What is it?

Macronix's MX25L12835FZNI 128 Mbit 104 MHz flash memory using SPI to communicate with your Ladybug or Butterfly. The board is designed to mount directly onto the Ladybug or Butterfly and is such a small size that it won't interfere with other add-ons like radios or motion sensors. It can be used in the breadboard but 3V3 and GND are supplied at the top edge of the add-on board and you will have to use jumper wires to make use of these add-ons on the breadboard.

Note: the there are two options since the Ladybug and Butterfly development boards have different widths. So make sure you choose the correct option for your development board when ordering.

The 3V3-only boards have a 100 nF bypass capacitor to reduce high-frequency noise and a 100K pullup on the CS lines to reduce chip select problems. Here is an SPI test sketch which makes using these chips very easy! Here is a primer on how SPI works in general.

There are write protect and hold (both active low) broken out on the board but for standard SPI and general use these are not needed. That means you can continue to use the I2C port that aligns with these pins as long as you do not connect them (solder them) to the board.

These are very fast chips. They take about 400 microseconds to read/write a 256-byte page and about 40 seconds to erase the entire chip. The read/write time is between 10 and 20 times faster than EEPROM.

The Macronix flash is also very low power; it uses only 2 uA in the low power mode, which the Ladybug Arduino core enables unless SPI.begin is specifically called.

Why did you make it?

Everyone understands the need for compact data logging solutions. SD Cards are fine if you have the space, power, and it doesn't cause problems with other peripherals. This isn't always the case. I started with EEPROMS, which are very low power and super easy to use, but they only provide at most 2 Mbits of data storage. This is enough for several minutes of motion sensor data logging, but there are many applications where this isn't enough.

These SPI Flash memory chips increase the available storage by orders of magnitude. If 2 Mbit of EEPROM can log a 100 Hz data stream for five minutes, the 128 Mbit flash can do so for 5 hours. That's a lot of data!

What makes it special?

These are appallingly small boards that are designed to be soldered directly to your Ladybug or Butterfly for fast and deep data logging applications. They can be used standalone on a breadboard also, but mounted on your Ladybug or Butterfly is where they shine enabling low-power, fast, and portable data logging for many applications.

The cool thing about Ladybug, Butterfly, and Dragonfly (and the STM32L4 in general) is that we have implemented the USB/MSC protocol in the Arduino core meaning that the SPI flash add-on can appear as a mass storage device to your laptop; select USB+mass storage in the Arduino IDE and any memory device attached to the development board will show up as a disk drive on your computer. This means you can drag and drop files onto the SPI flash (or SD card) from the laptop and vice versa and transfer data via the USB cable. What could be easier?!

Order the boards from OSH Park and assemble some of your own, or order the fully assembled and tested board from me and see what you can do with 16 Mbytes of fast memory!