How to Deploy AI Models to Microcontrollers

What You Need Before Starting

Deploying AI to an MCU requires three things: a trained model, a conversion pipeline, and a firmware project for your target hardware.

On the training side, you need a model that is small enough to fit in your MCU’s memory. For most microcontrollers, that means models under 500 KB. You will train on a desktop machine or cloud service — not on the MCU itself.

On the hardware side, you need:

• A supported MCU (ESP32, STM32, Arduino Nano 33 BLE, or similar ARM Cortex-M / Xtensa chip)
• The vendor’s toolchain installed (ESP-IDF for Espressif, STM32CubeIDE for ST, Arduino IDE for Arduino boards)
• A USB cable and basic embedded C experience

Step 1: Train or Select a Model

Start with a pre-trained model or train your own. For first deployments, use one of these proven starting points:

• Image classification: MobileNet V2 (quantized) — fits on ESP32-S3 with PSRAM
• Keyword spotting: The TFLite Micro speech example — runs on virtually any supported MCU
• Anomaly detection: A simple autoencoder or statistical model — under 20 KB on STM32F4

If you use Edge Impulse, the training and conversion happen in one pipeline. Upload your dataset, select a learning block, and Edge Impulse handles quantization and export.

If you use TensorFlow, train normally in Python, then convert to TFLite:

converter = tf.lite.TFLiteConverter.from_saved_model(saved_model_dir)
converter.optimizations = [tf.lite.Optimize.DEFAULT]
converter.target_spec.supported_types = [tf.int8]
tflite_model = converter.convert()

Step 2: Quantize to int8

Quantization converts 32-bit floating point weights to 8-bit integers. This is not optional for most MCUs — it reduces model size by 4x and speeds up inference significantly on chips without an FPU.

Full integer quantization (int8 weights and activations) is the standard for MCU deployment. You need a representative dataset — a small sample of real inputs — to calibrate the activation ranges:

def representative_dataset():
    for sample in calibration_data:
        yield [sample.astype(np.float32)]

converter.representative_dataset = representative_dataset
converter.target_spec.supported_ops = [tf.lite.OpsSet.TFLITE_BUILTINS_INT8]
converter.inference_input_type = tf.int8
converter.inference_output_type = tf.int8

Expect accuracy loss of 1-3% from quantization. If accuracy drops more than that, your model may be too complex for the target hardware.

Step 3: Convert to C Array

The MCU cannot read .tflite files from a filesystem. You convert the binary model into a C array that gets compiled into the firmware:

xxd -i model.tflite > model_data.cc

This produces a header with the model bytes:

unsigned char model_tflite[] = {
  0x20, 0x00, 0x00, 0x00, 0x54, 0x46, 0x4c, 0x33, ...
};
unsigned int model_tflite_len = 152384;

Edge Impulse skips this step — it exports a complete C++ library with the model already embedded.

Step 4: Set Up the TFLite Micro Runtime

Your firmware needs the TFLite Micro interpreter. The setup follows the same pattern regardless of MCU:

1. Include the runtime — add TFLite Micro source files to your build (as a static library or source inclusion)
2. Register operators — only the ops your model actually uses, keeping binary size small
3. Allocate a tensor arena — a static byte array that serves as the interpreter’s working memory
4. Load the model — point the interpreter at your C array
5. Run inference — copy input data into the input tensor, invoke, read the output tensor

The tensor arena size depends on your model. Start with 80-100 KB and reduce it until inference fails, then add 10% headroom.

Step 5: Flash and Test

Build the firmware and flash it to your board:

MCU	Build System	Flash Command
ESP32 / ESP32-S3	ESP-IDF	idf.py flash monitor
STM32H7 / STM32F4	STM32CubeIDE	Build + Run in IDE, or st-flash
Arduino Nano 33 BLE	Arduino CLI	arduino-cli upload -b arduino:mbed_nano:nano33ble

After flashing, verify inference works:

• Check serial output for prediction results
• Measure inference time — compare against your latency requirement
• Monitor RAM usage — the tensor arena plus stack must fit in available SRAM

Common Pitfalls

Model too large for flash. A 500 KB model on a 1 MB flash chip may not leave enough room for the firmware itself. Budget 40-60% of flash for application code and runtime.

Tensor arena too small. The interpreter will return kTfLiteError without a clear message. Increase the arena in 10 KB steps until inference succeeds.

Operator not supported. TFLite Micro supports a subset of TFLite operators. If your model uses an unsupported op (like FlexDelegate), you must restructure the model or implement the op manually.

Wrong input format. If your model expects int8 input but you feed float32 sensor data, results will be garbage. Match the input tensor type exactly.

Which MCU Should You Use?

The right choice depends on your use case:

Requirement	Recommended MCU	Why
Vision (camera input)	ESP32-S3	Camera interface, SIMD, PSRAM
Ultra-low power	STM32L4	< 100 nA shutdown mode
Maximum compute	STM32H7	480 MHz Cortex-M7, 1 MB SRAM
Budget / prototyping	ESP32-C3	$1-3 per chip, Wi-Fi included
Arduino ecosystem	Nano 33 BLE	Built-in sensors, simple IDE