FastApi с потоком

ard.py

@@ -1,12 +1,18 @@
 from serial import Serial
+import threading
 from fastapi import FastAPI
 
-ser = Serial('COM5', 9600)
-s = ser.read(1)       # read up to one hundred bytes
-print(s)
+s=""
+
+ser = Serial('COM4', 9600)
+def pot():
+    global s
+    while True:  
+        s = ser.read(1)       # read up to one hundred bytes
+th=threading.Thread(target=pot)
+th.start()
 app = FastAPI()
 
 @app.get("/")
 async def root():
-    return ("message", s)
-
+    return ("message", s)