frontend: enable protocol autodetection by default

It seems to work rather well after some extended testing. Also clean
up and update the protocol documentation while at it.

README.md

@@ -111,18 +111,18 @@ Most importantly, ```-p``` sets the serial port to be used for programming.
 ### Protocols
 
 STC MCUs use a variety of related but incompatible protocols for the
-BSL. The protocol can be specified with the ```-P``` flag. Optionally,
-experimental protocol autodetection can be used. The mapping between
-protocols and MCU series is as follows:
-
-* ```stc89``` STC 89/90 series
-* ```stc12a``` STC12Cx052AD and possibly others
-* ```stc12b``` STC12x52xx series, STC12x56xx series and possibly others
-* ```stc12``` Most STC10/11/12 series (default)
+BSL. The protocol can be specified with the ```-P``` flag. By default
+UART protocol autodetection is used. The mapping between protocols
+and MCU series is as follows:
+
+* ```stc89``` STC89/90 series
+* ```stc12a``` STC12x052 series and possibly others
+* ```stc12b``` STC12x52 series, STC12x56 series and possibly others
+* ```stc12``` Most STC10/11/12 series
 * ```stc15a``` STC15x104E and STC15x204E(A) series
 * ```stc15``` Most STC15 series
 * ```usb15``` USB support on STC15W4 series
-* ```auto``` Automatic detection of UART based protocols
+* ```auto``` Automatic detection of UART based protocols (default)
 
 The text files in the doc/ subdirectory provide an overview over
 the reverse engineered protocols used by the BSLs. For more details,

stcgal/frontend.py

@@ -196,7 +196,7 @@ def cli():
     parser.add_argument("code_image", help="code segment file to flash (BIN/HEX)", type=argparse.FileType("rb"), nargs='?')
     parser.add_argument("eeprom_image", help="eeprom segment file to flash (BIN/HEX)", type=argparse.FileType("rb"), nargs='?')
     parser.add_argument("-a", "--autoreset", help="cycle power automatically by asserting DTR", action="store_true")
-    parser.add_argument("-P", "--protocol", help="protocol version", choices=["stc89", "stc12a", "stc12b", "stc12", "stc15a", "stc15", "usb15", "auto"], default="stc12")
+    parser.add_argument("-P", "--protocol", help="protocol version (default: auto)", choices=["stc89", "stc12a", "stc12b", "stc12", "stc15a", "stc15", "usb15", "auto"], default="auto")
     parser.add_argument("-p", "--port", help="serial port device", default="/dev/ttyUSB0")
     parser.add_argument("-b", "--baud", help="transfer baud rate (default: 19200)", type=BaudType(), default=19200)
     parser.add_argument("-l", "--handshake", help="handshake baud rate (default: 2400)", type=BaudType(), default=2400)