Make the doc slightly more complete and add notes on how to add a new target in OpenWrt, some serial console and JTAG tips and tricks
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@13880 3c298f89-4303-0410-b956-a3cf2f4a3e73master
Florian Fainelli
parent
58a5af0afd
commit
7bd4658f08
|
|
@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
|
|||
include $(INCLUDE_DIR)/prereq.mk
|
||||
|
||||
MAIN = openwrt.tex
|
||||
DEPS = $(MAIN) Makefile config.tex network.tex network-scripts.tex network-scripts.tex wireless.tex build.tex adding.tex bugs.tex $(TMP_DIR)/.prereq-docs
|
||||
DEPS = $(MAIN) Makefile config.tex network.tex network-scripts.tex network-scripts.tex wireless.tex build.tex adding.tex bugs.tex debugging.tex $(TMP_DIR)/.prereq-docs
|
||||
|
||||
compile: $(TMP_DIR)/.prereq-docs
|
||||
$(NO_TRACE_MAKE) cleanup
|
||||
|
|
|
|||
110
docs/adding.tex
110
docs/adding.tex
|
|
@ -478,3 +478,113 @@ module_exit(device_mtd_cleanup);
|
|||
MODULE_LICENSE("GPL");
|
||||
MODULE_AUTHOR("Me, myself and I <memyselfandi@domain.tld");
|
||||
\end{verbatim}
|
||||
|
||||
\subsection{Adding your target in OpenWrt}
|
||||
|
||||
Once you spotted the key changes that were made to the Linux kernel
|
||||
to support your target, you will want to create a target in OpenWrt
|
||||
for your hardware. This can be useful to benefit from the toolchain
|
||||
that OpenWrt builds as well as the resulting user-space and kernel
|
||||
configuration options.
|
||||
|
||||
Provided that your target is already known to OpenWrt, it will be
|
||||
as simple as creating a \texttt{target/linux/board} directory
|
||||
where you will be creating the following directories and files.
|
||||
|
||||
Here for example, is a \texttt{target/linux/board/Makefile}:
|
||||
|
||||
\begin{Verbatim}[frame=single,numbers=left]
|
||||
#
|
||||
# Copyright (C) 2009 OpenWrt.org
|
||||
#
|
||||
# This is free software, licensed under the GNU General Public License v2.
|
||||
# See /LICENSE for more information.
|
||||
#
|
||||
include $(TOPDIR)/rules.mk
|
||||
|
||||
ARCH:=mips
|
||||
BOARD:=board
|
||||
BOARDNAME:=Eval board
|
||||
FEATURES:=squashfs jffs2 pci usb
|
||||
|
||||
LINUX_VERSION:=2.6.27.10
|
||||
|
||||
include $(INCLUDE_DIR)/target.mk
|
||||
|
||||
DEFAULT_PACKAGES += hostapd-mini
|
||||
|
||||
define Target/Description
|
||||
Build firmware images for Evaluation board
|
||||
endef
|
||||
|
||||
$(eval $(call BuildTarget))
|
||||
\end{Verbatim}
|
||||
|
||||
\begin{itemize}
|
||||
\item \texttt{ARCH} \\
|
||||
The name of the architecture known by Linux and uClibc
|
||||
\item \texttt{BOARD} \\
|
||||
The name of your board that will be used as a package and build directory identifier
|
||||
\item \texttt{BOARDNAME} \\
|
||||
Expanded name that will appear in menuconfig
|
||||
\item \texttt{FEATURES} \\
|
||||
Set of features to build filesystem images, USB, PCI, VIDEO kernel support
|
||||
\item \texttt{LINUX\_VERSION} \\
|
||||
Linux kernel version to use for this target
|
||||
\item \texttt{DEFAULT\_PACKAGES} \\
|
||||
Set of packages to be built by default
|
||||
\end{itemize}
|
||||
|
||||
A partial kernel configuration which is either named \texttt{config-default} or which matches the kernel version \texttt{config-2.6.x} should be present in \texttt{target/linux/board/}.
|
||||
This kernel configuration will only contain the relevant symbols to support your target and can be changed using \texttt{make kernel\_menuconfig}.
|
||||
|
||||
To patch the kernel sources with the patches required to support your hardware, you will have to drop them in \texttt{patches} or in \texttt{patches-2.6.x} if there are specific
|
||||
changes between kernel versions. Additionnaly, if you want to avoid creating a patch that will create files, you can put those files into \texttt{files} or \texttt{files-2.6.x}
|
||||
with the same directory structure that the kernel uses (e.g: drivers/mtd/maps, arch/mips ..).
|
||||
|
||||
The build system will require you to create a \texttt{target/linux/board/image/Makefile}:
|
||||
|
||||
\begin{Verbatim}[frame=single,numbers=left]
|
||||
#
|
||||
# Copyright (C) 2009 OpenWrt.org
|
||||
#
|
||||
# This is free software, licensed under the GNU General Public License v2.
|
||||
# See /LICENSE for more information.
|
||||
#
|
||||
include $(TOPDIR)/rules.mk
|
||||
include $(INCLUDE_DIR)/image.mk
|
||||
|
||||
define Image/BuildKernel
|
||||
cp $(KDIR)/vmlinux.elf $(BIN_DIR)/openwrt-$(BOARD)-vmlinux.elf
|
||||
gzip -9 -c $(KDIR)/vmlinux > $(KDIR)/vmlinux.bin.gz
|
||||
$(STAGING_DIR_HOST)/bin/lzma e $(KDIR)/vmlinux $(KDIR)/vmlinux.bin.l7
|
||||
dd if=$(KDIR)/vmlinux.bin.l7 of=$(BIN_DIR)/openwrt-$(BOARD)-vmlinux.lzma bs=65536 conv=sync
|
||||
dd if=$(KDIR)/vmlinux.bin.gz of=$(BIN_DIR)/openwrt-$(BOARD)-vmlinux.gz bs=65536 conv=sync
|
||||
endef
|
||||
|
||||
define Image/Build/squashfs
|
||||
$(call prepare_generic_squashfs,$(KDIR)/root.squashfs)
|
||||
endef
|
||||
|
||||
define Image/Build
|
||||
$(call Image/Build/$(1))
|
||||
dd if=$(KDIR)/root.$(1) of=$(BIN_DIR)/openwrt-$(BOARD)-root.$(1) bs=128k conv=sync
|
||||
|
||||
-$(STAGING_DIR_HOST)/bin/mkfwimage \
|
||||
-B XS2 -v XS2.ar2316.OpenWrt \
|
||||
-k $(BIN_DIR)/openwrt-$(BOARD)-vmlinux.lzma \
|
||||
-r $(BIN_DIR)/openwrt-$(BOARD)-root.$(1) \
|
||||
-o $(BIN_DIR)/openwrt-$(BOARD)-ubnt2-$(1).bin
|
||||
endef
|
||||
|
||||
$(eval $(call BuildImage))
|
||||
|
||||
\end{Verbatim}
|
||||
|
||||
\begin{itemize}
|
||||
\item \texttt{Image/BuildKernel} \\
|
||||
This template defines changes to be made to the ELF kernel file
|
||||
\item \texttt{Image/Build} \\
|
||||
This template defines the final changes to apply to the rootfs and kernel, either combined or separated
|
||||
firmware creation tools can be called here as well.
|
||||
\end{itemize}
|
||||
|
|
|
|||
|
|
@ -0,0 +1,61 @@
|
|||
Debugging hardware can be tricky especially when doing kernel and drivers
|
||||
development. It might become handy for you to add serial console to your
|
||||
device as well as using JTAG to debug your code.
|
||||
|
||||
\subsection{Adding a serial port}
|
||||
|
||||
Most routers come with an UART integrated into the System-on-chip
|
||||
and its pins are routed on the Printed Circuit Board to allow
|
||||
debugging, firmware replacement or serial device connection (like
|
||||
modems).
|
||||
|
||||
Finding an UART on a router is fairly easy since it only needs at
|
||||
least 4 signals (without modem signaling) to work : VCC, GND, TX and
|
||||
RX. Since your router is very likely to have its I/O pins working at
|
||||
3.3V (TTL level), you will need a level shifter such as a Maxim MAX232
|
||||
to change the level from 3.3V to your computer level which is usually
|
||||
at 12V.
|
||||
|
||||
To find out the serial console pins on the PCB, you will be looking
|
||||
for a populated or unpopulated 4-pin header, which can be far from
|
||||
the SoC (signals are relatively slow) and usually with tracks on
|
||||
the top or bottom layer of the PCB, and connected to the TX and RX.
|
||||
|
||||
Once found, you can easily check where is GND, which is connected to
|
||||
the same ground layer than the power connector. VCC should be fixed
|
||||
at 3.3V and connected to the supply layer, TX is also at 3.3V level
|
||||
but using a multimeter as an ohm-meter and showing an infinite
|
||||
value between TX and VCC pins will tell you about them being different
|
||||
signals (or not). RX and GND are by default at 0V, so using the same
|
||||
technique you can determine the remaining pins like this.
|
||||
|
||||
If you do not have a multimeter a simple trick that usually works is
|
||||
using a speaker or a LED to determine the 3.3V signals. Additionnaly
|
||||
most PCB designer will draw a square pad to indicate ping number 1.
|
||||
|
||||
Once found, just interface your level shifter with the device and the
|
||||
serial port on the PC on the other side. Most common baudrates for the
|
||||
off-the-shelf devices are 9600, 38400 and 115200 with 8-bits data, no
|
||||
parity, 1-bit stop.
|
||||
|
||||
\subsection{JTAG}
|
||||
|
||||
JTAG stands for Joint Test Action Group, which is an IEEE workgroup
|
||||
defining an electrical interface for integrated circuit testing and
|
||||
programming.
|
||||
|
||||
There is usually a JTAG automate integrated into your System-on-Chip
|
||||
or CPU which allows an external software, controlling the JTAG adapter
|
||||
to make it perform commands like reads and writes at arbitray locations.
|
||||
Additionnaly it can be useful to recover your devices if you erased the
|
||||
bootloader resident on the flash.
|
||||
|
||||
Different CPUs have different automates behavior and reset sequence,
|
||||
most likely you will find ARM and MIPS CPUs, both having their standard
|
||||
to allow controlling the CPU behavior using JTAG.
|
||||
|
||||
Finding JTAG connector on a PCB can be a little easier than finding the
|
||||
UART since most vendors leave those headers unpopulated after production.
|
||||
JTAG connectors are usually 12, 14, or 20-pins headers with one side of
|
||||
the connector having some signals at 3.3V and the other side being
|
||||
connected to GND.
|
||||
|
|
@ -30,8 +30,7 @@
|
|||
\section{Adding platform support}
|
||||
\input{adding}
|
||||
\section{Debugging and debricking}
|
||||
\subsection{Adding a serial port}
|
||||
\subsection{JTAG}
|
||||
\input{debugging}
|
||||
\section{Reporting bugs}
|
||||
\subsection{Using the Trac ticket system}
|
||||
\input{bugs}
|
||||
|
|
|
|||
Loading…
Reference in New Issue