FatFS on ESP32 wasn't well documented, or usable, so I learned about it, and made some changes to the esp32-arduino core:
ffat, data, fat, 0x111000,0x2EF000,
If you pull https://github.com/espressif/arduino-esp32/ master and select esp32-dev, you will see easy to select partition splits for code vs FFat.
More details here: https://github.com/marcmerlin/esp32_fatfsimage/blob/master/README.md , and at the top level, there is a pre-generated fatfsimage that lets you build a fatfs image:
# replace 3004 with the size of your partition. In the 1/3MB split, the fatfs partition is
# 0x2EF000 = 3076096 . 3076096/1024 = 3004
fatfsimage -l5 img.ffat 3004 datadir
Once the image is built
esptool.py --chip esp32 --port /dev/ttyUSB0 --baud 921600 write_flash 0x111000 img.ffat
I put together some code you can run to verify the partition list and get a file listing: https://github.com/marcmerlin/esp32_fatfsimage/blob/master/arduino/ffat/ffat.ino .
Here is the output:
partition addr: 0x010000; size: 0x100000; label: app0
partition addr: 0x009000; size: 0x005000; label: nvs
partition addr: 0x00e000; size: 0x002000; label: otadata
partition addr: 0x110000; size: 0x001000; label: eeprom
partition addr: 0x111000; size: 0x2ef000; label: ffat
Trying to mount ffat partition if present
File system mounted
Total space: 3018752
Free space: 1429504
Listing directory: /gifs64
FILE: /gifs64/ani-bman-BW.gif SIZE: 4061
FILE: /gifs64/087_net.gif SIZE: 46200
More details and code here: https://github.com/marcmerlin/esp32_fatfsimage
The FFAT module uses 8KB plus 4KB per concurrent file that can be opened. By default, it allows 10 files to be opened, which means it uses 48KB. IF you want to reduce its memory use, you can tell it to only support one file, and you will save 36KB, leaving you with only 12KB used.
if (!FFat.begin(0, "", 1)) die("Fat FS mount failed. Not enough RAM?");
Newer Solution, Consider this Instead
After I wrote all this, a better solution came up: https://github.com/lorol/arduino-esp32fs-plugin I recommend you install this instead and then grab a mkfatfs binary (it's a bit of a pain to build) from:
grab esp32fs.jar from https://github.com/lorol/arduino-esp32fs-plugin/releases
This will integrate with the arduino GUI and likely do what you want. That said, if you'd like to create your FatFS image from a makefile and upload it via esptool, then my repo explained above, does this fine.
I've then improved AnimatedGIFs to add support for FatFS/FFat which nicely fixes the short hangs I was getting with SPIFFS, which was ruining the animations: