Hardware Guide
NXP's i.MX RT1062 excels at people counting via CMSIS-NN. The 1-core cortex-m7 at 600 MHz with 1024 KB SRAM handles 200 KB quantized models with 5.3x RAM headroom. Built-in Ethernet enables wireless result reporting.
| Spec | i.MX RT1062 |
|---|---|
| Processor | ARM Cortex-M7 @ 600 MHz |
| SRAM | 1024 KB |
| Flash | Up to 8 MB (external) |
| Key Features | Crossover MCU (600 MHz Cortex-M7), 1 MB on-chip SRAM (double of RT1052), L1 cache (32 KB I + 32 KB D), FlexRAM (configurable ITCM/DTCM/OCRAM), No on-chip flash (external QSPI/HyperFlash) |
| Connectivity | Ethernet, USB OTG HS/FS |
| Price Range | $6 - $12 (chip), $25 - $40 (dev board) |
With 1024 KB of internal SRAM, the i.MX RT1062 provides 5.3x the 192 KB minimum for people counting. This generous headroom means the 200 KB model tensor arena, sensor input buffers, and application logic (camera polling, Ethernet stack, state management) all fit without contention. The remaining 524 KB after model allocation supports complex application features. The i.MX RT1062 provides 8 MB of flash memory, which comfortably houses the CMSIS-NN runtime, the 200 KB model binary, application firmware, and OTA update partitions for field upgrades. Flash usage is well within budget for this configuration. The i.MX RT1062 runs at 600 MHz on a Cortex-M7 core, placing it among the higher-performance MCU options for ML inference. Its 1 MB SRAM and external memory interface support larger models including small vision networks. NXP's eIQ ML software provides optimized kernels for the RT series. People Counting requires camera input. The i.MX RT1062 lacks native peripheral support for some of these sensors, requiring external interface circuitry. A camera interface (DVP/DCMI) is not available — SPI-based camera modules may work but with reduced frame rates. Evaluate whether the peripheral gap justifies an alternative MCU with native support. CMSIS-NN provides ARM-optimized neural network kernels that leverage the i.MX RT1062's DSP instructions and floating-point unit for maximum inference throughput on Cortex-M. The kernels are hand-optimized in assembly for critical operations (Conv2D, DepthwiseConv2D, FullyConnected). Combine with TFLite Micro's CMSIS-NN delegate for the best performance on ARM targets. At $6-12 per chip ($25-40 for dev boards), the i.MX RT1062 offers strong value for people counting deployments. Key i.MX RT1062 features for this workload: Crossover MCU (600 MHz Cortex-M7), 1 MB on-chip SRAM (double of RT1052), L1 cache (32 KB I + 32 KB D), FlexRAM (configurable ITCM/DTCM/OCRAM), No on-chip flash (external QSPI/HyperFlash).
Set up i.MX RT1062 development environment
Install MCUXpresso IDE with the MCUXpresso SDK. Create a project targeting the i.MX RT1062 and verify basic functionality (blink LED, serial output). For CMSIS-NN, clone the framework repository and add it as a library dependency. Ensure the toolchain supports C++11 or later for the ML runtime.
Collect camera training data
Connect a camera module (e.g., OV2640 via DVP/SPI) to the i.MX RT1062. Write a data logging sketch that captures camera readings at the target sample rate and outputs via serial/SD card. Collect 1000+ labeled samples across all classes. Capture images at the model input resolution (96×96 or lower).
Train model and prepare for CMSIS-NN deployment
Train a quantized MobileNet-SSD or YOLO-Tiny in TensorFlow/Keras. Apply int8 post-training quantization via the TFLite converter — this is essential for CMSIS-NN's optimized kernels. The quantized model should be under 200 KB. Use tflite_micro's CMSIS-NN delegate to automatically route operations to optimized ARM kernels on the i.MX RT1062's cortex-m7 core.
Deploy and validate on i.MX RT1062
Include the CMSIS-NN runtime and compiled model in your NXP project. Allocate a tensor arena of 300-500 KB in a static buffer. Run inference on live camera data and compare predictions against your test set. Log results to serial for desktop validation. Measure inference latency and peak RAM usage to verify they meet application requirements.
STMicroelectronics cortex-m7 at 480 MHz with 1024 KB SRAM. $8-20 per chip. Excellent rated.
STMicroelectronics cortex-m7 at 216 MHz with 512 KB SRAM. $8-15 per chip. Compared to i.MX RT1062: less RAM but lower cost. Good rated.
STMicroelectronics cortex-m33 at 160 MHz with 786 KB SRAM. $6-15 per chip. Good rated.
Connect cameras to on-device inference — design detection workflows visually and compile to optimized firmware.
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