NULL) {
+		ERROR (context, "Failed to allocate memory.");
+		return DC_STATUS_NOMEMORY;
+	}
+
+	// Initialize the base class.
+	device_init (&device->base, context, &hw_ostc3_device_vtable);
+
+	// Set the default values.
+	memset (device->fingerprint, 0, sizeof (device->fingerprint));
+
+	// Set the serial reference
+	device->serial = serial;
+
+	if (serial->type == DC_TRANSPORT_SERIAL) {
+		// Set the serial communication protocol (115200 8N1).
+		int rc = serial_configure (device->serial->port, 115200, 8, SERIAL_PARITY_NONE, 1, SERIAL_FLOWCONTROL_NONE);
+		if (rc == -1) {
+			ERROR (context, "Failed to set the terminal attributes.");
+			device->serial->ops->close (device->serial->port);
+			free (device);
+			return DC_STATUS_IO;
+		}
+	}
+
+	// Set the timeout for receiving data (3000ms).
+	if (serial_set_timeout (device->serial->port, 3000) == -1) {
+		ERROR (context, "Failed to set the timeout.");
+		device->serial->ops->close (device->serial->port);
+		free (device);
+		return DC_STATUS_IO;
+	}
+
+	// Make sure everything is in a sane state.
+	serial_sleep (device->serial->port, 300);
+	device->serial->ops->flush (device->serial->port, SERIAL_QUEUE_BOTH);
+
+	device->state = OPEN;
+
+	*out = (dc_device_t *) device;
+
+	return DC_STATUS_SUCCESS;
+}
+
+
 static dc_status_t
 hw_ostc3_device_init_download (hw_ostc3_device_t *device)
 {