Enable ITM printf output using openocd/gdb on STM32H7

[cdmeister]

Hello,

I am looking up on how to capture printf output using ITM on my stm32H723ZG board. Most tutorials I see online are using some sort of IDE. I tried using CubeMX and it works there but I would like to use gdb/openocd since that is my preferred way of debugging.

I am wondering how is it possible to enable printf output using gdb/openocd combo? What setup needs to be done on the gdb side and on the openocd side?

Code wise, I know I have to implement the _write function which I have done below for GCC.

int _write(int fd, char *ptr, int len){                                            
  size_t i;                                                                     
  for(i=0; i<len;i++){                                                             
    ITM_SendChar(ptr[i]);                                                          
  }                                                                             
  return len;                                                                   
}                                                                                  
    

Also i added in the --specs=nosys.specs flag in my makefile

Do i need to setup some ITM hardware as well? Part of the confusion for me is that when i used CubeMx it doesn't seem to generate any additional ITM setup code so I not sure if I need to do.

Here is what I have for my gdbscript:

target extended-remote localhost:3333                                           
file build/bare_metal.elf                                                          
load                                                                               
display /x $r0                                                                     
display /x $r1                                                                     
display /x $r2                                                                     
display /x $r3                                                                     
display /x $r4                                                                     
display /x $msp                                                                    
display /x $psp                                                                    
display /x $control                                                                
display /x $lr                                                                     
display /x $xPSR                                                                   
                                                                                   
monitor tpiu config internal itm.txt uart off 64000000 106667                      
monitor itm port 0 on     

Here is my openocd:

# This is an NUCLEO-H723ZG board with a single STM32H723ZGTx chip               
#                                                                                  
# Take care that such file, as generated, may be overridden without any early notice. Please have a look to debug launch configuration setup(s)
# https://github.com/zephyrproject-rtos/zephyr/issues/51508                        
# https://github.com/zephyrproject-rtos/zephyr/issues/50590                        
                                                                                   
source [find interface/stlink-dap.cfg]                                             
transport select dapdirect_swd                                                     
                                                                                   
                                                                                   
set WORKAREASIZE 0x8000                                                            
                                                                                   
                                                                                   
set CHIPNAME STM32H723ZGTx                                                         
set BOARDNAME NUCLEO-H723ZG                                                        
                                                                                   
source [find target/stm32h7x.cfg]                                               
                                                                                
# Enable debug when in low power modes                                          
set ENABLE_LOW_POWER 1                                                          
                                                                                
# Stop Watchdog counters when halt                                              
set STOP_WATCHDOG 1                                                             
                                                                                
# STlink Debug clock frequency                                                  
set CLOCK_FREQ 8000                                                             
                                                                                
# Reset configuration                                                           
# use hardware reset, connect under reset                                       
# connect_assert_srst needed if low power mode application running (WFI...)     
reset_config srst_only srst_nogate connect_assert_srst                          
set CONNECT_UNDER_RESET 1                                                       
set CORE_RESET 0                                                                
                                                                                
# ACCESS PORT NUMBER                                                            
set AP_NUM 0                                                                    
# GDB PORT                                                                      
set GDB_PORT 3333                                                               
# Due to the use of connect_assert_srst, running gdb requires                   
# to reset halt just after openocd init.                                        
rename init old_init                                                            
proc init {} {                                                                  
       old_init                                                                 
       reset halt                                                               
}                                                                               
~