EFUSE to store user application data

[blavoie]

I'm creating an ESP32 soft AP project and I'm serving up a few webpages. I would like to add a webpage which allows a UI for network settings. I'd like to expose some of the network configurations to the user, such as SSID name and password. I'm also considering exposing the DHCP pool range and base IP settings, but I haven't decided yet.

Instead of adding external flash, I am considering using the ESP32 internal EFUSE. The datasheet doesn't provide a lot of detail, but apparently its 1Kbits in size where the first 256 bits hold the MACID and other ESP32 related data and the remaining bits can be accessed from the user application. With the network settings I'm considering, that may be enough.

I'm hoping someone would have done this already and can explain how to access the application storage space without disrupting the ESP32 chip data. Any help is greatly appreciated.

[ESP_igrr]

EFUSE is one time programmable. Is it your intention to make network settings of a device unchangeable for the entire lifetime of the device?

Edit: "eFuse controller" chapter of the ESP32 Technical Reference Manual mentions that BLOCK3 of EFUSE is reserved for user purposes. This block has width of 128/192/256 bits, depending on the redundancy parameter ("coding scheme") configured. The TRM also gives instructions for programming and reading EFUSE bits.

[WiFive]

This is what NVS is for http://esp-idf.readthedocs.io/en/latest ... flash.html