Semihosting

Semihosting is a mechanism for ARM targets to communicate input/output requests from application code to a host computer running a debugger. This mechanism can be used, for example, to enable functions in the C library, such as printf() and scanf(), to use the screen and keyboard of the host rather than having a screen and keyboard on the target system.

Guide Semihosting for IAR

NOTE: After the setting both "printf" and "scanf" are available for debugging.

Step 1: Setting up the environment

1. To set debugger options, choose Project>Options. In the Debugger category, click the Setup tab.
2. Select Run to main and click OK. This ensures that the debug session starts by running the main function.
3. The project is now ready to be built.

Step 2: Building the project

1. Compile and link the project by choosing Project>Make or F7.
2. Alternatively, click the Make button on the tool bar. The Make command compiles and links those files that have been modified.

Step 3: Starting semihosting

1. Choose "Semihosting_IAR" project -> "Options" -> "Debugger" -> "J-Link/J-Trace".
2. Choose tab "J-Link/J-Trace" -> "Connection" tab -> "SWD".
3. Start the project by choosing Project>Download and Debug.
4. Choose View>Terminal I/O to display the output from the I/O operations.

Guide Semihosting for Keil µVision

NOTE: Keil supports Semihosting only for Cortex-M3/Cortex-M4 cores.

Step 1: Prepare code

Remove function fputc and fgetc is used to support KEIL in "fsl_debug_console.c" and add the following code to project.

#pragma import(__use_no_semihosting_swi)

volatile int ITM_RxBuffer = ITM_RXBUFFER_EMPTY;       /* used for Debug Input */
struct __FILE
{
    int handle;
};
FILE __stdout;
FILE __stdin;

int fputc(int ch, FILE *f)
{
    return (ITM_SendChar(ch));
}

int fgetc(FILE *f)
{ /* blocking */
    while (ITM_CheckChar() != 1)
        ;
    return (ITM_ReceiveChar());
}

int ferror(FILE *f)
{
    /* Your implementation of ferror */
    return EOF;
}

void _ttywrch(int ch)
{
    ITM_SendChar(ch);
}

void _sys_exit(int return_code)
{
label:
    goto label; /* endless loop */
}

Step 2: Setting up the environment

1. In menu bar, choose Project>Options for target or using Alt+F7 or click.
2. Select "Target" tab and not select "Use MicroLIB".
3. Select “Debug” tab, select “J-Link/J-Trace Cortex” and click “Setting button”.
4. Select “Debug” tab and choose Port:SW, then select "Trace" tab, choose "Enable" and click OK.

Step 3: Building the project

1. Compile and link the project by choosing Project>Build Target or using F7.

Step 4: Building the project

1. Choose “Debug” on menu bar or Ctrl F5.
2. In menu bar, choose "Serial Window" and click to "Debug (printf) Viewer".
3. Run line by line to see result in Console Window.

Guide Semihosting for KDS

NOTE: After the setting use "printf" for debugging.

Step 1: Setting up the environment

1. In menu bar, choose Project>Properties>C/C++ Build>Settings>Tool Settings.
2. Select “Libraries” on “Cross ARM C Linker” and delete “nosys”.
3. Select “Miscellaneous” on "Cross ARM C Linker”, add “-specs=rdimon.specs” to “Other link flages” and tick “Use newlib-nano”, and click OK.

Step 2: Building the project

1. In menu bar, choose Project>Build Project.

Step 3: Starting semihosting

1. In Debug configurations, choose "Startup" tab, tick “Enable semihosting and Telnet”. Press “Apply” and “Debug”.
2. After clicking Debug, the Window is displayed same as below. Run line by line to see the result in the Console Window.

Guide Semihosting for MCUX

Step 1: Setting up the environment

1. To set debugger options, choose Project>Properties. select the setting category.
2. Select Tool Settings, unfold MCU C Compile.
3. Select Preprocessor item.
4. Set SDK_DEBUGCONSOLE=0, if set SDK_DEBUGCONSOLE=1, the log will be redirect to the UART.

Step 2: Building the project

1. Compile and link the project.

Step 3: Starting semihosting

1. Download and debug the project.
2. When the project runs successfully, the result can be seen in the Console window.

Semihosting can also be selected through the "Quick settings" menu in the left bottom window, Quick settings->SDK Debug Console->Semihost console.

Guide Semihosting for ARMGCC

Step 1: Setting up the environment

1. Turn on "J-LINK GDB Server" -> Select suitable "Target device" -> "OK".
2. Turn on "PuTTY". Set up as follows.
   • "Host Name (or IP address)" : localhost
   • "Port" :2333
   • "Connection type" : Telet.
   • Click "Open".
3. Increase "Heap/Stack" for GCC to 0x2000:

Add to "CMakeLists.txt"

SET(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} --defsym=__stack_size__=0x2000")

SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} --defsym=__stack_size__=0x2000")

SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} --defsym=__heap_size__=0x2000")

SET(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} --defsym=__heap_size__=0x2000")

Step 2: Building the project

1. Change "CMakeLists.txt":

   Change "SET(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} –specs=nano.specs")"

   to "SET(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} –specs=rdimon.specs")"

   Replace paragraph

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -fno-common")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -ffunction-sections")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -fdata-sections")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -ffreestanding")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -fno-builtin")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -mthumb")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -mapcs")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -Xlinker")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} --gc-sections")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -Xlinker")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -static")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -Xlinker")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -z")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -Xlinker")

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} muldefs")

   To

   SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} --specs=rdimon.specs ")

   Remove

   target_link_libraries(semihosting_ARMGCC.elf debug nosys)

2. Run "build_debug.bat" to build project

   Step 3: Starting semihosting

   1. Download the image and set as follows. cd D:-sdk-2.0-origin d: C:~2~1\4BD65~1.920\bin\arm-none-eabi-gdb.exe target remote localhost:2331 monitor reset monitor semihosting enable monitor semihosting thumbSWI 0xAB monitor semihosting IOClient 1 monitor flash device = MK64FN1M0xxx12 load semihosting_ARMGCC.elf monitor reg pc = (0x00000004) monitor reg sp = (0x00000000) continue
   2. After the setting, press "enter". The PuTTY window now shows the printf() output.