[SOLVED] PySerial receiving strange data

Exise · 07-10-2013, 04:02 AM

I've connected an RPi to my smart meter with a serial cable. The smart meter automatically starts sending 20 lines of data, about every 10 seconds.

Smart meter output example data:

Code:

/ISk5\2ME382-1003
0-0:96.1.1(4B414C37303035313039)
1-0:1.8.1(00180.724*kWh)
1-0:1.8.2(00001.416*kWh)
1-0:2.8.1(00000.000*kWh)
1-0:2.8.2(00000.000*kWh)
[...]
!

However, when retrieving the data using PySerial I often get data like this:

Code:

b'\x00\n'
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
\x00\x00\x00\x00\x00\x00\x00\x00

Eventually, I do get some data, but not even all.

My script:

Code:

import sys
import serial

ser = serial.Serial()
ser.baudrate = 9600
ser.bytesize=serial.SEVENBITS
ser.parity=serial.PARITY_EVEN
ser.stopbits=serial.STOPBITS_ONE
ser.xonxoff=0
ser.rtscts=0
ser.timeout=None
ser.port="/dev/ttyUSB0"

ser.open()
count=0
stack=[]
while count < 25:
    p1_raw =  str(ser.readline())
    print(p1_raw)
    count=count+1

ser.close()
exit

The problem seems to be with Python/PySerial. When using cu or minicom the data is received properly.

Is this perhaps a PySerial bug?

gdejonge · 07-12-2013, 07:11 AM

Are you sure you're using the right settings for pyserial. You are using 7E1 while 8N1 is the most used form nowadays.
7E1 means 7 bit data. Even parity. 1 stop bit
8E1 means 8 bit data. No parity . 1 stop bit.

Cheers

Exise · 07-13-2013, 01:10 PM

Quote:

Originally Posted by gdejonge

Are you sure you're using the right settings for pyserial. You are using 7E1 while 8N1 is the most used form nowadays.
7E1 means 7 bit data. Even parity. 1 stop bit
8E1 means 8 bit data. No parity . 1 stop bit.

Cheers

After your post I tried changing various settings. Changing ser.xonxoff=0 to 1 solved the problem. Strange, because others with very similar set-ups did get it working with ser.xonxoff=0. Anyway, thank you!

Settings:

Code:

ser = serial.Serial()
ser.baudrate = 9600
ser.bytesize=serial.SEVENBITS
ser.parity=serial.PARITY_NONE
ser.stopbits=serial.STOPBITS_ONE
ser.xonxoff=1
ser.rtscts=0