Crate mendi 

mendi

Async Rust library for streaming fNIRS neurofeedback data from Mendi headbands over Bluetooth Low Energy.

Hardware

The Mendi headband is a consumer fNIRS (functional near-infrared spectroscopy) device that measures blood oxygenation in the prefrontal cortex. It communicates over BLE using protobuf-encoded messages on six GATT characteristics:

UUID	Characteristic	Data
0xABB1	Frame	IMU + temperature + 3 optical channels (IR/red/ambient)
0xABB2	Sensor	Optical sensor register read/write
0xABB3	IMU	IMU register read/write
0xABB4	ADC	Battery voltage, charging, USB status
0xABB5	Diagnostics	Self-test results at power-on
0xABB6	Calibration	LED current offsets, auto-cal, low-power mode

Quick start

use mendi::prelude::*;

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let client = MendiClient::new(MendiClientConfig::default());
    let (mut rx, handle) = client.connect().await?;

    while let Some(event) = rx.recv().await {
        match event {
            MendiEvent::Frame(f) => {
                println!("temp={:.1}°C  IR: L={} R={} P={}",
                    f.temperature, f.ir_left, f.ir_right, f.ir_pulse);
            }
            MendiEvent::Battery(b) => {
                println!("Battery: {:.2}V charging={}", b.voltage(), b.charging);
            }
            MendiEvent::Disconnected => break,
            _ => {}
        }
    }
    Ok(())
}

Module overview

Module	Purpose
mendi_client	BLE scanning, connecting, and the mendi_client::MendiHandle API
types	All event and data types produced by the client
protocol	GATT UUIDs and BLE constants
parse	Protobuf decoders for BLE notification payloads
wire	Generated protobuf types from device_v4.proto

Protobuf code generation

The wire module contains Rust types generated from proto/device_v4.proto using prost. By default, pre-generated code is bundled in src/wire_generated.rs so you do not need protoc installed.

To regenerate from the .proto file (e.g. after modifying it), enable the regenerate-proto feature:

cargo build --features regenerate-proto

This requires the protoc compiler to be available on your PATH. After regenerating, copy the output to src/wire_generated.rs to update the bundled version:

cp target/debug/build/mendi-*/out/mendi.rs src/wire_generated.rs

Feature flags

Feature	Description
simulate	Simulated + mock devices for testing without hardware
tui	Terminal UI with real-time charts (implies simulate)
regenerate-proto	Rebuild protobuf types from .proto (requires protoc)

Modules

mendi_client

BLE client for the Mendi neurofeedback headband.

parse

Protobuf decoders for Mendi BLE notification payloads.

prelude

Convenience re-exports.

protocol

GATT UUIDs and constants for the Mendi headband BLE protocol (V4).

types

Data types for events emitted by the Mendi BLE client.

wire

Generated protobuf types from the Mendi V4 wire protocol.