Using a Raspberry Pi as a JTAG Dongle

Alden Hart edited this page Dec 18, 2013 · 5 revisions

##Compiling OpenOCD on the RaspberryPi:

You will need:

Note: I am using Occidentalis v0.2 from Adafruit. You should be able to install it fresh, follow the instructions to complete the setup, and then make sure ssh is turned on.

We are using a recent version of OpenOCD that has gpio-bitbang capabilities. This has been added since their latest release (v0.6.1 as I write this), and the openocd package that apt-get will give you is even older (v0.5.x). This means we have to compile it from the source, but don't worry. I've figured out the steps.

First, get the dependencies, and then grab the code:
NOTE: These commands are to be ran on the raspberry pi

sudo apt-get update
sudo apt-get install -y autoconf libtool libftdi-dev
git clone --recursive git:// openocd-git && cd openocd-git

This is the compile as one massive command, copy and paste it in, and let it run. It'll take a while.

./bootstrap &&\
./configure --enable-sysfsgpio\
     --enable-maintainer-mode \
     --disable-werror \
     --enable-ft2232_libftdi \
     --enable-ep93xx \
     --enable-at91rm9200 \
     --enable-usbprog \
     --enable-presto_libftdi \
     --enable-jlink \
     --enable-vsllink \
     --enable-rlink \
     --enable-arm-jtag-ew \
     --enable-dummy \
     --enable-buspirate \
     --enable-ulink \
     --enable-presto_libftdi \
     --enable-usb_blaster_libftdi \
} > openocd_build.log 2>&1

Note: You might get an error about not having makeinfo. It's not a problem.

Now, to actually install OpenOCD (You'll probably be asked for your password for any command that starts with sudo):

sudo make install
sudo cp -r tcl/ /usr/share/openocd
cd /usr/share/openocd/board
sudo wget

##Wiring it up:

TODO: Add images, cleanup description.

Using this schematic of the Arduino Due and this reference image of the Pi's GPIO pins, you'll connect these pins from the Due to the Pi (ideally with the power off -- you've been warned):

Due Pi
JTAG_TCK (Debug header) 11
JTAG_TMS (Debug header) 25
JTAG_TDI (JTAG header, with clip) 10
JTAG_TDO (JTAG header, with clip) 9
MASTER-RESET (Debug header, closest to the reset button) 7
GND (Debug header) GND

The JTAG header on the Due is the really small 5x2 pin header on the corner near the Reset button. Note that on the Due schematic, there's a small notched corner on the JTAG header symbol. That's matched by a dot on the silkscreen near a corner of the JTAG header of the actual Due. You'l use the clips to connect to two of those small pins.

The Debug header is the 0.1" male header right next to the JTAG header. You'll use F-F headers to connect to all four of those connections.

You'll also need to power the Due separately from the Pi, or you'll get random resets on the Pi.

##Running it:

Test that it connects properly:

sudo openocd -s /usr/share/openocd -f board/raspberrypi-due.tcl

You should get something that looks like this:

pi@raspberrypi:~$ sudo openocd -s /usr/share/openocd -f board/raspberrypi-due.tcl
Open On-Chip Debugger 0.7.0-dev-00217-g74db7f9 (2013-04-03-02:00)
Licensed under GNU GPL v2
For bug reports, read
Info : only one transport option; autoselect 'jtag'
SysfsGPIO nums: tck = 11, tms = 25, tdi = 10, tdi = 9
SysfsGPIO num: trst = 7
adapter speed: 500 kHz
adapter_nsrst_delay: 100
jtag_ntrst_delay: 100
cortex_m3 reset_config sysresetreq
Info : SysfsGPIO JTAG bitbang driver
Info : This adapter doesn't support configurable speed
1Info : JTAG tap: sam3.cpu tap/device found: 0x4ba00477 (mfg: 0x23b, part: 0xba00, ver: 0x4)
Info : sam3.cpu: hardware has 6 breakpoints, 4 watchpoints

Now, on you dekstop computer you can run gdb, but it has to be the arm gdb. I'm using Yatargo on OS X. You can also dig around in the Arduino distribution and find it.

Debugging an Arduino sketch

Maks sure you can program the Due from the Arduino environment normally.

Turn on "Show verbose output during: [X] Debugging" in the Arduino preferences, and then compile your sketch.

You should see a line similar (on OS X) to this one, near the end of the listing in the Arduino console (lines broken for readability):

/Applications/ -O binary

Copy the part that starts with / and ends with arm-none-eabi-objcopy and replace the objcopy with gdb to make the gdb command. (Add .exe and flip the slashes as needed for windows.) Paste that into a command line, and add a space.

Now, copy the part that starts with / and ends with .elf and paste it at the end of the gdb command.

You should get something like this (except you won't have [...] -- I put those there because the command get really long):

/Applications/[...]/bin/arm-none-eabi-gdb /var/[...]/DebugTest.cpp.elf
GNU gdb (GDB)
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "--host=i386-apple-darwin10.3.0 --target=arm-none-eabi".
For bug reporting instructions, please see:
Reading symbols from /private/var/[...]/DebugTest.cpp.elf...done.

Now, you need the IP or DNS address of the Pi. On my local network, it's address is raspberrypi -- replace that as you see it below as needed.

( SIDE NOTE: Making ssh keys are beyond the scope of this, but here's the command I used to send the keys to the Pi (whose) so that I won't have to enter my password anymore: cat ~/.ssh/ | ssh pi@raspberrypi -C "mkdir .ssh; cat - >> ~/.ssh/authorized_keys" )

Now, at the (gdb) prompt, enter target extended-remote raspberrypi:3333, and it should look like this:

(gdb) target extended-remote raspberrypi:3333
Remote debugging using raspberrypi:3333
0x00080170 in Reset_Handler ()

Now you have debugger control of the Due, from your computer, through the Pi.

A few commands

quit -- exits the debugger. (You'll still need to hit Ctrol-C on the Pi to stop the OpenOCD that's running) monitor reset halt -- restarts the Due and stops it before running run -- almost the same, starts he Due from reset-state (I believe this may not wipe RAM or registers properly) load -- upload the hex file. (Will also cause gdb to rescan it for changes.) You can recompile in the Arduino, and upload right over the debug connection. file <filename.elf> -- loads another .elf file into gdb. Use load to upload it. ^c -- type Control-C to stop the sketch running and drop into the debugger. break <function|filename:line> -- see the gdb command reference. Note: gdb doesn't know about the .ino file, and so it's difficult to see code that's in the sketch. This is a problem I'm yet to overcome properly. c -- short for continue. Resumes running after a break. s -- single-line step, over subroutines. n -- next line -- single line step into subroutines.

See the gdb quick reference for more commands. Google is your friend as well.

I was even able to run it with the Pi connected to the network via WiFi.

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