(switching to main email account)
Thanks Mike for your explanation, that explained the vector table. It
turned out that the culprit was the "Maple DFU Bootloader" I am using to
flash the code. I thought it was irrelevant, since I tried Frank's
suggestion already, so how could it mess things up, right?
Since I was unable to get the DFU code to work from Leaflabs Github (
https://github.com/leaflabs/maple-bootloader) I've used a binary (
http://static.leaflabs.com/pub/leaflabs/maple-bootloader/maple_mini_boot.bin).
As I do not know for sure from which source the binary was compiled, I am
guessing that the bootloader lacks the setup of SCB_VTOR and just jumps to
0x8005000.
Lesson learned: use SWD instead of buggy bootloaders.
Best,
Jorik
On 23 February 2015 at 15:33, Jorik Jonker <[email protected]> wrote:
> Hi all,
>
> After a few years of toying around with AVR I started experimenting with
> ARM using libopencm3. I got myself a cheap STM32 board and started coding.
> I was trying to get a very simple example working using a timer, ISR and a
> LED connected to a PWM port, and spent many hours not getting it to work.
>
> I've tried to adopt the example in
> 'libopencm3-examples/examples/stm32/f1/other/timer_interrupt' to my
> specific board using different GPIO and Maple's linker script, but no luck
> too.
>
> I've narrowed the code down to something that should toggle the onboard
> LED at 2Hz, yielding a 1Hz LED blinker. Unfortunately, the LED is shut off
> after the bootloader (Maple's DFU) finishes.
>
> I've created a Gist with my files:
> https://gist.github.com/jonkerj/e40e9b95f8e336c26a23
>
> I am not an expert on vector tables, but I find the generated vector table
> in my ELF binary rather suspicious for two reasons.
>
> First of all, I am trying to hook on TIM2's IRQ, which should be IRQ 28 on
> STM32 F1, according to ST's datasheet and libopencm3's json file. If we
> take a look into the objdump in the gist, we see that the vector table
> starts at 0x8005000. My ISR seems to be referenced at 0x80050b0 (that's IRQ
> 44, right?) and not at 0x8005070 (which is IRQ 28).
>
> Secondly, the vector table references the ISR routine "off by one": my ISR
> starts at 0x080051cc and the vector table jumps to 080051cd.
>
> I am a bit at loss if I am messing things up or if I'm running into a bug,
> so I was hoping a post to libopencm3's list could shed some light on this
> matter.
>
> Best regards,
>
> Jorik Jonker
>
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