StackMemo

A simple spaced repetition system for M5Stack Core2 devices and similar (anything with an ESP32, some storage and a screen would do) based on the SuperMemo2 algorithm.

Functionality

Provided a python file qa.py with questions and answers as the one provided as an example, this will automatically generate (on the device, as you answer questions) a file memos.json with intervals and ease factors for each question, as you answer them.

Note Why a python file and not a json file? No particular good reason. I started with python and left it like that, it works.

The UI is simple:

• Turn off button: the button on top left; saves the current SuperMemo weights and powers off the device. It sleeps for a couple of seconds just in case something needs flushing. You never know.
• Show answer: only available in questions, of course. Shows the answer and enables right/wrong buttons. Also hides the power button because answers tend to be more verbose than questions.
• Right/wrong: only available in answers. Depending on what you pick, it will update the SuperMemo weights internally. Right uses q=4.5 (almost perfect, perfect would be 5) and wrong uses q=2 (quite wrong but not horribly wrong)
• Question/answer area: click it to show question information (it's actually just a large button):
  • n: number of times you have answered this question.
  • ef: ease factor for this question.
  • i_n: next "interval".
  • c: counter for number of questions answered in this session (until a restart)
  • F: number of questions marked as "to fix"

When in Info mode (after tapping the question/answer area) the off button hides and a very large button with To fix appears. This lets you mark a question as needing editing. This is appended to a file to_edit.json and you can interact with it with some gmake commands.

Questions are shown starting from the smallest interval, but I don't use the Core2 RTC, I just keep showing questions ordered by i_n. Hacky: it won't give the full benefits of spaced repetition unless you "stop reviewing". But kind of gets the job done in showing "worse" questions first, which is what I wanted.

There is some minor reformatting of markdown tags in questions and answers, where *, _ and ``` are used to change text colors.

Note Sometimes it hangs on start or on power off, seems to only happen while plugged to a computer. I'm not sure if there's a bug in the to_edit functionality, or I didn't test it well enough in the first iteration. But if it happens, a hardware (button, either reset or long-press to power off) or software (gmake reset) fixes it. It only seems to happen at start time, so no data loss.

Installing

You need to get some form of micropython with lvgl on your board. In my case, I used this one.

Next, easiest is to install adafruit-micropython (see here) and execute make upload device=DEVICEPATH, device path will be something like /dev/….

Some images

Question	Information	Answer

Algorithm

This thingy uses SuperMemo 2:

Algorithm SM-2, © Copyright SuperMemo World, 1991.

https://www.supermemo.com https://www.supermemo.eu "