Hold Deadman switch pin during DFU enable

RE: Hold Deadman switch pin during DFU enable

LukeC — Tue, 10 Mar 2020 18:24:26 GMT

It looks like this is a bug in debug mode even in Rev 2. Going to SYSTEM_OFF does seem to fix this issue and preserve CNF registers, as long as you are not in debug mode.

https://infocenter.nordicsemi.com/topic/errata_nRF52840_Rev2/ERR/nRF52840/Rev2/latest/err_840.html

RE: Hold Deadman switch pin during DFU enable

LukeC — Tue, 10 Mar 2020 08:09:45 GMT

I think my issue is a Rev 1 errata issue.

It looks iike in Debug mode the CNF registers are cleared. I will test tomorrow with the debugger detached to see if that fixes the issue.

https://infocenter.nordicsemi.com/topic/errata_nRF52840_Rev1/ERR/nRF52840/Rev1/latest/err_840.html

RE: Hold Deadman switch pin during DFU enable

LukeC — Tue, 10 Mar 2020 05:57:28 GMT

Just to simplify things, I tried modifying a working example before the soft device was enabled to see if the GPIO registers would not reset to inputs when a SYSTEM_OFF event was received. I wanted to remove the bootloader from the equation, so this is just an app restarting after SYSTEM_OFF event.

I modified the ble_app_uart example with the following code at the begining of main():

// Setup Output pin and write to logic HIGH
nrf_gpio_cfg_output(9);
nrf_gpio_pin_write(9, true);

// Init logging
log_init();

// Init power managment
power_management_init();

// Setup always true sys off pin sense configuration 
nrf_gpio_cfg_sense_input(10, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_SENSE_HIGH);
nrf_gpio_cfg_sense_input(26, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_SENSE_HIGH);

// Enable SYSOFF
nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_GOTO_SYSOFF);

When I hit a breakpoint set at nrf_gpio_cfg_output(9) after the SYSOFF event, pin 9 is reset back to an input.

Is there another piece I am missing that will help me avoid the pin register reset issue?

Thanks!

RE: Hold Deadman switch pin during DFU enable

LukeC — Mon, 09 Mar 2020 21:13:03 GMT

Hung,

This possible solution looks very encouraging, but I cannot replicate the preservation of the GPIO pin registers with this method. Can you test this on your end?

In my application, I setup an always true sense pin to cause a latch event and call the power_system_off function. (Maybe there is a better way to force a SYSTEMOFF reset?)

 nrf_gpio_cfg_sense_input(10, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_SENSE_HIGH);
 
 #ifdef SOFTDEVICE_PRESENT
    if (nrf_sdh_is_enabled())
    {
        ret_code_t ret_code = sd_power_system_off();
#ifdef DEBUG
        while (true)
        {
            __WFE;
        }
#else
        ASSERT((ret_code == NRF_SUCCESS) || (ret_code == NRF_ERROR_SOFTDEVICE_NOT_ENABLED));
#endif
        UNUSED_VARIABLE(ret_code);
    }
#endif // SOFTDEVICE_PRESENT

    nrf_power_system_off();

I then set a breakpoint on the reset vector and at main in the DFU Boootloder.

I am definitely reseting using the SYSTEMOFF method as I check RESETREAS and can verify the register value and the correct GPRET value.

However, the deadman switch output NRF_P0->OUT gets cleared as well as PIN_CNF[17] is reset to an input (0x002).

It does look like the bootloader preserves the SENSE pin 10 setting, but all other pins are reset to inputs and the OUT register is reset to 0.

Questions:

1.) Are there any other settings I might have configured wrong? I remeoved 'CONFIG_GPIO_AS_PINRESET' from the bootloader and the app, but I don't think that should cause any issues.

2.) Do I have an early chip variant? My reads out 'AAC0'

RE: Hold Deadman switch pin during DFU enable

Hung Bui — Mon, 09 Mar 2020 14:35:30 GMT

Hi Luke,

You can use this trick described by this customer:

https://devzone.nordicsemi.com/f/nordic-q-a/49525/wake-from-system-off-mode-with-usb-vbus

Put the application to System OFF mode when a condition for waking up is already fulfill. This will trigger a reset immediately after CPU enters System_OFF.
And this type of reset is the only option that can preserve GPIO pins.

RE: Hold Deadman switch pin during DFU enable

LukeC — Sun, 08 Mar 2020 17:20:06 GMT

I will definitely get our hardware guy to add this on Rev 2, but we already have boards built.

I have all interrupts disabled before the jump so I don't think it is a peripheral interrupt. I am thinking it has something to do with the MBR, UICR or softdevice.

RE: Hold Deadman switch pin during DFU enable

Turbo J — Sun, 08 Mar 2020 07:05:26 GMT

[quote userid="18155" url="~/f/nordic-q-a/58843/hold-deadman-switch-pin-during-dfu-enable"] The pin drops low for about 2 ms, enough to disable the power switch.[/quote]

Just put an R+C low pass filter on the ouput pin.

Jumping into bootloader without resetting peripherials sounds rather dangerous, since most interrupts are NOT properly handled.