How to use semihosting with STM32CubeIDE and STM32
Summary
Semihosting can be used to enable code running on STM32 to communicate with the host computer during a debug session. This makes it possible to use host computer I/O (for example keyboard, display, or file system) instead of having such input/output resources on the embedded system during development.
1. Using semihosting with STM32CubeIDE
To use semihosting with STM32CubeIDE some updates are needed to be done in the project. A debugger supporting semihosting is also required. This article guides on how to enable semihosting when using OpenOCD, ST-LINK and STM32 devices.
Note1: ST-LINK GDB server does not support semihosting!
Note2: Please consult SEGGER documentation if semihosting with SEGGER J-LINK is preferred.
2. Update STM32CubeIDE project
2.1. Remove default syscalls.c
Remove default <syscalls.c> file from build if this file is included in STM32CubeIDE project.
2.2. Update main.c
Add the following two lines in beginning of main.c to include <stdio.h> and to use initialise_monitor_handles() prototype.
#include <stdio.h>
extern void initialise_monitor_handles(void);
Add a call to initialise_monitor_handles() function in the beginning of main() function and some variables to be used for semihosting.
int main(void)
{
/* USER CODE BEGIN 1 */
initialise_monitor_handles();
char s[50];
char *p;
FILE *fp;
p=s;
Add some semihosting commands into main() function. Example: Using scanf, printf, fopen, fclose, and fprintf.
/* Infinite loop */
/* USER CODE BEGIN WHILE */
printf("Hello, World!\n");
fp=fopen("c:\\dev\\mytest.txt", "w");
while (1)
{
printf("Enter string:\n");
scanf("%s", p);
printf("\nReceived string: ");
printf(p);
printf("\n");
fprintf(fp,p);
fprintf(fp,"\n");
fclose(fp);
HAL_Delay(500);
fp=fopen("c:\\dev\\mytest.txt", "a");
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
2.3. Update GCC Linker configuration
In Libraries add “rdimon” library.
In Miscellaneous add Other flags “-specs=rdimon.specs”
2.4. Build
The project is now updated to use semihosting. Build the project.
3. Debug with semihosting
3.1. Create/Update OpenOCD debug configuration
Create a new debug configuration for the project or update an existing one. Make sure that OpenOCD is used.
Note: ST-LINK GDB server does not support semihosting.
Add “monitor arm semihosting enable” initialization command in Debug Configurations - Startup tab.
3.2. Debug
The Debug Console view is used for semihosting input/output and when debugging it will ask to enter strings…
Example: Entering “TEST” and “123456”
Open On-Chip Debugger 0.10.0+dev-01288-g7491fb4 (2020-10-27-17:36) Licensed under GNU GPL v2 For bug reports, read http://openocd.org/doc/doxygen/bugs.html Info : Listening on port 6666 for tcl connections Info : Listening on port 4444 for telnet connections Info : STLINK V2J37M26 (API v2) VID:PID 0483:374B Info : Target voltage: 3.244649 .. .. semihosting is enabled target halted due to debug-request, current mode: Thread xPSR: 0x01000000 pc: 0x08000860 msp: 0x20018000, semihosting configuring PLL Info : Unable to match requested speed 8000 kHz, using 4000 kHz Info : Unable to match requested speed 8000 kHz, using 4000 kHz Info : Padding image section 0 at 0x08000194 with 12 bytes target halted due to debug-request, current mode: Thread xPSR: 0x01000000 pc: 0x08000a04 msp: 0x20018000, semihosting Hello, World! Enter string: TEST Received string: TEST Enter string: 123456 Received string: 123456 Enter string:
Stop the debug session to analyze the log file.
4. Analyze debug session
The program opens and writes to the file c:\dev\mytest.txt. Open the <mytest.txt> file and information from the debug session can be seen.