Using Elixir Nerves IoT Framework for Traditional Straw-Wrapped Natto Making

#elixir #iot #raspberrypi #japan

Introduction

"Natto making?" on a tech platform? I know what you're thinking. Don't rush to judgment. Sometimes articles like this are worth reading. Some invisible thread of fate brought you here, so please stay and enjoy this journey.

The Year 2025

2025 was a tumultuous year, called the "Reiwa Rice Crisis" by some. While many traditional media outlets predicted that the politician known for their "rice policy commitment" would become the next Prime Minister, Japan instead saw its first female Prime Minister take office. History is told by historians of later generations, and we won't know the true significance for 10 or 100 years, but 2025 may have been a turning point.

I'm writing this as if it has deep meaning for someone reading this 100 years from now. These are just the thoughts of an ordinary citizen. I hope future historians will take note.

My 2025

Bringing this back to my personal life, I became deeply absorbed in three things this year:

Shogi (Japanese chess)
Kiyoshi Yamashita
Rice farming

For shogi, I finally reached 1-dan rank on Shogi Wars. It took me 9 years. I devoted almost every day to shogi, mainly focusing on tsumeshogi (chess problems). However, since I used the "chess god" feature occasionally to advance, my current 1-dan achievement rate is below 20% - what's called "underground." When you hit 100% at 1-kyu, you advance to 1-dan, which equals 20% at 1-dan.

https://note.com/awesomey/n/n3523082881bf

I realized something important: I have virtually no talent for shogi. Some people learn the rules and breeze through to 1-dan, while others like me take 9 years. The same is true in technology - some people learn a bit of syntax and immediately build applications, while others struggle to grasp programming concepts. I've been in this field for over 20 years now. Though I'm far from the top, I've become so accustomed to basic programming concepts that I've lost touch with what beginners find difficult. When beginners ask fundamental questions, I'm not mature or patient enough - I get irritated, it shows in my attitude, and I've intimidated many newcomers. I feel terrible about this, but I can't change the past.

What does this have to do with shogi? Well, reaching 1-dan means you can easily beat someone who just knows how the pieces move, but among all shogi players, it's about average skill. There are always stronger players above, and throughout a single game, I make many mistakes that would prompt questions like "Why can't you solve a 9-move problem?" "Why did you miss that checkmate?" "Why did you make such a strange move?" Fortunately, my teachers are books and YouTubers - I don't attend classes where someone would actually say these things to me. But it suddenly struck me: isn't this exactly what I've been doing when teaching programming? While strictness has its place in teaching, perhaps I was demanding too high a level from beginners. Yet I also want them to easily surpass my level. Otherwise, Japan will remain behind, unable to recover from the "lost 30 years." I'm speaking in grand terms here. My individual efforts won't change anything, but I think struggling is what it means to live. That's my philosophical conclusion.

Let me digress. Wander, if you will. I found a compilation of diaries by Kiyoshi Yamashita, the genius wandering artist, at my local library. I devoured it. Fascinating. Free-spirited, natural. Persistent. Patient. That's why he left behind such masterpieces. I dare to call him "Kiyo-chan," as his close friends did. I want to be free like Kiyo-chan, honest enough to get upset if I don't get two servings of curry rice - genuine with no pretense. During his wanderings, Kiyo-chan would ask for "musubi" (rice balls). The main ingredient is, of course, rice. Incidentally, Kiyo-chan also loved shogi.

As mentioned earlier, this year became known as the Reiwa Rice Crisis. By chance, I participated in pesticide-free rice farming done entirely by traditional hand methods - planting, harvesting with sickles, everything the old way. It was just an experience. I only worked for about half a day over three days total. That's nowhere near enough to speak about agriculture. I only understood how hard it is. My mentors, Antonio Inoki and Yoshida Shōin, had rich interactions with soil and nature during their sensitive childhood years. I have a feeling that these formative experiences connected to their later great achievements. I can't yet explain this connection well with words, but I trust this intuition is fundamentally correct. When I can articulate that "something" that connects them, I'll share it again.

Back to the topic. Rice planting, summer weeding, autumn harvesting - just three days of experience, but in this year of the "Reiwa Rice Crisis," I feel something mysterious. When you grow rice without pesticides and hang the stalks cut with sickles, they become straw, which is essential for natto-making. The pesticide-free aspect is key.

Traditional Straw-Wrapped Natto Making

Reference: Traditional Natto Making Method Using Straw (with Precautions)

This article provides detailed instructions:

Soak soybeans in water (24 hours)
Boil soybeans (6 hours)
Sterilize straw in boiling water
Keep soybeans with straw at around 40°C (24 hours)
Let rest in refrigerator (24 hours)

I believed step 4, temperature control, was the most critical. I maintained temperature using hot water bottles and glass bottles filled with hot water inside a styrofoam box. Inside the box, I placed a Raspberry Pi 4 with an AHT20 temperature/humidity sensor to monitor the temperature. The software running on the Raspberry Pi 4 was an application built with Nerves, an IoT framework for Elixir.

All source code is available at https://github.com/TORIFUKUKaiou/hello_iot_cloud2023

hello_nerves is the Nerves app flashed to Raspberry Pi 4
aht20_tracker is an API server + Grafana visualization module built with Phoenix, an Elixir web framework

Normally, this device somewhat aimlessly measures the temperature and humidity in my room. But when placed in the styrofoam box, it faithfully and accurately sent temperature data to the API server.

And here's the finished straw-wrapped natto. It was delicious. I think even Qiitan (Qiita's mascot) said it looked tasty.

Conclusion

I reflected on 2025 - how I viewed this year and the events in my life.

Managing temperature control for traditional straw-wrapped natto making with a Nerves application - this was completely Nerves-related content, so I posted it to the "#NervesJP Advent Calendar 2025."

Recently, I've been absorbed in the TV anime "Oishinbo." I'll write about that along with the state of the world in next year's Advent Calendar 2026.