DFU with sd_power_system_off

[Simon]

Is it possible for an app after having gone to sd_power_system_off to reset by button without triggering DFU?

The app seems to need CONFIG_GPIO_AS_PINRESET to be set so that button p0.21 can get the app to advertise again, but when DFU is loaded, the advertise becomes DfuTarg. I was looking at invoking DfuTarg only when button p0.21 is pressed as power is being applied.

For DFU I tried enter_method_button 1 with enter_method_button_pin 21 (the app after system_off, button pressed goes to DfuTarg) , and separately enter_method_pinreset 0 (the app after system_off, no response with button pressed, but advertises app after power toggle but then no DFU).

-thank-you.

[Einar Thorsrud]

Hi,

You can check the RESETREAS register in the dfu_enter_check() function in the bootloader to see if the reset was caused by pin reset or power on reset. Note that you have to use sd_power_reset_reason_get() and sd_power_reset_reason_clr() instead of accessing the registers directly if you are using the SoftDevice (as is the case for the BLE bootloader). The RESETREAS value will be all 0 (0x00000000) if a power on reset occurred.

[Simon]

An available example would better help to understand if there is one.

-thank-you

[Einar Thorsrud]

Hi,

The following diff is for SDK 15 and demonstrates how it can be done. Please note that I have not tested it.

Fullscreen nrf_bootloader.c.diff Download

diff --git a/components/libraries/bootloader/nrf_bootloader.c b/components/libraries/bootloader/nrf_bootloader.c
index 3e62e47..d209ebf 100644
--- a/components/libraries/bootloader/nrf_bootloader.c
+++ b/components/libraries/bootloader/nrf_bootloader.c
@@ -58,6 +58,7 @@
 #include "nrf_bootloader_dfu_timers.h"
 #include "app_scheduler.h"
 #include "app_timer.h"
+#include "nrf_soc.h"
 
 static nrf_dfu_observer_t m_user_observer; //<! Observer callback set by the user.
 
@@ -272,8 +273,18 @@ static bool dfu_enter_check(void)
     if (NRF_BL_DFU_ENTER_METHOD_BUTTON &&
        (nrf_gpio_pin_read(NRF_BL_DFU_ENTER_METHOD_BUTTON_PIN) == 0))
     {
-        NRF_LOG_DEBUG("DFU mode requested via button.");
-        return true;
+        uint32_t reset_reason;
+        sd_power_reset_reason_get(&reset_reason);
+        sd_power_reset_reason_clr(~0);
+        if (reset_reason > 0)
+        {
+            NRF_LOG_DEBUG("Ignoring DFU button as device is not power cycled.");
+        }
+        else
+        {
+            NRF_LOG_DEBUG("DFU mode requested via button after power on reset.");
+            return true;
+        }
     }
 
     if (NRF_BL_DFU_ENTER_METHOD_PINRESET &&

 

[Simon]

By all accounts this should be working. The button on the custom is a tactile between p0.21 and GND. After flashing the bootloader and selecting FW, I toggle the power which makes reset_reason = 0. The FW is now advertising and by pressing the button, DfuTarg should now be advertising. But FW is still advertising. Maybe not understanding the sequence correctly.

[Einar Thorsrud]

There was a bug in the snippet, as I forgot to clear the RESETREAS register. I have updated the previous post so that it is cleared. Does it work with that update?

[Simon]

If the sequence is correct and updated to add sd_power_reset_reason_clr(~0);, it does not seem to want to return true, button pressed second time, FW advertises, power toggled, FW advertises then button pressed FW still advertises.
If I keep the original code in place, almost exact opposite to what is required is happening, with original when button pressed second time, DfuTarg advertises, when power toggled, FW advertises, and then button press, back to DfuTarg.
Maybe one other still detail missing in the dfu_enter_check?