Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

Eliot Stock — Sat, 07 Jul 2018 05:03:31 GMT

In the end this was just down to me having made some changes in the application linker script without carrying them across to the bootloader linker script. But thanks everyone for the help.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

RK — Mon, 18 Jun 2018 23:06:49 GMT

of course you can set a breakpoint in the reset handler, set it by name or set it by address. Or use a better debugger than remote gdb, Segger Ozone is great at this stuff. Either way gdb, if pointed at a proper executable with debugging info can set a breakpoint on any line of any file.

Do you even have NOINIT defined in your memory map file? Are you getting link warnings?

And NOLOAD only deals with how a loader puts stuff into flash, it's really got nothing much to do with how the early runtime then copies stuff around into RAM or zeroes it out every time you reset. This is why you need to look at the early init code and see what it does with the various sections.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

Eliot Stock — Mon, 18 Jun 2018 21:58:32 GMT

Thanks, I made a bunch of edits above.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

Vidar Berg — Mon, 18 Jun 2018 13:04:44 GMT

good point. So should work if NOLOAD is used.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

RK — Mon, 18 Jun 2018 13:02:02 GMT

if .noinit isn't declared in sections, how does the code link without error?

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

Vidar Berg — Mon, 18 Jun 2018 12:17:17 GMT

As Austin mentioned, .noinit needs to be declared in SECTIONS as well (remember NOLOAD directive). But you could use NRF_LOG_FLUSH() if the goal is to empty the log buffer before reset.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

Austin — Mon, 18 Jun 2018 00:57:53 GMT

In addition to adding the extra segment to MEMORY, I believe you also need to add a SECTION directive and instruct the linker to direct your .noinit variables into NOINIT MEMORY area.

eg. Within the SECTION area of your linker script, add the following. As described in the comment for you existing linker script, ensure that your bootloader and any other program loader which runs before your app has a similar defined area which is not touched.

.noinit (NOLOAD) :
{
. = ALIGN(4);
__noinit_start__ = .;
*(.noinit*)
__noinit_end__ = .;
} > NOINIT

You can verify that your m_ram_log is in the correct memory location after linking by examining the map file or using nm on the linked binary to show symbol locations.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

hmolesworth — Sun, 17 Jun 2018 17:50:54 GMT

I tested this on my setup, and can confirm that NVIC_SystemReset() does not cause power to be removed from SRAM on the nRF52832; pity, maybe it is indeed the linker issue RK mentions. The sections and actual locations will be in the link map, of course. I do not see any RAM corruption with or without the above POWERSET setting.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

RK — Sun, 17 Jun 2018 02:00:25 GMT

what's it being reset to, 0? Where do you initialise the index pointer (or is the default for that 0 too)? You need to step through the early init code, the stuff called long before main, to see what it's doing with your noinit area and why. Just because you put it in section .noinit doesn't mean much unless your linker file puts that somewhere useful and your crt file doesn't overwrite it.

Put a breakpoint on the very first instruction after reset, the reset handler, and look at the contents of memory then. If it's correct, then your init code is overwriting it.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

Eliot Stock — Sat, 16 Jun 2018 21:08:09 GMT

Thanks. I've got the power on to the RAM, but I haven't aligned my buffer to the RAM areas. Will try that.

RE: Losing NOINIT RAM contents on a soft reset, nRF52832, SDK 14.0.0, gcc

hmolesworth — Sat, 16 Jun 2018 20:54:00 GMT

Not sure if this will help, but try keeping power applied to the particular RAM area you are using, which may be lost on a NVIC_SystemReset(). Also you might want to move the buffer so it aligns with a specific RAM location rather than overlapping two areas. Here's some code I use for this:

   // Set RAM power modes in system off
   NRF_POWER->RAM[7].POWERSET = (POWER_RAM_POWER_S0POWER_On     << POWER_RAM_POWER_S0POWER_Pos)      |
                                (POWER_RAM_POWER_S1POWER_On     << POWER_RAM_POWER_S1POWER_Pos)      |
                                (POWER_RAM_POWER_S0RETENTION_On << POWER_RAM_POWER_S0RETENTION_Pos)  |
                                (POWER_RAM_POWER_S1RETENTION_On << POWER_RAM_POWER_S1RETENTION_Pos);