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ice-gdb - JTAG ICE frontend for avr-gdb
ice-insight - JTAG ICE frontend for avr-insight
ice-gdb/ice-insight [--debugger debugger] [--capture] [--ignore-intr] [--external]
ice-gdb (respectively ice-insight) starts avr-gdb (respectively avr-insight) and avarice
to do on-chip debugging on Atmel AVR processors using their JTAG-based on-chip debug
facilities, via the Atmel JTAG ICE pod.
The executable for the program being debugged is downloaded to the processor unless the
--capture option is specified. A number of extra commands are available within gdb when
started, see their description in NEW GDB COMMANDS below. Restrictions on debugging with
the JTAG ICE pod are discussed in more detail in DEBUGGING WITH JTAG ICE below.
The arguments passed to avarice include the value of the AVARICE_ARGS environment
variable. This is typically used to specify the serial port to which the JTAG ICE pod is
connected by setting AVARICE_ARGS to "-j <serial port name>".
Specify a different debugger than avr-gdb (or avr-insight). This other debugger
should behave similarly to gdb.
Don't download the executable being debugged to the mote, just interrupt the
current program and assume that it matches the executable passed to ice-gdb. This
is similar to "attaching" to a running program within gdb.
Pass the --ignore-intr option to avarice. The single-step commands in gdb (s, n)
will then "step over" interrupt handlers (i.e., if an interrupt occurs, execution
will resume for the duration of the interrupt).
Do not start avarice. Instead, avr-gdb will attempt to connect to an already
running avarice on port localhost:6423.
NEW GDB COMMANDS
Download executable filename to the Atmel processor and start debugging it (this
replaces the gdb load command).
Connect to a copy of avarice running on port localhost:6423.
DEBUGGING WITH JTAG ICE
The JTAG ICE debugging environment has a few restrictions and changes:
· No "soft" breakpoints, and only three hardware breakpoints. The break command sets
hardware breakpoints. The easiest way to deal with this restriction is to enable and
disable breakpoints as needed.
· Two 1-byte hardware watchpoints (but each hardware watchpoint takes away one hardware
breakpoint). If you set a watchpoint on a variable which takes more than one byte,
execution will be abysmally slow. Instead it is better to do the following:
watch *(char *)&myvariable
which watches the least significant byte of myvariable.
· The Atmel AVR processors have a Harvard architecture (separate code and data buses).
To distinguish data address 0 from code address 0, avr-gdb adds 0x800000 to all data
addresses. Bear this in mind when examining printed pointers, or when passing absolute
addresses to gdb commands.
Extra arguments to pass to avarice at startup.
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