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<title>OpenOCD User’s Guide: OpenOCD Project Setup</title>
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<a name="OpenOCD-Project-Setup"></a>
<div class="header">
<p>
Next: <a href="Config-File-Guidelines.html#Config-File-Guidelines" accesskey="n" rel="next">Config File Guidelines</a>, Previous: <a href="Running.html#Running" accesskey="p" rel="previous">Running</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="OpenOCD-Concept-Index.html#OpenOCD-Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="OpenOCD-Project-Setup-1"></a>
<h2 class="chapter">5 OpenOCD Project Setup</h2>
<p>To use OpenOCD with your development projects, you need to do more than
just connecting the JTAG adapter hardware (dongle) to your development board
and then starting the OpenOCD server.
You also need to configure that server so that it knows
about that adapter and board, and helps your work.
You may also want to connect OpenOCD to GDB, possibly
using Eclipse or some other GUI.
</p>
<a name="Hooking-up-the-JTAG-Adapter"></a>
<h3 class="section">5.1 Hooking up the JTAG Adapter</h3>
<p>Today’s most common case is a dongle with a JTAG cable on one side
(such as a ribbon cable with a 10-pin or 20-pin IDC connector)
and a USB cable on the other.
Instead of USB, some cables use Ethernet;
older ones may use a PC parallel port, or even a serial port.
</p>
<ol>
<li> <em>Start with power to your target board turned off</em>,
and nothing connected to your JTAG adapter.
If you’re particularly paranoid, unplug power to the board.
It’s important to have the ground signal properly set up,
unless you are using a JTAG adapter which provides
galvanic isolation between the target board and the
debugging host.
</li><li> <em>Be sure it’s the right kind of JTAG connector.</em>
If your dongle has a 20-pin ARM connector, you need some kind
of adapter (or octopus, see below) to hook it up to
boards using 14-pin or 10-pin connectors ... or to 20-pin
connectors which don’t use ARM’s pinout.
<p>In the same vein, make sure the voltage levels are compatible.
Not all JTAG adapters have the level shifters needed to work
with 1.2 Volt boards.
</p>
</li><li> <em>Be certain the cable is properly oriented</em> or you might
damage your board. In most cases there are only two possible
ways to connect the cable.
Connect the JTAG cable from your adapter to the board.
Be sure it’s firmly connected.
<p>In the best case, the connector is keyed to physically
prevent you from inserting it wrong.
This is most often done using a slot on the board’s male connector
housing, which must match a key on the JTAG cable’s female connector.
If there’s no housing, then you must look carefully and
make sure pin 1 on the cable hooks up to pin 1 on the board.
Ribbon cables are frequently all grey except for a wire on one
edge, which is red. The red wire is pin 1.
</p>
<p>Sometimes dongles provide cables where one end is an “octopus” of
color coded single-wire connectors, instead of a connector block.
These are great when converting from one JTAG pinout to another,
but are tedious to set up.
Use these with connector pinout diagrams to help you match up the
adapter signals to the right board pins.
</p>
</li><li> <em>Connect the adapter’s other end</em> once the JTAG cable is connected.
A USB, parallel, or serial port connector will go to the host which
you are using to run OpenOCD.
For Ethernet, consult the documentation and your network administrator.
<p>For USB based JTAG adapters you have an easy sanity check at this point:
does the host operating system see the JTAG adapter? If that host is an
MS-Windows host, you’ll need to install a driver before OpenOCD works.
</p>
</li><li> <em>Connect the adapter’s power supply, if needed.</em>
This step is primarily for non-USB adapters,
but sometimes USB adapters need extra power.
</li><li> <em>Power up the target board.</em>
Unless you just let the magic smoke escape,
you’re now ready to set up the OpenOCD server
so you can use JTAG to work with that board.
</li></ol>
<p>Talk with the OpenOCD server using
telnet (<code>telnet localhost 4444</code> on many systems) or GDB.
See <a href="GDB-and-OpenOCD.html#GDB-and-OpenOCD">GDB and OpenOCD</a>.
</p>
<a name="Project-Directory"></a>
<h3 class="section">5.2 Project Directory</h3>
<p>There are many ways you can configure OpenOCD and start it up.
</p>
<p>A simple way to organize them all involves keeping a
single directory for your work with a given board.
When you start OpenOCD from that directory,
it searches there first for configuration files, scripts,
files accessed through semihosting,
and for code you upload to the target board.
It is also the natural place to write files,
such as log files and data you download from the board.
</p>
<a name="Configuration-Basics"></a>
<h3 class="section">5.3 Configuration Basics</h3>
<p>There are two basic ways of configuring OpenOCD, and
a variety of ways you can mix them.
Think of the difference as just being how you start the server:
</p>
<ul>
<li> Many <samp>-f file</samp> or <samp>-c command</samp> options on the command line
</li><li> No options, but a <em>user config file</em>
in the current directory named <samp>openocd.cfg</samp>
</li></ul>
<p>Here is an example <samp>openocd.cfg</samp> file for a setup
using a Signalyzer FT2232-based JTAG adapter to talk to
a board with an Atmel AT91SAM7X256 microcontroller:
</p>
<div class="example">
<pre class="example">source [find interface/signalyzer.cfg]
# GDB can also flash my flash!
gdb_memory_map enable
gdb_flash_program enable
source [find target/sam7x256.cfg]
</pre></div>
<p>Here is the command line equivalent of that configuration:
</p>
<div class="example">
<pre class="example">openocd -f interface/signalyzer.cfg \
-c "gdb_memory_map enable" \
-c "gdb_flash_program enable" \
-f target/sam7x256.cfg
</pre></div>
<p>You could wrap such long command lines in shell scripts,
each supporting a different development task.
One might re-flash the board with a specific firmware version.
Another might set up a particular debugging or run-time environment.
</p>
<blockquote>
<p><b>Important:</b> At this writing (October 2009) the command line method has
problems with how it treats variables.
For example, after <samp>-c "set VAR value"</samp>, or doing the
same in a script, the variable <var>VAR</var> will have no value
that can be tested in a later script.
</p></blockquote>
<p>Here we will focus on the simpler solution: one user config
file, including basic configuration plus any TCL procedures
to simplify your work.
</p>
<a name="User-Config-Files"></a>
<h3 class="section">5.4 User Config Files</h3>
<a name="index-config-file_002c-user"></a>
<a name="index-user-config-file"></a>
<a name="index-config-file_002c-overview"></a>
<p>A user configuration file ties together all the parts of a project
in one place.
One of the following will match your situation best:
</p>
<ul>
<li> Ideally almost everything comes from configuration files
provided by someone else.
For example, OpenOCD distributes a <samp>scripts</samp> directory
(probably in <samp>/usr/share/openocd/scripts</samp> on Linux).
Board and tool vendors can provide these too, as can individual
user sites; the <samp>-s</samp> command line option lets you say
where to find these files. (See <a href="Running.html#Running">Running</a>.)
The AT91SAM7X256 example above works this way.
<p>Three main types of non-user configuration file each have their
own subdirectory in the <samp>scripts</samp> directory:
</p>
<ol>
<li> <b>interface</b> – one for each different debug adapter;
</li><li> <b>board</b> – one for each different board
</li><li> <b>target</b> – the chips which integrate CPUs and other JTAG TAPs
</li></ol>
<p>Best case: include just two files, and they handle everything else.
The first is an interface config file.
The second is board-specific, and it sets up the JTAG TAPs and
their GDB targets (by deferring to some <samp>target.cfg</samp> file),
declares all flash memory, and leaves you nothing to do except
meet your deadline:
</p>
<div class="example">
<pre class="example">source [find interface/olimex-jtag-tiny.cfg]
source [find board/csb337.cfg]
</pre></div>
<p>Boards with a single microcontroller often won’t need more
than the target config file, as in the AT91SAM7X256 example.
That’s because there is no external memory (flash, DDR RAM), and
the board differences are encapsulated by application code.
</p>
</li><li> Maybe you don’t know yet what your board looks like to JTAG.
Once you know the <samp>interface.cfg</samp> file to use, you may
need help from OpenOCD to discover what’s on the board.
Once you find the JTAG TAPs, you can just search for appropriate
target and board
configuration files ... or write your own, from the bottom up.
See <a href="TAP-Declaration.html#autoprobing">Autoprobing</a>.
</li><li> You can often reuse some standard config files but
need to write a few new ones, probably a <samp>board.cfg</samp> file.
You will be using commands described later in this User’s Guide,
and working with the guidelines in the next chapter.
<p>For example, there may be configuration files for your JTAG adapter
and target chip, but you need a new board-specific config file
giving access to your particular flash chips.
Or you might need to write another target chip configuration file
for a new chip built around the Cortex M3 core.
</p>
<blockquote>
<p><b>Note:</b> When you write new configuration files, please submit
them for inclusion in the next OpenOCD release.
For example, a <samp>board/newboard.cfg</samp> file will help the
next users of that board, and a <samp>target/newcpu.cfg</samp>
will help support users of any board using that chip.
</p></blockquote>
</li><li> You may may need to write some C code.
It may be as simple as a supporting a new ft2232 or parport
based adapter; a bit more involved, like a NAND or NOR flash
controller driver; or a big piece of work like supporting
a new chip architecture.
</li></ul>
<p>Reuse the existing config files when you can.
Look first in the <samp>scripts/boards</samp> area, then <samp>scripts/targets</samp>.
You may find a board configuration that’s a good example to follow.
</p>
<p>When you write config files, separate the reusable parts
(things every user of that interface, chip, or board needs)
from ones specific to your environment and debugging approach.
</p><ul>
<li> For example, a <code>gdb-attach</code> event handler that invokes
the <code>reset init</code> command will interfere with debugging
early boot code, which performs some of the same actions
that the <code>reset-init</code> event handler does.
</li><li> Likewise, the <code>arm9 vector_catch</code> command (or
<a name="index-vector_005fcatch"></a>
its siblings <code>xscale vector_catch</code>
and <code>cortex_m vector_catch</code>) can be a timesaver
during some debug sessions, but don’t make everyone use that either.
Keep those kinds of debugging aids in your user config file,
along with messaging and tracing setup.
(See <a href="Architecture-and-Core-Commands.html#softwaredebugmessagesandtracing">Software Debug Messages and Tracing</a>.)
</li><li> You might need to override some defaults.
For example, you might need to move, shrink, or back up the target’s
work area if your application needs much SRAM.
</li><li> TCP/IP port configuration is another example of something which
is environment-specific, and should only appear in
a user config file. See <a href="Daemon-Configuration.html#tcpipports">TCP/IP Ports</a>.
</li></ul>
<a name="Project_002dSpecific-Utilities"></a>
<h3 class="section">5.5 Project-Specific Utilities</h3>
<p>A few project-specific utility
routines may well speed up your work.
Write them, and keep them in your project’s user config file.
</p>
<p>For example, if you are making a boot loader work on a
board, it’s nice to be able to debug the “after it’s
loaded to RAM” parts separately from the finicky early
code which sets up the DDR RAM controller and clocks.
A script like this one, or a more GDB-aware sibling,
may help:
</p>
<div class="example">
<pre class="example">proc ramboot { } {
# Reset, running the target's "reset-init" scripts
# to initialize clocks and the DDR RAM controller.
# Leave the CPU halted.
reset init
# Load CONFIG_SKIP_LOWLEVEL_INIT version into DDR RAM.
load_image u-boot.bin 0x20000000
# Start running.
resume 0x20000000
}
</pre></div>
<p>Then once that code is working you will need to make it
boot from NOR flash; a different utility would help.
Alternatively, some developers write to flash using GDB.
(You might use a similar script if you’re working with a flash
based microcontroller application instead of a boot loader.)
</p>
<div class="example">
<pre class="example">proc newboot { } {
# Reset, leaving the CPU halted. The "reset-init" event
# proc gives faster access to the CPU and to NOR flash;
# "reset halt" would be slower.
reset init
# Write standard version of U-Boot into the first two
# sectors of NOR flash ... the standard version should
# do the same lowlevel init as "reset-init".
flash protect 0 0 1 off
flash erase_sector 0 0 1
flash write_bank 0 u-boot.bin 0x0
flash protect 0 0 1 on
# Reboot from scratch using that new boot loader.
reset run
}
</pre></div>
<p>You may need more complicated utility procedures when booting
from NAND.
That often involves an extra bootloader stage,
running from on-chip SRAM to perform DDR RAM setup so it can load
the main bootloader code (which won’t fit into that SRAM).
</p>
<p>Other helper scripts might be used to write production system images,
involving considerably more than just a three stage bootloader.
</p>
<a name="Target-Software-Changes"></a>
<h3 class="section">5.6 Target Software Changes</h3>
<p>Sometimes you may want to make some small changes to the software
you’re developing, to help make JTAG debugging work better.
For example, in C or assembly language code you might
use <code>#ifdef JTAG_DEBUG</code> (or its converse) around code
handling issues like:
</p>
<ul>
<li> <b>Watchdog Timers</b>...
Watchog timers are typically used to automatically reset systems if
some application task doesn’t periodically reset the timer. (The
assumption is that the system has locked up if the task can’t run.)
When a JTAG debugger halts the system, that task won’t be able to run
and reset the timer ... potentially causing resets in the middle of
your debug sessions.
<p>It’s rarely a good idea to disable such watchdogs, since their usage
needs to be debugged just like all other parts of your firmware.
That might however be your only option.
</p>
<p>Look instead for chip-specific ways to stop the watchdog from counting
while the system is in a debug halt state. It may be simplest to set
that non-counting mode in your debugger startup scripts. You may however
need a different approach when, for example, a motor could be physically
damaged by firmware remaining inactive in a debug halt state. That might
involve a type of firmware mode where that "non-counting" mode is disabled
at the beginning then re-enabled at the end; a watchdog reset might fire
and complicate the debug session, but hardware (or people) would be
protected.<a name="DOCF1" href="#FOOT1"><sup>1</sup></a>
</p>
</li><li> <b>ARM Semihosting</b>...
<a name="index-ARM-semihosting"></a>
When linked with a special runtime library provided with many
toolchains<a name="DOCF2" href="#FOOT2"><sup>2</sup></a>,
your target code can use I/O facilities on the debug host. That library
provides a small set of system calls which are handled by OpenOCD.
It can let the debugger provide your system console and a file system,
helping with early debugging or providing a more capable environment
for sometimes-complex tasks like installing system firmware onto
NAND or SPI flash.
</li><li> <b>ARM Wait-For-Interrupt</b>...
Many ARM chips synchronize the JTAG clock using the core clock.
Low power states which stop that core clock thus prevent JTAG access.
Idle loops in tasking environments often enter those low power states
via the <code>WFI</code> instruction (or its coprocessor equivalent, before ARMv7).
<p>You may want to <em>disable that instruction</em> in source code,
or otherwise prevent using that state,
to ensure you can get JTAG access at any time.<a name="DOCF3" href="#FOOT3"><sup>3</sup></a>
For example, the OpenOCD <code>halt</code> command may not
work for an idle processor otherwise.
</p>
</li><li> <b>Delay after reset</b>...
Not all chips have good support for debugger access
right after reset; many LPC2xxx chips have issues here.
Similarly, applications that reconfigure pins used for
JTAG access as they start will also block debugger access.
<p>To work with boards like this, <em>enable a short delay loop</em>
the first thing after reset, before "real" startup activities.
For example, one second’s delay is usually more than enough
time for a JTAG debugger to attach, so that
early code execution can be debugged
or firmware can be replaced.
</p>
</li><li> <b>Debug Communications Channel (DCC)</b>...
Some processors include mechanisms to send messages over JTAG.
Many ARM cores support these, as do some cores from other vendors.
(OpenOCD may be able to use this DCC internally, speeding up some
operations like writing to memory.)
<p>Your application may want to deliver various debugging messages
over JTAG, by <em>linking with a small library of code</em>
provided with OpenOCD and using the utilities there to send
various kinds of message.
See <a href="Architecture-and-Core-Commands.html#softwaredebugmessagesandtracing">Software Debug Messages and Tracing</a>.
</p>
</li></ul>
<a name="Target-Hardware-Setup"></a>
<h3 class="section">5.7 Target Hardware Setup</h3>
<p>Chip vendors often provide software development boards which
are highly configurable, so that they can support all options
that product boards may require. <em>Make sure that any
jumpers or switches match the system configuration you are
working with.</em>
</p>
<p>Common issues include:
</p>
<ul>
<li> <b>JTAG setup</b> ...
Boards may support more than one JTAG configuration.
Examples include jumpers controlling pullups versus pulldowns
on the nTRST and/or nSRST signals, and choice of connectors
(e.g. which of two headers on the base board,
or one from a daughtercard).
For some Texas Instruments boards, you may need to jumper the
EMU0 and EMU1 signals (which OpenOCD won’t currently control).
</li><li> <b>Boot Modes</b> ...
Complex chips often support multiple boot modes, controlled
by external jumpers. Make sure this is set up correctly.
For example many i.MX boards from NXP need to be jumpered
to "ATX mode" to start booting using the on-chip ROM, when
using second stage bootloader code stored in a NAND flash chip.
<p>Such explicit configuration is common, and not limited to
booting from NAND. You might also need to set jumpers to
start booting using code loaded from an MMC/SD card; external
SPI flash; Ethernet, UART, or USB links; NOR flash; OneNAND
flash; some external host; or various other sources.
</p>
</li><li> <b>Memory Addressing</b> ...
Boards which support multiple boot modes may also have jumpers
to configure memory addressing. One board, for example, jumpers
external chipselect 0 (used for booting) to address either
a large SRAM (which must be pre-loaded via JTAG), NOR flash,
or NAND flash. When it’s jumpered to address NAND flash, that
board must also be told to start booting from on-chip ROM.
<p>Your <samp>board.cfg</samp> file may also need to be told this jumper
configuration, so that it can know whether to declare NOR flash
using <code>flash bank</code> or instead declare NAND flash with
<code>nand device</code>; and likewise which probe to perform in
its <code>reset-init</code> handler.
</p>
<p>A closely related issue is bus width. Jumpers might need to
distinguish between 8 bit or 16 bit bus access for the flash
used to start booting.
</p>
</li><li> <b>Peripheral Access</b> ...
Development boards generally provide access to every peripheral
on the chip, sometimes in multiple modes (such as by providing
multiple audio codec chips).
This interacts with software
configuration of pin multiplexing, where for example a
given pin may be routed either to the MMC/SD controller
or the GPIO controller. It also often interacts with
configuration jumpers. One jumper may be used to route
signals to an MMC/SD card slot or an expansion bus (which
might in turn affect booting); others might control which
audio or video codecs are used.
</li></ul>
<p>Plus you should of course have <code>reset-init</code> event handlers
which set up the hardware to match that jumper configuration.
That includes in particular any oscillator or PLL used to clock
the CPU, and any memory controllers needed to access external
memory and peripherals. Without such handlers, you won’t be
able to access those resources without working target firmware
which can do that setup ... this can be awkward when you’re
trying to debug that target firmware. Even if there’s a ROM
bootloader which handles a few issues, it rarely provides full
access to all board-specific capabilities.
</p>
<div class="footnote">
<hr>
<h4 class="footnotes-heading">Footnotes</h4>
<h3><a name="FOOT1" href="#DOCF1">(1)</a></h3>
<p>Note that many systems support a "monitor mode" debug
that is a somewhat cleaner way to address such issues. You can think of
it as only halting part of the system, maybe just one task,
instead of the whole thing.
At this writing, January 2010, OpenOCD based debugging does not support
monitor mode debug, only "halt mode" debug.</p>
<h3><a name="FOOT2" href="#DOCF2">(2)</a></h3>
<p>See chapter 8 "Semihosting" in
<a href="http://infocenter.arm.com/help/topic/com.arm.doc.dui0203i/DUI0203I_rvct_developer_guide.pdf">ARM DUI 0203I</a>, the "RealView Compilation Tools Developer Guide".
The CodeSourcery EABI toolchain also includes a semihosting library.</p>
<h3><a name="FOOT3" href="#DOCF3">(3)</a></h3>
<p>As a more
polite alternative, some processors have special debug-oriented
registers which can be used to change various features including
how the low power states are clocked while debugging.
The STM32 DBGMCU_CR register is an example; at the cost of extra
power consumption, JTAG can be used during low power states.</p>
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