Develop Reference

(Micro)Python UART response ends with "#Eg[" or adds characters

from machine import Pin, I2C, UART
import utime
from ustruct import unpack
import time
checkCardCmd = bytes([0xff,0x00,0x01,0x83,0x84])
getFirmwareVersionCmd = bytes([0xff,0x00,0x01,0x81,0x82])
uart = UART(1, baudrate=19200, bits=8, parity=None, stop=1)
while True:
# Check if card is present
uart.write(checkCardCmd)
val = uart.read()
print(val)
utime.sleep_ms(250)
When a card is presented on the NFC reader I get this back from val b'\xff\x00\x06\x83\x02\x01#Eg['
This is the reply to the checkCardCmd. I have no clue why it ends with #Eg[ also the reply for no card found comes back as b'\xff\x00\x02\x83N\xd3' notice the N character on the 4th byte, that should just be x83.
Baud Rate is correct and with similar code in NodeJS I get the proper response from UART without the extra N or #Eg]
What am I missing here?

Raspberry PI Writing CSV Python

As part of a project, I am trying to use a Raspberry PI to capture WiFi networks and write it to a CSV file. If the quality of the signal is over 30/70 I want to capture all WiFi SSIDs and their relevant MAC address and record it.
The issue seems to be relevant syntax but I cannot seem to figure out what is wrong.
def wifiscan():
ssid = []
scanoutput = check_output(["iwlist", "wlan0", "scan"])
curtime = time.strftime("%I:%M:%S")
ssid.append(curtime)
for line in scanoutput.split():
line=str(line)
if line.startswith("Quality"):
line=line[8:-25]
if(line>30 and line.startswith("ESSID")
line=line[7:-1]
ssid.append(line)
with open('/home/pi/Desktop/Project/Results/'+'test.csv','a') as csvfile:
csvwriter = csv.writer(csvfile,delimiter=',')
csvwriter.writerow(ssid)
print ssid
Update 1:
Update 2:

I made some changes to your code but i don't know exactaly what you want to accomplish nor what errors you are experiencing, I just fixed some logic an sintax.
As it is, the code will append the ssid data to your csv only if quality is better than 30.
Let me know if that is what you want.
def wifiscan():
ssid = []
scanoutput = check_output(["iwlist", "wlan0", "scan"])
curtime = time.strftime("%I:%M:%S")
ssid.append(curtime)
quality = 0
essid = ""
for line in scanoutput.split('\n'):
line=str(line)
if line.startswith("Quality"):
quality=int(line[8:-25])
if quality>30 and line.startswith("ESSID"):
line=line[7:-1]
ssid.append(quality)
ssid.append(line)
with open('/home/pi/Desktop/Project/Results/'+'test.csv','a') as csvfile:
csvwriter = csv.writer(csvfile,delimiter=',')
csvwriter.writerow(ssid)
print ssid
Note that the code is sensible to any change in the sintax of the input you provide.
Also, to avoid syntax change issues in your input, maybe you should read about regular expressions in python: https://docs.python.org/2/howto/regex.html

Python Socket Wireless scan strange output

i have this code here:
import socket
raw = socket.socket(socket.AF_PACKET, socket.SOCK_RAW, socket.htons(0x0003))
raw.bind(("mon0", 0x0003))
ap_list = set()
out = open("out.cap", 'w')
while True:
pkt = raw.recvfrom(2048)[0]
if pkt[36:42] not in ap_list:
ap_list.add(pkt[36:42])
print (pkt)
out.writelines(str(pkt))
but the output is kinda strange to me. how to make it Human readable?
Example of output:
b'\x00!c\xf60\xbe\x807s\xa8\xe5#\x08\x00E\x00\x004\xea\xec#\x00$\x06\xd2\xcck\x15mA\xc0\xa8\x00\x0c\x00P\x90\xee\x9dx\xd9E=\xfd;[\x80\x10\x00no\xc0\x00\x00\x01\x01\x08\n)\xa0w\x10\x00\xd6J\xa8'
Update:
using this
decoded = pkt.decode("ISO-8859-1")
i've managed to do what i need but wireshark don't read my output file very well and i also need to remove useless data from the output
some help?
this is the new code:
import socket
import sys
raw = socket.socket(socket.AF_PACKET, socket.SOCK_RAW, socket.htons(0x0003))
raw.bind((sys.argv[1], 0x0003))
ap_list = set()
out = open("out.cap", 'w')
while True:
pkt = raw.recvfrom(1024)[0]
if pkt[36:42] not in ap_list:
ap_list.add(pkt[36:42])
decoded = pkt.decode("ISO-8859-1")
print(str(pkt[0:20]).split("'")[1])
out.writelines(str(decoded) + "\n")

In Wireshark you should be able to see what protocols are being used. Then you can parse them, for example using the scapy package.
– John Zwinck

Reading bytes from ser.read()

I have one XBee router (XB-X) connected to an ultrasonic range sensor and the other XBee coordinator (XB-Y) connected to my PC. XB-X will send the sensor reading to XB-Y. I am trying to extract the bytes from ser.read() on my PC using Python.
I got a weird bytes of string consist of ">>~}3#zi167.89" on output, may I know how to extract only the floating point number (167.89 in this example)? The number of bytes are specified by setting ser.read(size=xx). Is there any alternative way of doing it?
import serial
import zigbee
from xbee import ZigBee
import re
ser = serial.Serial("COM4", 9600)
while True:
try:
input = ser.read(20)
m = re.search(r'(\d+\.\d+)', input)
if m:
num = m.group()
# statements...
It is working now, carelessly typed 'group' as 'groups'.

Just use a regular expression:
import re
input = ser.read()
m = re.search(r'(?P<num>\d+\.\d+)', input)
if m:
num = float(m.group('num'))

Problem reading data from serial port in python

I have a python program that is trying to read 14 bytes from a serial port that
are arriving very slowly. I want want to capture all of the bytes in a
bytearray[14]. I understand there are new byte array features in python 3.0, but
I'm only running python 2.6.6. Upgrading may have unexpected consequences so I have to
stick with 2.6.6.
Data only intermittently flows over the serial port. I get one message on the
port maybe every 2 minutes or so. This data flows very slowly. The problem I am seeing is
that my code does not relaibly read the data one byte at a time. I want to frame this
data at exactly 14 bytes, then process the data and start fresh with a new 14
bytes.
Am I taking the wrong approach here? Advice?
ser = serial.Serial('/dev/ttyUSB1', 1200, timeout=0)
ser.open()
print "connected to: " + ser.portstr
count=0
while True:
line =ser.readline(size=14) # should block, not take anything less than 14 bytes
if line:
# Here I want to process 14 bytes worth of data and have
# the data be consistent.
print "line(" + str(count) + ")=" + line
count=count+1
ser.close()
Here's what I'm expecting: line(1)=� 0~ 888.ABC� /ends in carriage return
----------begin output------
line(0)=0
line(1)=~ ??1. ABC � # here get some multiple bytes and stuff gets out of synch
�ine(2)=
line(3)=0
line(4)=~
line(5)=
line(6)=8
line(7)=8
line(8)=8
line(9)=.
line(10)=
line(11)=A
line(12)=B
line(13)=C
line(14)=
line(15)=�
line(16)=
#...
line(48)=
line(49)=�
line(50)=0
line(51)=~
line(52)=
line(53)=8
line(54)=8
line(55)=8
line(56)=.
line(57)=
line(58)=A
line(59)=B
line(60)=C
line(61)=
line(62)=�
line(63)=
line(64)=
----------end output------

The API documentation for PySerial says readline() reads until \n, or until size is reached. However, the read() function says it will block until size is reached. Both of these functions say they will return early if a timeout is set.
Possible values for the parameter timeout:
timeout = None: wait forever
timeout = 0: non-blocking mode (return immediately on read)
timeout = x: set timeout to x seconds (float allowed)
Maybe try timeout=None instead of timeout=0

Try this:
ser = Serial('/dev/ttyUSB1', 1200, timeout=0)
print "connected to: " + ser.portstr
count=0
while True:
for line in ser.readlines()
print "line(" + str(count) + ")=" + line
count=count+1
ser.close()
You might also be interested in the line.strip() function if you haven't used it. Also, emphasis on the s in ser.readlines(), different from .readline().

Change the baudrate.
ser = serial.Serial('/dev/ttyUSB1', 9600, timeout=0)
to a compatible baudrate.
For getting 14 byte data :
data = ser.read(size=14)