reading I/O register values with command line GDB

[M. Jeong]

Posted on December 18, 2017 at 16:54

Recently I found that STM32CubeMX support Makefile as well as SW4STM32. So far I worked with only the SW4STM32, but now I'm happy to move to the command line development with GCC, GNU make , stlink, and GDB. After spending time fixing minor bugs I could compile a blinky code and flashed my STM32L476 without problem. The blinky program is working as expected. 

Now I'm trying to debug the program with GDB. I ran st-util and arm-none-eabi-gdb using my .elf file. Then setting breakpoints and reading the values of variables were successful. But I wonder how to read I/O register values. On the System Workbench for STM32 it's very easy to check the state of the I/O registers. Would it be possible for one to do the same thing on the command line? For example, how can you read the values of GPIOB_MODER, GPIOB_OTYPER, and GPIOB_ODR registers at once?

[waclawek.jan]

Posted on December 18, 2017 at 17:02

Use -g3 when compiling, the compiler then adds macros into debug info.

Then in gdb simply type p /x *GPIOB

Enjoy! ;)

JW

[M. Jeong]

Posted on December 18, 2017 at 17:13

Hi JW,

thank you for the quick answer! The flag '-g3' worked. This is awesome.. I feel like I don't need the heavy IDE anymore.

I have two questions. Is there a command which displays the register values in binary format? Would it be bad that one uses the -g3 option to compile a release version(for flashing)?

thanks

[waclawek.jan]

Posted on December 18, 2017 at 17:23

Is there a command which displays the register values in binary format?

Use /t modifier instead of /x in p (print) command. The result is IMO less readable than hexadecimal.

Compare

(gdb) p /t TIM3->CCMR1

$39 = 1111000111110001

(gdb) p /x TIM3->CCMR1

$40 = 0xf1f1

Would it be bad that one uses the -g3 option to compile a release version(for flashing)?

Shouldn't matter, as -g3 should influence only the debug information, which does not go to the binary for FLASH.

JW