RoyalBlue54L Feather

The RoyalBlue54L Feather's development started as soon as nRF54L15 modules were available. The advantages of the 54L vs. the older 52 series are pretty massive, significantly better performance (128MHz vs. 64MHz) and expanded memory (1.5MB vs 1MB at max). Unfortunately (and sort of fortunately as well!) the nRF54L15 does not have a USB peripheral onboard. This means that it's not possible to use something like Adafruit's UF2 bootloader.

At first, I considered using the Silicon Labs CP2102 USB<->UART bridge IC:

However, the CP2102 can only do one thing! It can only act as a UART bridge. What if we used another, cheaper IC that could also act as a debugger?

This is where the nRF52833 enters. (Certainly, there are other ICs that could serve this purpose, but Nordic stuff is comfortable for me to use!)

This part has plenty of memory for this use-case (debugger + UART bridge). The QFN-48 package was chosen for ease of assembly. This is also one of the only Nordic parts I am aware of that has USB pins available in a QFN. The firmware for the debugger is available on my GitHub!

Power is managed with the nPM1300 PMIC. This includes two buck regulators (200mA each) and two LDOs that can also function as load switches. A ship mode pin is broken out on the wildcard Feather pin as well. This IC handles battery charging and fuel gauging too! It greatly simplified the overall design of the system as compared to a discrete solution.

There are a few other small items onboard. A level shifter connects the debugger and nRF54L15 so that the target can also operate at 1.8V (as configured by the nPM1300). There is a small external SPI flash chip, an NFC connector, and a Qwiic/STEMMA QT connector to easily interface with Adafruit or Sparkfun devices.

Since the nRF54L15 supports Zephyr, it should also be possible to get both MicroPython and Arduino Core running on these devices, although this work is still pending.

For more info on the RoyalBlue54L Feather, be sure to subscribe to the CrowdSupply page here: https://www.crowdsupply.com/lords-boards/royalblue54l-feather