Eclipse with GDB is great: it comes with a graphical front end for debugging. But sometimes it is all about to download a program. Is it really necessary to launch an IDE like Eclipse to program or quickly debug a board? With the GNU Debugger (GDB), the answer is ‘no’: GDB comes with a command line debugger which is designed exactly for this: providing a command line interface for programming/downloading and debugging, bypassing any GUI (Graphical User Interface).
In “OpenOCD/CMSIS-DAP Debugging with Eclipse and without an IDE” I have documented how this works with the combination of GDB+OpenOCD+CMSIS-DAP, but this works in a similar way with Segger J-Link and P&E Multilink, as both come with a GDB server implementation too (e.g. if I use the Freescale Kinetis Design Studio or a DIY Eclipse IDE).
What I need is:
- The GDB client: this comes with the GNU tools, e.g. the GNU ARM Embedded (launchpad).
- The GDB server (e.g. from P&E or Segger). Both come installed with the Kinetis Design Studio.
- And a board :-). I use here the FRDM-KL25Z board as it works with P&E, Segger, and OpenOCD/CMSIS-DAP GDB servers.
GDB Debugging Chain
To debug with GDB, I need a client, a server, a probe and of course a board:
The client is the gdb executable (arm-none-eabi-gdb.exe) on the host. It talks over a TCP/IP connection/port to the GDB server. The server is usually an executable running on the same machine, but it can run anywhere in the network too on a remote machine. Popular GDB servers are available from Segger, P&E or as well as open source (e.g. OpenOCD, see “OpenOCD/CMSIS-DAP Debugging with Eclipse and without an IDE“). Kinetis Design Studio v2.0.0 comes with all these three servers. The server needs to talk to the microcontroller/device/board using a JTAG/SWD connection: this can be a probe from vendors like Segger (J-Link, for example), P&E (USB Multilink, for example) or with CMSIS-DAP (e.g. on the FRDM-KL25Z board, see https:\\www.freescale.com\opensda). Both Segger and P&E provide firmware files for the FRDM boards to behave like a hardware probe, see “Segger J-Link Firmware for OpenSDAv2” and “New P&E OpenSDA Firmware v114“.
The GDB client for ARM is named arm-none-eabi-gdb.exe, and in the case of KDS V2.0.0 it is located inside the toolchain\bin folder:
start the GDB client with
The GDB client can be used with many GDB servers. The Segger and P&E specifics will be handled after this section.
P&E GDB Server
There is a GDB server from P&E available from http://www.pemicro.com/products/product_viewDetails.cfm?product_id=15320151. Alternatively, a P&E GDB server is included in the Freescale Kinetis Design Studio (KDS) (https://www.freescale.com/kds).
In case of KDS V2.0.0, the P&E GDB server is inside the eclipse\plugins\com.pemicro.debug.gdbjtag.pne folder. The folder name depends on the version, and there is a sub folder depending on Windows or Linux (win32 on Windows). The GDB server is named ‘pegdbserver_console.exe’:
The most important command line arguments are:
- -startserver: starts the server
- -device: specifies the device
- -devicelist: lists the supported devices
These and other command line options are documented in
To find out the list of supported devices, use the -devicelist command:
💡 the real path to the P&E gdb server depends on your version installed. I’m using KDS v2.0.0
I start the server for the device on the FRDM-KL25Z on a cmd/DOS prompt with
pegdbserver_console.exe -startserver -device=KL25Z128M4
and it will report something like this:
P&E GDB Server, Version 5.13.02.00 Copyright 2014, P&E Microcomputer Systems Inc, All rights reserved Loading library C:\Freescale\KDS_2.0.0\eclipse\plugins\com.pemicro.debug.gdbjtag .pne_126.96.36.199411191655\win32\gdi\unit_ngs_arm_internal.dll ... Done. Command line arguments: -startserver -device=KL25Z128M4 Device selected is kl25z128m4 PE-ERROR: Unable to auto-detect debug hardware. Please specify on the command-line. Halting. C:\Freescale\KDS_2.0.0>eclipse\plugins\com.pemicro.debug.gdbjtag.pne_188.8.131.5241 1191655\win32\pegdbserver_console.exe -startserver -device=KL25Z128M4 P&E GDB Server, Version 5.13.02.00 Copyright 2014, P&E Microcomputer Systems Inc, All rights reserved Loading library C:\Freescale\KDS_2.0.0\eclipse\plugins\com.pemicro.debug.gdbjtag .pne_184.108.40.206411191655\win32\gdi\unit_ngs_arm_internal.dll ... Done. Command line arguments: -startserver -device=KL25Z128M4 Device selected is kl25z128m4 HW Auto-Selected : Interface=OPENSDA Port=DBA07E44 ; USB1 : OpenSDA (DBA07E44) Connecting to target. OpenSDA detected - Flash Version 1.14 Device is KL25Z128M4. Mode is In-Circuit Debug. 'Kinetis' is a registered trademark of Freescale. (C)opyright 2012, P&E Microcomputer Systems, Inc. (www.pemicro.com) API version is 101 Server running on 127.0.0.1:7224
With this the server is running and waiting on port 7224 for a connection from the GDB client.
To connect to the P&E GDB server, use this in the gdb client:
target remote localhost:7224
Some monitor commands are documented here: http://www.pemicro.com/forums/forum.cfm?forum_topic_id=3990
💡 I have not found a formal document (yet?) about the P&E monitor commands supported. A tip is to look in the Eclipse debug console view for hints 🙂
_reset ; Reset the MCU _r0 ... _r15 ; Change CPU register Value (param : longvalue) _fill.w ;Fill memory words (params : startaddr endaddr wordvalue) _fill.l ;Fill memory longwords (params : startaddr endaddr longwordvalue) _pc ;Set program counter (param: longvalue)
So to reset the microcontroller, use
Then I can use the load and file commands to load my application for debug:
Below is the log of a debug session with P&E GDB Server using the ARM GDB client:
Segger GDB Server
There is a GDB server from Segger available from https://www.segger.com/jlink-gdb-server.html. Alternatively, a Segger GDB server is included in the Freescale Kinetis Design Studio (KDS) (https://www.freescale.com/kds). Segger has a GUI version (on Windows only, as far as I know) and a console/command line version. I’m using the command line version here.
The Segger GDB server is named JLinkGDBServerCL.exe and located in the C:\Freescale\KDS_2.0.0\segger folder.
Start it with
The Segger GDB server expects a connection on port 2331. In the GDB client, I use
target remote localhost:2331
I can reset the target from the GDB client.
💡 Documentation will commands can be found here: https://www.segger.com/admin/uploads/productDocs/UM08005_JLinkGDBServer.pdf
Next, I select the device to be used:
monitor device = MKL25Z128xxx4
Then I can use the load and file commands to load my application for debug:
Below is the log of a debug session with Segger GDB Server using the ARM GDB client:
GDB Client Commands to Load/Program the Device
The following commands in the gdb client are generic for both P&E and Segger.
Load the application code with the load command:
Use the file command to load debug symbols in gdb:
Use the continue command to start/continue execution:
With CTRL+C I can stop execution.
With the quit command I terminate the gdb session:
💡 There are plenty of tips and trick for GDB available, see as well http://haifux.org/lectures/222/GDB_haifux_David_Khosid.pdf. For example you can put default commands into a .gdbinit file. Have as well a look https://sourceware.org/gdb/current/onlinedocs/gdb/ for a list of gdb commands.
Now if it is about to flash/program a bunch of boards, it is much easier to do this from a script, batch or command file. For example I create a text file with the following content:
# Segger: listen on port target remote localhost:2331 # Segger: reset device monitor reset # Segger: specify flash of device monitor device = MKL25Z128xxx4 # load/flash application file load c:/tmp/KL25Z_green.elf # exit gdb quit
Now with the GDB server running, I can launch the gdb client with the -x option, passing that command file to it:
💡 GDB uses a similar file named .gdbinit (if it exists) to be executed at gdb startup. So that would be a good place for common settings.
arm-none-eabi-gdb.exe -x gdb_flash.txt
That way it will flash my binary file to the board:
Be free to write your own script: that way you can add the download to your make file or anything else which uses a command line interface.
GDB comes with a nice command line interface, so no GUI or IDE is needed for debugging or just downloading/flashing an image to a device. The GNU tools come with a generic GDB client which needs to talk to a GDB server, which can be from P&E, Segger or something else like OpenOCD. The commands supported in the server differ from one GDB server to another. With little work, it is possible to setup a command line environment for programming and debugging which is very useful for automated testing or automation in general.
Happy Serving 🙂
- GDB commands: https://sourceware.org/gdb/current/onlinedocs/gdb/
- Segger GDB Server and Documentation: https://www.segger.com/jlink-gdb-server.html
- PE Micro GDB Server: http://www.pemicro.com/products/product_viewDetails.cfm?product_id=15320151
- Freescale Kinetis Design Studio download: https://www.freescale.com/kds
- Command line debugging with gdb: http://www.chemie.fu-berlin.de/chemnet/use/info/gdb/gdb_3.html and http://www.chemie.fu-berlin.de/chemnet/use/info/gdb/gdb_16.html#SEC143