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181 lines
6.6 KiB
Python
181 lines
6.6 KiB
Python
"""Demonstrates DMPAFT "resend" bug.
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The Davis documentation says that a page can be resent on request, but it
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does not seem to work.
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1/10/2012. According to 'Brett' at Davis, the correct resend code is decimal
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21, not hex 21. Indeed, this seems to fix the problem.
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Requires package "pyserial". This can be downloaded on Debian (Ubuntu) using
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apt-get install python-serial
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To demonstrate the bug, simply run this file:
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python vp_resend_bug.py
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AUTHOR:
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Tom Keffer (tkeffer@gmail.com)
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DATE:
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5-Oct-2011
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"""
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# $Revision$
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# $Author$
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# $Date$
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import serial
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import struct
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import time
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# A few handy constants:
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_ack = chr(0x06)
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_resend = chr(0x21) # 1/10/2012. Should be decimal 21.
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# The time to request for the "DMPAFT" command:
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year = 2011
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month = 10
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day = 05
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hour = 00
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minute = 00
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# Main entry point:
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def main():
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print "Demonstrates resend bug in the DMPAFT command"
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# Open up the port:
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serial_port = serial.Serial("/dev/ttyUSB0", baudrate=19200, timeout=5)
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# Wake it up:
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serial_port.write('\n\n\n')
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# Give it time to react
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time.sleep(0.5)
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# Flush the input
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serial_port.flushInput()
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# Now that we have its attention, look for the formal acknowledgment:
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serial_port.write('\n')
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# Get the response:
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response = serial_port.read(2)
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if response != '\n\r':
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print "Unable to wake up console"
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exit()
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print "Successfully woke up console"
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# Now send the DMPAFT command:
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serial_port.write('DMPAFT\n')
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# Get the response:
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response = serial_port.read(1)
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if response != _ack:
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print "Unable to get ACK from console after sending DMPAFT"
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exit()
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print "Got <ACK> after sending DMPAFT <ACK>"
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# Form the date & time using the Davis format:
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vantageDateStamp = day + (month<<5) + ((year-2000)<<9)
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vantageTimeStamp = hour *100 + minute
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#Pack the date and time into a string, little-endian order
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datestr = struct.pack("<HH", vantageDateStamp, vantageTimeStamp)
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#Calculate the crc for the date:
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crc = crc16(datestr)
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# ...and pack that on to the end of the date string in big-endian order:
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datestr_with_crc = datestr + struct.pack(">H", crc)
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# Write the date string with crc to the port:
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serial_port.write(datestr_with_crc)
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# Look for the acknowledgment.
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response = serial_port.read()
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if response != _ack:
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print "Unable to get <ACK> after sending encoded date/time string"
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exit()
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print "Got <ACK> after sending encoded date/time string"
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# Look for the number of pages that will be sent,
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# the location of the first page, and a 2 byte CRC.
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_buffer = serial_port.read(6)
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# Unpack it (ignore the CRC):
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(_npages, _start_index) = struct.unpack("<HH", _buffer[:4])
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print "DMPAFT says that there will be %d pages with starting index %d" %(_npages, _start_index)
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# Start the download by sending an <ACK>
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serial_port.write(_ack)
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# Download the first page:
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_page = serial_port.read(267)
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# Get the page sequence number:
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_page_no = ord(_page[0])
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print "Successfully downloaded page number %d. Length is %d" % (_page_no, len(_page))
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print "HOWEVER, I will pretend the CRC is in error and ask for it again"
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# Request a resend
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serial_port.write(_resend)
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# Try to read it again. Unfortunately, the console does not respond
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# and the request times out.
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_page = serial_port.read(267)
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if len(_page) == 0:
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print "After asking for resend, an empty buffer was returned."
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else:
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print "No problem after asking for resend! Downloaded page number %d, length is %d" % (_page_no, len(_page))
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#===============================================================================
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# UTILITIES
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#===============================================================================
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import array
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_table=(
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0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, # 0x00
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0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, # 0x08
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0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, # 0x10
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0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de, # 0x18
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0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, # 0x20
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0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, # 0x28
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0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, # 0x30
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0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, # 0x38
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0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823, # 0x40
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0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, # 0x48
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0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, # 0x50
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0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, # 0x58
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0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, # 0x60
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0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49, # 0x68
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0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, # 0x70
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0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, # 0x78
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0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, # 0x80
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0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067, # 0x88
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0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, # 0x90
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0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, # 0x98
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0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, # 0xA0
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0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, # 0xA8
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0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c, # 0xB0
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0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, # 0xB8
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0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab, # 0xC0
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0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, # 0xC8
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0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, # 0xD0
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0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92, # 0xD8
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0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, # 0xE0
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0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, # 0xE8
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0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, # 0xF0
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0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0, # 0xF8
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)
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table = array.array('H',_table)
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def crc16(string, crc=0):
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""" Calculate CRC16 sum"""
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for ch in string:
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crc = (table[((crc>>8)^ord(ch)) & 0xff] ^ (crc<<8)) & 0xffff
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return crc
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# Invoke the entry point:
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main() |