diff --git a/Sources/SwiftRPLidar/LidarSerial.swift b/Sources/SwiftRPLidar/LidarSerial.swift
index e1b1c38..80f9811 100644
--- a/Sources/SwiftRPLidar/LidarSerial.swift
+++ b/Sources/SwiftRPLidar/LidarSerial.swift
@@ -1,8 +1,10 @@
+import Foundation
+
 protocol LidarSerial {
     var dtr: Bool {get set};
     var inWaiting: Int {get};
     func closePort() -> Void;
     func openPort() -> Void;
-    readData(ofLength: Int) throws -> Void;
-    writeData(_ data: Data) throws -> Void;
+    func readData(ofLength: Int) throws -> Data;
+    func writeData(_ data: Data) throws -> Void;
 }
diff --git a/Sources/SwiftRPLidar/SwiftRPLidar.swift b/Sources/SwiftRPLidar/SwiftRPLidar.swift
index 4b858a0..d476c9d 100644
--- a/Sources/SwiftRPLidar/SwiftRPLidar.swift
+++ b/Sources/SwiftRPLidar/SwiftRPLidar.swift
@@ -1,5 +1,4 @@
 import Foundation
-import LidarSerial
 
 struct Constants{
     static let SYNC: UInt8 = 0xA5