Question

我一直在代码中使用pySerial 3.4从串行端口（确切地说是RFID芯片读取器/写入器）提取数据。我需要向阅读器发送命令，然后从阅读器中读取结果。

基本上，我正在编写12个字节的命令，然后尝试接收24个字节的输出。我的问题是：为什么port.read(24)无法工作，但是res = bytearray(24); port.readinto(res);成功地工作？随附完整代码：

import serial

ser = serial.Serial('COM5',9600,timeout=5,rtscts=True,inter_byte_timeout=5)

def compose_find(port):
    port.write(bytes.fromhex('555500000003020405'))
    port.flush()
    return port.read(12)[6] == 0

def compose_read(port,sec_loc=0,block_loc=0,key='F'*12):
    assert sec_loc in range(0,16),'sector location is from 0~15'
    assert block_loc in range(0,4),'block location is from 0~3'
    assert compose_find(port),'cannot read card!'

    sec_loc = '0'+str(hex(sec_loc))[2:]
    block_loc = '0'+str(hex(block_loc))[2:]
    command = '55 55 00 00 00 0E 03 07 00 00 {} {} 60 
        {}'.format(sec_loc,block_loc,key).replace(' ','')
    parity = str(hex(reduce(lambda x,y:x^y,bytes.fromhex(command))))[2:]
    if len(parity) == 1:  parity = '0'+parity
    command += parity
    print(command)
    port.write(bytes.fromhex(command))
    port.flush()
    res = bytearray(24)
    port.readinto(res)
    return res

compose_read(port=ser,sec_loc=8,block_loc=2)

Answer 1

<VirtualHost MY_IP:443> ServerName www.mydomain.com SSLProxyEngine On ErrorLog ${APACHE_LOG_DIR}/error.log CustomLog ${APACHE_LOG_DIR}/access.log combined SSLCertificateFile /etc/letsencrypt/live/mydomain.com/fullchain.pem SSLCertificateKeyFile /etc/letsencrypt/live/mydomain.com/privkey.pem Include /etc/letsencrypt/options-ssl-apache.conf RewriteEngine On RewriteCond %{HTTP:Upgrade} =websocket [NC] RewriteRule /(.*) wss://localhost:8080/$1 [P,L] ProxyPass / http://localhost:8081/ ProxyPassReverse / http://localhost:8081/ </VirtualHost> <VirtualHost localhost:8081> DocumentRoot /var/www/www.mydomain.com/ </VirtualHost>最多读取readinto(buf)个字节并返回，而len(buf)将阻塞，直到接收到read(num)个字节。如果要使num即使没有足够的可用数据也要返回，则在打开端口时必须指定timeout。

PySerial：read（）和readinto（）有什么区别？

1 个答案: