#####################################################################################################
# Active RFID with the Wavetrend L-RX300 and Synapse RF Engine
# http://www.ns-tech.co.uk/blog/2011/03/active-rfid-with-the-wavetrend-l-rx300-and-synapse-rf-engine/
#####################################################################################################

from synapse.switchboard import *

#Init
def startup():

    initUart(1, 57600) #Set UART1 to 57600 baud

    #Connect serial port to STDIN
    uniConnect(DS_STDIO, DS_UART1)

@setHook(HOOK_STDIN)
def stdinEvent(data):

    if (len(data) != 0):

        parse(data)

#Convert bytes to hex
def bin2hex(str):

    hex = ""
    count = len(str)
    index = 0
    while index < count:
        byte = ord(str[index])
        hex += bin2hex_nibble(byte >> 4)
        hex += bin2hex_nibble(byte)
        index += 1

    return hex

def bin2hex_nibble(nibble):
    hexStr = "0123456789ABCDEF"
    return hexStr[nibble & 0xF]

#Install event handlers
snappyGen.setHook(SnapConstants.HOOK_STARTUP, startup)

def _nibble_to_dec(s):
    if s >= "0" and s <= "9":
        return ord(s) - ord("0")
    else:
        return ord(s) - ord("A") + 10

def _get_byte(s, i):
    return ord(s[i - 1])

def _sum_bytes(s, i1, i2):
    i = i1
    r = 0
    while i <= i2:
        r = r + ord(s[i - 1])
        i = i + 1
    return r

def parse(s):
    if s[0] != "\x55":
        s = s[1:]

    if len(s) > 28:
        expected_checksum = ord(s[28])
        actual_checksum = (_sum_bytes(s, 9, 10) + _sum_bytes(s, 14, 26)) & 255
        if expected_checksum == actual_checksum:

            logdata = "" \
            "Site: " + bin2hex(s[18:21]) + "\n" \
            "TagID: " + bin2hex(s[21:25]) + "\n" \
            "RSSI: " + str(ord(s[27])) + "\n" \
            "Trig: " + str((not not (ord(s[9]) & 128))) + "\n" \
            "--\n"
            rpc('\x00\x00\x01', 'logEvent', logdata)

            logdata = "" \
            "Age: " + bin2hex(s[13:17]) + "\n" \
            "---------\n"

            rpc('\x00\x00\x01', 'logEvent', logdata)