When the trigger library is added to an application, it allows a connected USB host to remotely tell the app to reboot into the bootloader to allow it to be updated via DFU. When asked to enter bootloader mode, it pulls its own reset pin using the GPIO pin
BSP_SELF_PINRESET_PIN (by default, only available on PCA10059). As a consequence, the library requires the following:
The experimental Open USB bootloader example is configured in this way, and newer versions of the nRF Connect PC app are equipped to communicate with the Trigger module.
We recommend setting the USB serial number with app_usbd_serial_num_generate (see also note below). This allows the host to follow the device as it transitions from application to bootloader, since the bootloaders have the same serial number.
This library is similar to the Runtime part of the USB DFU 1.1 spec, but differs in the following way:
|DFU_DETACH||0x00||None, reboots into bootloader.|
|Firmware Info||0x07||Information structure, see app_usbd_nrf_dfu_trigger_nordic_info_t|
|Version String||0x08||"[application name] [semantic_version]"|
The default [semantic version] is "0.1.0+MMM-DD-YYYY-HH-MM-SS", where the timestamp is the time of compilation. The application name and version can be set via sdk_config.