我正在将Python 3.7.5与最新版本的串行库一起使用。我正在尝试通过python和arduino制造RFID身份验证设备。用户必须在连接到arduino的RFID中扫描其ID,并且arduino必须将UID发送到python软件。在我的笔记本电脑中,正在侦听串行的线程正在运行。它检查UID,如果允许则发送“ O”,如果不允许则发送“ X”。在arduino中,程序然后等待是否有数据通过串行发送,然后检查输入是否为'O'。如果RX为'O',则LED必须点亮绿色,否则为红色。
我的问题是,当我第一次扫描正确的uid时,它变成绿色,没有问题。如果我扫描另一个正确的uid,它将再次变为绿色,没问题。如果我扫描一个不正确的uid,它会变成绿色,但是在我的python代码中,它应该是红色的。然后,如果我扫描正确的uid,它将变成红色,而应该是绿色。我尝试为arduino和python添加延迟,以等待先前的输入清除,并且还尝试在传输后没有运气的情况下进行刷新。
tl;博士 arduino输出一个uid扫描结果较晚,我不知道该怎么办。
Python:
# Reads data from the serial monitor without interrupting the main thread
from serial import Serial
import time
from threading import Thread
class SerialListener:
def __init__(self, baudrate=9600, timeout=1):
try:
self.ser = Serial('/dev/ttyACM0', baudrate, timeout=timeout)
except:
self.ser = Serial('/dev/ttyACM1', baudrate, timeout=timeout)
self.stopped = False
self.paused = False
self.stream = ''
time.sleep(1) # Wait for serial buffer to reset
def start(self):
Thread(target=self.update, args=()).start()
return self
def update(self):
if not self.paused:
while True:
if self.stopped:
self.ser.close()
print("Serial Thread Stopped")
print("Serial Port Closed")
break
try:
self.stream = self.ser.readline().decode('utf-8')
except:
self.stream = self.ser.readline().decode('ascii')
self.stream = self.stream.rstrip()
def stop(self):
self.stopped = True
def pause(self):
self.paused = True
def flush(self):
self.ser.flush()
def readDistance(self):
try:
return float(self.stream)
except:
return -1 # Returns -1 if there is an error in reading
def readRFID(self):
return self.stream
def write(self, msg):
self.ser.write(msg.encode())
if __name__ == "__main__": # FOR DEBUGGING ONLY
uno = SerialListener().start()
uno.flush()
print("Serial Started")
uid = ''
while True:
uid = uno.readRFID()
if uid is not '':
uno.flush()
time.sleep(0.1)
if uid == "5BEE9F0D":
uno.write('O')
print("SHOULD BE GREEN")
else:
uno.write('X')
print("SHOULD BE RED")
print(uid)
uno.stop()
Arduino:
#include <MFRC522.h>
#define GREEN_LED 6
#define RED_LED 7
#define BUZZER 8
MFRC522 rfid(10, 9);
unsigned long timer = 0;
bool readStatus = false;
void setup() {
pinMode(RED_LED, OUTPUT);
pinMode(GREEN_LED, OUTPUT);
Serial.begin(9600);
SPI.begin();
rfid.PCD_Init();
for(int i = 0; i < 10; i++)
Serial.write('\n');
delay(5);
digitalWrite(RED_LED, HIGH);
}
void loop() {
while(!readStatus){
if(rfid.PICC_IsNewCardPresent()){
if(rfid.PICC_ReadCardSerial()){
byte uid[rfid.uid.size];
if((millis() - timer) > 1000){
for(int i = 0; i < rfid.uid.size; i++)
uid[i] = rfid.uid.uidByte[i];
for(int i = 0; i < sizeof(uid); i++){
if(uid[i] < 0x10)
Serial.print('0');
Serial.print(uid[i], HEX);
}
Serial.println();
readStatus = true;
timer = millis();
}
Serial.flush();
}
}
}
if(readStatus){
while(!Serial.available());
char rx = 'X';
while(Serial.available()){
rx = Serial.read();
}
if(rx == 'O'){
digitalWrite(GREEN_LED, HIGH);
digitalWrite(RED_LED, LOW);
tone(BUZZER, 2500);
delay(100);
noTone(BUZZER);
readStatus = false;
}
else{
digitalWrite(RED_LED, LOW);
digitalWrite(GREEN_LED, LOW);
tone(BUZZER, 1000);
delay(50);
noTone(BUZZER);
delay(30);
tone(BUZZER, 1000);
delay(50);
noTone(BUZZER);
digitalWrite(RED_LED, HIGH);
readStatus = false;
}
}
}
输出:
Serial Started
SHOULD BE RED
05520320 // it is red
SHOULD BE RED
05520320 // it is red
SHOULD BE GREEN
5BEE9F0D // it is red
SHOULD BE GREEN
5BEE9F0D // it is green
SHOULD BE RED
05520320 // it is green
答案 0 :(得分:0)
好的,我通过修改pyserial的超时并在读取之间增加了1秒的延迟来解决了这个问题。
问题在于,由于我设置条件的方式,pyserial多次写入序列。
while True:
uid = uno.readRFID()
if uid is not '':
uno.flush()
time.sleep(0.1)
if uid == "5BEE9F0D":
uno.write('O')
print("SHOULD BE GREEN")
else:
uno.write('X')
print("SHOULD BE RED")
print(uid)
由于我设置的超时为1,PySerial将继续读取UID直到超时。这将导致uid在1秒钟内不等于”,并且不必要地多次将数据发送到串行。
在Arduino中,它仅从缓冲区读取一个字节的字符,并且在读取后,将从缓冲区读取的字符移除。但是,python不仅向序列发送1个字符,而且多次发送。这就是为什么Arduino从PREVIOUS缓冲区读取字符而不是python发送到串行的新字符时输出不正确的原因
为解决此问题,我减小了超时时间,以便在达到超时时间后清除串行输入。请勿将超时值设置得太低,否则可能无法读取数据。
def __init__(self, baudrate=9600, timeout=0.5):
第二,我在主线程上从串行读取之间添加了一个延迟
uid = ''
while True:
while uid is '':
uid = uno.readRFID()
time.sleep(0.1)
if uid == "5BEE9F0D":
uno.write('O')
else:
uno.write('X')
print(uid)
time.sleep(1)
uid = ''
Arduino的代码可以正常工作,所以我没有改变它,唯一的问题是python代码本身。