I am currently sourcing hardware for an IoT project. The deadlines are tight so I plan to use RAK WisBlock components, specifically the RAK13102 Blues Note Carrier. This carrier only has I2C wired. The MCU shall be a nRF52840 (RAK4631) running MCUboot and Zephyr.
In the first paragraph of your guide to NOFU it states that
The bootloader can load and execute code from a variety of sources including Flash, RAM, UART, USB, I2C, or SPI.
however it then only goes on to mention UART configuration.
The issue I face is that RAK just confirmed neither the UART nor the RESET/BOOT pins are connected on their carrier and suggested soldering the required 0 Ohm SMD resistors.
I will be deploying quite a few of these devices and obviously I am hoping to do as little soldering as possible! I saw that I2C DFU was possible with the old DFU method but haven’t found anything related to I2C with NOFU.
No, this is not possible. For outboard DFU (where the Notecard manages the entire host DFU process) the wiring requires the Notecard’s ALT_DFU (or AUX) pins to be connected to the host’s UART pins. This is because the Notecard’s internal firmware transfers the firmware image over UART. You can find more details on this in the guide linked below:
The alternative would be implementing host-managed DFU yourself (referred to as inboard (IAP) DFU). This involves adding code to your nRF52840 to instruct the Notecard to download the firmware file from Notehub and then handling the application of the firmware update within your MCU. However, given your tight deadlines, I wouldn’t recommend this approach as it requires additional development effort, especially when the Notecard already provides a seamless and reliable solution.
For quick prototyping, my recommendation is to use the Notecarrier F with an Adafruit nRF52840 Feather Express. We have a comprehensive guide detailing how this setup works and how the Notecard can upgrade firmware via MCUboot:-