Add main function

This commit adds a main function to the alpaca_isp package, which will
eventually allow flashing microcontrollers from the command line but for
now mostly parses command-line arguments.  There's more work to do
before I can get on with the real flashing (microcontroller-specific
stuff, Intel HEX stuff).

alpaca_isp/__init__.py

 __author__ = "Clayton G. Hobbs"
 __version__ = "0"
 
+import argparse
 import struct
+import sys
 import time
 from enum import Enum
 
 import serial
 
 
+_DEFAULT_BAUDRATE = 115200
+_DEFAULT_CLOCK = 12000
+_DEFAULT_TIMEOUT = 0.1
+
+
 class LPC:
     """Interface for LPC in-system programming"""
 
-    def __init__(self, serport, baudrate=115200, clock=12000, timeout=0.1):
+    def __init__(self, serport, baudrate=_DEFAULT_BAUDRATE,
+            clock=_DEFAULT_CLOCK, timeout=_DEFAULT_TIMEOUT):
         self._serport = serport
         self._baudrate = baudrate
         self._clock = clock
         time.sleep(delay)
         self._uart.rts = False
 
-    def synchronize(self, verbose=False):
-        """Begin communication with the microcontroller"""
+    def synchronize(self, verbose=False, max_tries=None):
+        """Begin communication with the microcontroller
+
+        If verbose is True, prints a . for every synchronization attempt.
+        If max_tries is an integer, attempt to synchronize at most that many
+        times before failing by raising RecvTimeout.
+        """
         # Synchronize with the MCU
         while True:
             # Send a ?
             self._uart.write(b"?")
             self._uart.flush()
             if verbose:
-                print("?")
+                print(".", end="", flush=True)
             # Receive a response
             try:
                 s = self._readline()
             except RecvTimeout:
+                if max_tries is not None:
+                    max_tries -= 1
+                    if max_tries <= 0:
+                        raise
                 continue
             # If we got the right response, break
             if s == b"Synchronized\r\n":
 
 class RecvTimeout(ISPError):
     """Timeout while receiving a command"""
+
+
+def main():
+    """Entry point for Alpaca ISP command line tool"""
+    # Make the argument parser
+    parser = argparse.ArgumentParser(
+            description="Flash an LPC microcontroller")
+    parser.add_argument("file", metavar="file", nargs="+", type=str,
+            help="Intel HEX file to flash to the microcontroller")
+    parser.add_argument("tty", metavar="tty", type=str,
+            help="the tty to which the microcontroller is attached")
+    parser.add_argument("-b", "--baudrate", type=int,
+            default=_DEFAULT_BAUDRATE,
+            help="baud rate used for communication (default: %(default)s)")
+    parser.add_argument("-c", "--clock-khz", type=int, default=_DEFAULT_CLOCK,
+            help="microcontroller's clock frequency in kHz "
+            "(default: %(default)s)")
+    parser.add_argument("-t", "--timeout", type=float,
+            default=_DEFAULT_TIMEOUT,
+            help="timeout for reading data from the microcontroller in "
+            "seconds (default: %(default)s)")
+    parser.add_argument("-e", "--erase", action="store_true",
+            help="erase all the microcontroller's flash before flashing")
+    parser.add_argument("--no-start", action="store_true",
+            help="do not start the microcontroller after flashing")
+    parser.add_argument("--try-sync", type=int,
+            help="maximum number of tries to synchronize with the "
+            "microcontroller")
+    parser.add_argument("--control", action="store_true",
+            help="control RS232 lines to enter ISP mode (/RST = DTR, /ISP = "
+            "RTS)")
+    parser.add_argument("--verify", action="store_true",
+            help="verify that the data were written correctly after flashing")
+
+    # Parse arguments
+    args = parser.parse_args()
+
+    # Open the LPC
+    lpc = LPC(args.tty, baudrate=args.baudrate, clock=args.clock_khz,
+            timeout=args.timeout)
+    lpc.open()
+
+    # Enter ISP mode if we've been asked to do so
+    if args.control:
+        lpc.enter_isp()
+
+    # Synchronize with the microcontroller
+    print("Synchronizing", end="", flush=True)
+    try:
+        lpc.synchronize(max_tries=args.try_sync, verbose=True)
+    except RecvTimeout:
+        print(" failed")
+        sys.exit(1)
+    print()
+
+    # TODO: all the interesting stuff
+
+    lpc.close()

alpaca_isp/__main__.py

+# Copyright 2017 Clayton G. Hobbs
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+# http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Alpaca ISP command line tool"""
+
+import alpaca_isp
+
+if __name__ == "__main__":
+    alpaca_isp.main()