m65dbg

An enhanced remote serial debugger/monitor for the mega65 project

• Provide disassembly of output from remote serial output
• Can display your source-code as you debug
  • This requires that you build your assembly source via a modified version of Ophis that enhances the *.list file output
    • git clone https://github.com/gardners/Ophis.git
• allows uploading of a local file directly into mega65 memory via the load command
• allows dumping out of data to a local file via the save command
• Use the back command to get a backstrace of the stack, then use up and down to navigate through the stack
• Many commands can take symbolic references if you tell the Ophis compiler to save out a .map files

Future Wishlist

• How about live assembly, direct into the mega65's memory?

The raw monitor

The m65dbg app adds enhanced commands on-top of the existing commands provided by the raw monitor.

Documentation for this raw monitor exists for it in the following locations:

• C65GS System Notes
  • https://docs.google.com/document/d/1fmEUg6hDdWRb2tFZ3n4LG7S1mNP04_SUAW5DrE8zRpk/edit#
  • See the “4.3 Remote Serial Monitor (handy for debugging)” section
• https://github.com/Ben-401/c65gs/blob/dockit/doc/monitor.md
  • Some extra usage info exists in this page of Ben's fork of the github repo
• Typing “?” within the monitor (via your terminal app) to see a list of slightly outdated commands

The source for the m65dbg app is available here:

• https://github.com/MEGA65/m65dbg

Building

• You will need to install a few pre-requisite libraries (via apt-get/yum/zypper, or cygwin's setup.exe)
  • libreadline-devel
• git clone https://github.com/MEGA65/m65dbg
• cd m65dbg
• make
  • This will produce the “m65dbg” executable (or, “m65dbg.exe”, in Cygwin's case)

Walkthrough

For a youtube video walkthrough, please visit:

• https://www.youtube.com/watch?v=2VT8yB3odhg

Here's some written points below:

• Should build fine in Windows+Cygwin and Linux.
• Mac OSX presently doesn't support the 2,000,000 bps serial speed. So as an alternative, you can make m65dbg instead talk to the xemu mega65 emulator via a unix socket.
  • More info at:
• Specify your serial port with the "-l" (or "--device) parameter, E.g., "m65dbg -l /dev/ttyUSB1"

Try the following steps:

• ./m65dbg -l /dev/ttyUSB1
• r (to print out current registers)
• b = a raw command to set a hardware breakpoint
• t1 (to turn trace mode on, a bit like ctrl-c breaking inside gdb)
• t0 (to turn trace mode off, a bit like doing 'c'/continue in gdb)
• n (my 'next'/step-over command, which uses the hardware's step-into command multiple times, can be very slow)
• s (my 'step-into' command, which just calls the hardware's step-into)
• [ENTER] key will repeat the last command
• finish (my 'step-out-of' command, which calls 'n'/next multiple times, can be very slow, depending on how busy the current function is)
• pb/pw/pd/ps = prints byte/word/dword/string values at the given address
• typing “help” will give you the list of m65dbg commands, while typing “?” will give you the list of raw commands.