Maple JTAG How To
This is a page about using JTAG with Maple - JTAG will allow you to use a debugger program like GDB to debug programs running on the Maple. You can also use the JTAG adapter to re-flash (re-install) the bootloader in case you "brick" the board and can't install programs on it via the bootloader.
Contents
JTAG Debugger
You need a piece of hardware called a JTAG debugger to manage the connection and debugging of the Maple. These plug into your computer via USB and into the Maple via its JTAG port.
- Olimex ARM-USB-OCD - only this debugger is known to work. Olimex's ARM-USB-TINY is known not to work.
- ARM-USB-OCD at Sparkfun
If you know of other JTAG debuggers that are known to work, add them here.
JTAG Adapter
Maple's 8-pin JTAG port is non-standard, so you need an adapter circuit to go between the ARM 20-pin connector and the Maple 8-pin connector.
- Maple JTAG adapter circuit and board layout - the one in Maple's source tree works, but has unneeded resistors. This circuit is also known to work.
- Circuit diagram
- picture of PCB design
OpenOCD
OpenOCD is a program that can talk with the JTAG debugger. You can give commands to it directly, or you can configure GDB to use it to control your Maple board.
Download the latest version of OpenOCD, build it, and install it. Then you can use Maple's build tools (Make) to run the JTAG debugger, or run it standalone so you can connect via another program.
You will need to edit the OpenOCD configuration files to make them work with recent OpenOCD versions. Make the following changes:
- File support/openocd/run.cfg:
- Add at the beginning of the file
#daemon configuration telnet_port 4444 gdb_port 3333
Replace this line:
flash bank stm32x 0x08000000 0x00020000 0 0 $_TARGETNAME
- with this:
set _FLASHNAME $_CHIPNAME.flash flash bank $_FLASHNAME stm32x 0x08000000 0x00020000 0 0 $_TARGETNAME
Eclipse C/C++
If you want to use a visual debugger instead of GDB, you can use the Eclipse C/C++ tools. Here is an outline of the steps:
- OpenOCD 0.4.0 from source.
- Install the Codesourcery ARM toolchain from http://static.leaflabs.com/pub/codesourcery/ The direct URL for linux is: http://static.leaflabs.com/pub/codesourcery/arm-2009q3-68-arm-none-eabi-toolchain-linux32.tar.gz
- Install Eclipse C/C++ Helios from http://www.eclipse.org/downloads/
- Install the Zylin remote debugger Eclipse plugin using the instructions at http://opensource.zylin.com/embeddedcdt.html
- Configure OpenOCD and Zylin using this guide: http://linuxfreak.pl/elektronika/debugging-stm32-cortex-m3-microcontroller-using-eclipse-on-slackware
- Then I used Eclipse to launch OpenOCD, and started the debugger using a Debug Configuration. You can copy examples/blinky.cpp to main.cpp, then start and stop the program using the debugger!
Here is a screenshot of blinky.cpp (main.cpp) stopped at a breakpoint: http://imgur.com/9CZ6q
The USB interrupts are enabled, so single-stepping lands you in the USB interrupt service routine (ISR). You can disable the USB interrupts by commenting out the setupUSB() line in wirish/wirish.c .
Reflashing the bootloader
You can use OpenOCD to re-flash (re-install) the bootloader if you accidentally "brick" the board somehow - if you can't install programs via the bootloader any more and resetting doesn't help. Here's how.
- Read the guide here for background info: http://fun-tech.se/stm32/OpenOCD/gdb.php
- Build the Maple bootloader
- Check out a copy of the maple-bootloader from github: https://github.com/leaflabs/maple-bootloader
- Build it by typing 'make' in the root of the project
- Start OpenOCD:
$ openocd -f support/openocd/run.cfg Open On-Chip Debugger 0.4.0 (2010-11-28-20:19) Licensed under GNU GPL v2 For bug reports, read http://openocd.berlios.de/doc/doxygen/bugs.html 1000 kHz jtag_nsrst_delay: 100 jtag_ntrst_delay: 100 trst_and_srst separate srst_gates_jtag trst_push_pull srst_open_drain Info : clock speed 1000 kHz Info : JTAG tap: stm32.cpu tap/device found: 0x3ba00477 (mfg: 0x23b, part: 0xba00, ver: 0x3) Info : JTAG tap: stm32.bs tap/device found: 0x16410041 (mfg: 0x020, part: 0x6410, ver: 0x1) Info : stm32.cpu: hardware has 6 breakpoints, 4 watchpoints Info : JTAG tap: stm32.cpu tap/device found: 0x3ba00477 (mfg: 0x23b, part: 0xba00, ver: 0x3) Info : JTAG tap: stm32.bs tap/device found: 0x16410041 (mfg: 0x020, part: 0x6410, ver: 0x1)
- From another terminal window, telnet to the OpenOCD shell:
telnet localhost 4444
You should see something like:
Connected to localhost. Escape character is '^]'. Open On-Chip Debugger >
- Type the following into the OpenOCD shell:
reset halt flash probe 0 stm32x mass_erase 0 flash write_bank 0 build/maple_boot.bin 0 reset
- Disconnect the JTAG connector from the Maple board.
- Now you should be able to reset the board using the reset switch, the LED should blink rapidly, and you should be able to use the bootloader again.
Reset Halt
'reset halt' is an OpenOCD command that resets the board and then immediately halts it, leaving the debugger in control of the board before it starts executing code.
You cannot do a 'reset halt' command with OpenOCD using Maple revisions up to Maple rev 5, because nJTRST and nTRST are currently connected. They may be separated on future Maple revisions, and then a 'reset halt' would work.
