如何让python的摄像头识别与Arduino之间进行串口通讯？

例如：python通过摄像头实时识别物体，并将结果反馈到arduino上（点亮小灯）

已知的串口通讯如下，如何加入摄像头识别等
Python端：
import cv2
import serial

ser = serial.Serial("COM3", 9600)
cap = cv2.VideoCapture(0, cv2.CAP_DSHOW)
face_cascade = cv2.CascadeClassifier("haarcascade_frontalface_default.xml")

while True:
ret, frame = cap.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
faces = face_cascade.detectMultiScale(gray, 1.3, 5)
key = len(faces)
key2 = str(key)
data = ser.write(key2.encode())
for (x, y, w, h) in faces:
cv2.rectangle(frame, (x, y), (x + w, y + h), (255, 0, 0), 2)
cv2.imshow('test', frame)

if cv2.waitKey(1) & 0xFF == ord('q'):
    break

cap.release()
cv2.destroyAllWindows()

Arduino端：
char data;
void setup() {
Serial.begin(9600);
pinMode(13, OUTPUT);
}
void loop() {
while (Serial.available() > 0)
{
data = Serial.read();
if (data == '1') {
digitalWrite(13, HIGH);
}
else {
digitalWrite(13, LOW);
}
}
delay(30);
}