My SHA1 code was returning a different hex digest when I ran it on my Telit GM862 GPS. I eventually tracked the problem down to the hex() function. I found that hex(3181490320L) did not return the right result on my device!

Run this test script and post your results below.

import sys, SER, MDM

# Set up printing to serial
SER.set_speed('115200', '8N1')
class SerWriter:
  def write(self, s):
    SER.send(s + "\r")
sys.stdout = sys.stderr = SerWriter()

# Simplistic AT command function
def at_command(command):
  # Clear the command interface buffer
  MDM.read()
  # Send the command
  MDM.send(command + '\r', 0)
  # Create a buffer
  buffer = ''
  while 1:
    # Listen to serial port for click
    incoming = MDM.receive(1)
    # If we got some data handle it
    if incoming:
      buffer = buffer + incoming
      if buffer.find("OK") > -1:
        return buffer
      elif buffer.find("ERROR") > -1:
        return ''

# Run the tests
print at_command("AT+CGMM")
print at_command("AT+CGMR")
i = 3181490320L
print i
print long(hex(i), 16)

# Restore standard out
sys.stdout = sys.stderr = sys.__stdout__

My output was:

OK

GM862-GPS

OK


07.03.402

OK

3181490320
2376183952

Cheers, Dave.

Edit: In case anyone’s interested here’s my hex() replacement. It’s probably much slower, but it works and can pad the hex string to x bytes.

def write_hex(x, bytes=1):
  h = ['0'] * bytes * 2
  i = 0
  while x > 0:
    if i < bytes * 2:
      h[i] = '0123456789abcdef'[x & 0xf]
    else:
      h.append('0123456789abcdef'[x & 0xf])
    x = x >> 4
    i = i + 1
  h.reverse()
  return ''.join(h)