sd_softdevice_enable return ram address instead of error code.

[LarsNLarsen]

The following is loaded into flash on the nRF52840:
Bootloader: 0xe0000
Application: 0x27000
SOFTDEVICE S140: 0x1000
MBR at 0x0000

Bootloader starts, waits 5 sec and runs the following:
sd_softdevice_vector_table_base_set(0x27000);
nrf_dfu_mbr_irq_forward_address_set(); /* Forward irq from mbr to softdevice */
app_start(0x27000);

Program counter arrives at the application.

If the application calls any sd_* functions the function will return some RAM address: ex: 0x2003ffbc
An example function could be:
uint32_t err_code:
sd_mbr_command_t mbr_cmd = { .command = SD_MBR_COMMAND_INIT_SD};
err_code = sd_mbr_command(&mbr_cmd);

err_code will have the value: 0x2003ffd0

If I remove the bootloader everything runs as expected.
I cannot find any return code which matches the 0x2003ffbc so it must be a RAM address.

[Vidar Berg]

Hello,

Please try to call app_start() with address 0x1000 instead of 0x27000. This should ensure that the SD's reset handler get executed before the main app is booted.

[LarsNLarsen]

Thank you for the quick answer.
You were right about the app_start call but it did not fix the issue.

The issue was that I first used this function before enabling the softdevice:

sd_mbr_command_t mbr_cmd = { .command = SD_MBR_COMMAND_INIT_SD};
err_code = sd_mbr_command(&mbr_cmd);

But as far as I understand, this command is not needed if you are using the sd_softdevice_enable function.

[Vidar Berg]

Thanks for reporting back. 'SD_MBR_COMMAND_INIT_SD' makes the MBR invoke the Softdevice by executing its reset handler and also start forwarding interrupts to it. Basically the same as calling nrf_dfu_mbr_irq_forward_address_set() followed by app_start(0x1000).

The 'SD_MBR_COMMAND_INIT_SD' command is only allowed to be called once, and only when the softdevice is not invoked. For instance, when you enable the Softdevice in the bootloader for OTA DFU.