The DFU inactivity timeout timer is a configurable timer implemented as a failsafe mechanism in the DFU. It prevents the device from being stuck in DFU mode indefinitely, which can happen if the controller cannot continue the DFU process, or if it is suddenly unavailable. In such case, the inactivity timeout timer will reset the device and go back to the previous state.

Note: Note that if there is no valid application present on the device, the reset due to inactivity timeout will immediately put the target in DFU mode after reset.

Configuring the inactivity timeout timer

You can configure the inactivity timeout timer by modifying the configuration parameter NRF_DFU_INACTIVITY_TIMEOUT_MS in the sdk_config file. The value you set is the number of milliseconds before the device resets due to inactivity timeout.

The default configuration is 120 seconds (in ms):

sdk_config.h
|#ifndef NRF_DFU_INACTIVITY_TIMEOUT_MS
|#define NRF_DFU_INACTIVITY_TIMEOUT_MS 120000
|#endif

For details on editing the SDK configuration, see SDK configuration header file.

Note: To disable the inactivity timeout timer, set the value of the timeout to a very large number.