esp-embassy-config

A crate for storing data on persistent flash on esp32 devices. This can us used for storing information like wifi ssid/password, some url to connect to etc. An uart menu is used to list and update this config.

ConfigEntry

A static arrays of ConfigEntry objects has to be passdd is passed to an ConfigMenu object. This means that the config setup is defined at compile time, which makes sense for a embedded project. In the examples this is done with StaticCell, which possibly could be improved with a macro.

// setup config menu
static ENTRIES: StaticCell<[ConfigEntry; 2]> = StaticCell::new();
static CONFIG_MENU: StaticCell<Mutex<CriticalSectionRawMutex, ConfigMenu>> = StaticCell::new();
let entries = ENTRIES.init([
    ConfigEntry::new("value", 16, "What is this value?", false),
    ConfigEntry::new("long_value", 32, "What is this other value?", true),
]);
let config_menu = CONFIG_MENU.init(Mutex::new(ConfigMenu::new(entries, encoded_key, aes)));

Notice that the "2" in the first line has to match the number of entries.

The ConfigEntry has:

• name, which is the identifier of the entry.
• n_blocks, which is the number of 16 bytes blocks that is used for storage.
• offset, which is calculated by the ConfigMenu.
• question, which is the question the menu system will ask when updating the entry.
• secret, which when true, will never display the content of the entry, just as stars

Encryption

The information is AES encrypted before its written to flash. This is not intended to be an absolute secure solution, but to prevent things like wifi password to be stored in clear text on flash. The key for the encryption is a hash created from a supplied key

• a hard coded salt. How the key is supplied is up to the user, importing it from an enviroment variable is one possibility.

Features

wifi

The wifi feature adds some default entries to the config, and a menu item for connecting to wifi. This makes it easy to store wifi password (relatively) safely on the device, and connect using the esp-embassy-wifihelper crate. It is still possible to add your own custom entries, the wifi ones will just be there as well.

Adding the wifi dependencies adds significant build time and flash size (flash time), so if its not needed, it should probably be skipped.

Examples

config_uart

Simple project for testing out how the menu works.

config_wifi

A project that demonstrate the wifi feature, and connects to wifi using esp-embassy-wifihelper crate with the information stored in the config.