This Arduino sketch can write Nintendo Power SF Memory cartridges without an external clock source like the Adafruit Clock Generator. It also uses the Arduino Serial Monitor instead of the OLED display and buttons.
In the Arduino IDE select the correct Serial Port under Tools then open the Serial Monitor, make sure the baud is set to "9600" and in the box in front of the baudrate there should be "No line ending" selected.
First send "8" via the text box and "Send" button at the top of the Serial Monitor windows. This will switch the cart to "hirom all" mode. It should give you the following feedback somewhere in the text box. Check that it did succeed:
Finally you can split the flash.bin file into the individual roms using the NP Split program: https://github.com/sanni/cartreader/tree/master/extras/npsplit
To flash something new you need to erase both the flash and the mapping first before you send the write command. Flashing the Nintendo Power Cart is more complicated since you need to provide it with a mapping.map and flash.bin file. You can create those files with the SF Memory Binary Maker: https://github.com/moldov/SF-Memory-Binary-Maker