Posted on June 25, 2012 at 06:08I'm trying to learn how to use the basic timers, without the benefit of a library, so I have been reading the RM0090 reference manual. As a simple test I want to toggle the blue LED on the dev board (pin D15) once per second.
I wrote the code below, but the LED does not come on. The weird thing is when I run a debugger and setup a brakepoint to print out some information, it actually works. If I remove the brake point it stops working. Any ideas?
Code:
============================================
#include ''stm32f4xx.h''
#include ''core_cm4.h''
unsigned long i = 0;
int main() {
RCC->AHB1ENR |= RCC_AHB1ENR_GPIODEN; // Enable GPIOD clock
GPIOD->MODER |= GPIO_MODER_MODER15_0; // Enable output mode for D15
RCC->APB1ENR |= RCC_APB1ENR_TIM6EN; // Enable TIM6 clock
NVIC_EnableIRQ(TIM6_DAC_IRQn); // Enable TIM6 IRQ
TIM6->DIER |= TIM_DIER_UIE; // Enable interrupt on update event
TIM6->PSC = 41999; // Set prescaler to 41999
TIM6->ARR = 999; // Set auto-reload to 999
TIM6->CR1 |= TIM_CR1_CEN; // Enable TIM6 counter
while(1) {
// do nothing
}
}
void TIM6_DAC_IRQHandler() {
i++;
GPIOD->ODR ^= (1 << 15); // Toggle D15
TIM6->SR = 0; // Interrupt has been handled
}
============================================
Debugger setup:
============================================
$ arm-none-eabi-gdb -silent -ex 'target extended-remote localhost:4242' firmware.elf
Reading symbols from /stm32f4/projects/LED Blinking with TIM6/firmware.elf...done.
Remote debugging using localhost:4242
Reset_Handler () at startup_stm32f4xx.s:69
69 movs r1, #0
(gdb) break TIM6_DAC_IRQHandler
Breakpoint 1 at 0x8000188: file main.c, line 23.
(gdb) commands
Type commands for breakpoint(s) 1, one per line.
End with a line saying just ''end''.
>print i
>print *(unsigned long*) 0x40020c14
>continue
>end
(gdb) run
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /stm32f4/projects/LED Blinking with TIM6/firmware.elf
Note: automatically using hardware breakpoints for read-only addresses.
TIM6_DAC_IRQHandler () at main.c:23
23 i++;
(gdb) c
Continuing.
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$1 = 1
$2 = 32768
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$3 = 2
$4 = 0
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$5 = 3
$6 = 32768
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$7 = 4
$8 = 0
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$9 = 5
$10 = 32768
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$11 = 6
$12 = 0
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$13 = 7
$14 = 32768
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$15 = 8
$16 = 0
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$17 = 9
$18 = 32768
Breakpoint 1, TIM6_DAC_IRQHandler () at main.c:23
23 i++;
$19 = 10
$20 = 0
^CBreakpoint 1, Quit
(gdb)
============================================
-Farrell
