[SOLVED] Decode incoming packets from TinyTX to Raspberry Pi serial in Python

Submitted by ltpitt on Thu, 10/04/2014 - 22:45

Hi everyone!

I am receiving packets from TinyTX node on my raspberry pi and they look like:

Got: 16 166 19 192 12 156 9
-> ack

Got: 16 116 19 164 12 146 9

-> ack

I would like to decode those but...

How?

Some informations are here:

http://jeelabs.org/2010/12/07/binary-packet-decoding/

I've found various way to decipher this encoding in python but I always get incredible (and obviously false) values:

def rread_data(rx):
data = rx.split(" ")
    a = int(data[1])
    b = int(data[2])
    c = int(data[3])
    d = int(data[4])
    e = int(data[5])
    f = int(data[6])
#    node_id = str(int(data[0]) & 0x1f)
    humidity = str((a+b*256)/100.0)
    voltage = str(c+d*256)
    temperature = str((e+f*256)/100.0)
#    print "node:", node_id
    print "humidity:", humidity, "%"
    print "temperature:", temperature, "C"
    print "voltage:", voltage, "mV"

This data is coming from a DHT22 sensor and it should include temp, humidity and voltage...

What can I read to understand better what to do?

Thanks to everyone reading.

Re: [SOLVED] Decode incoming packets from TinyTX to Raspberry Pi serial in Python

Submitted by ukmoose on Thu, 10/04/2014 - 23:29.

I'd start by reading and understanding the code loaded onto the TinyTx.

Re: [SOLVED] Decode incoming packets from TinyTX to Raspberry Pi serial in Python

Submitted by ltpitt on Sun, 13/04/2014 - 18:39.

Here is, for anyone interested, the working function in python:

import serial
import string
from time import sleep
import MySQLdb
import MySQLdb as Database
from warnings import filterwarnings
filterwarnings('ignore', category = Database.Warning)
import smtplib
from email.mime.text import MIMEText

# Specify your serial port path (/dev/ttyAMA0 is default for Raspberry Pi)
serialport = serial.Serial("/dev/ttyAMA0", 9600, timeout=0)

# This function reads data from serial port and prints received values in human readable format
def read_data(rx):

data = rx.lstrip().split(" ")

    a = int(data[1])
    b = int(data[2])
    c = int(data[3])
    d = int(data[4])
    e = int(data[5])
    f = int(data[6])

    node_id = str(int(data[0]) & 0x1f)
    humidity = str((a+b*256)/100.0)
    voltage = str(c+d*256)
    temperature = str((e+f*256)/100.0)
    print "node:", node_id
    print "humidity:", humidity, "%"
    print "temperature:", temperature, "C"
    print "voltage:", voltage, "mV"

try_number = 0

while True:

    data = serialport.read(9999)
    if len(data) > 0:
        print "Got data: "+data
        read_data(data)
    sleep(1)
    try_number += 1
    print 'Waiting data... '+str(try_number)

ser.close()

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