Re: [OpenOCD-devel] STM32: Why does reading flash size fail after hard reset?

[Andreas F. <and...@gm...>]

On Sun, May 22, 2016 at 5:16 PM, Uwe Bonnes <
bo...@el...> wrote:

> Hello,
>
> starting openocd after a hardware reset for the first time, the sequence
>
> retval = target_read_u32(target, DBGMCU_IDCODE, &device_id);
> retval = target_read_u16(target, FLASH_SIZE_REG, &flash_size_in_kb);
>
> only succeeds for DBGMCU_IDCODE (0xE0042000), while the read for
> FLASH_SIZE_REG (0x1FFF75E0) fails. This happens with STLINK and
> Segger STLINK:
>
> jaylink: Failed to retrieve serial number: LIBUSB_ERROR_IO.
> Info : No device selected, using first device.
> Info : J-Link STLink V21 compiled Apr 15 2016 10:47:22
> Info : Hardware version: 1.00
> Info : VTarget = 3.300 V
> Info : clock speed 2000 kHz
> Info : SWD DPIDR 0x2ba01477
> Info : stm32f4x.cpu: hardware has 6 breakpoints, 4 watchpoints
> Info : accepting 'gdb' connection on tcp/3333
> Info : device id = 0x10006421
> Info : flash size = 8192kbytes
>
>
Could be because you have the chip in reset (connect_assert_srst for
example). I've seen on some variants that the flash is inaccessible under
reset, don't remember which family it was, perhaps L15x. I don't remember
seeing it on the F4.

Also the bogus value might be the ST-Link giving you garbage instead of
failure. Have you tried with a real JTAG/SWD adapter?

/Andreas