NN Model Loading Steps to RTL8735B

Arduino SDK – Load Model from Flash

Step 1: Rename network binary `.nb` file 

Please rename your customized .nb file into the expected filename to ensure successful loading. You may refer to the Default Supported Model Filenames section.

Step 2: Copy to Project Folder 

Windows: C:\Users\<USERNAME>\AppData\Local\Arduino15\packages\realtek\hardware\AmebaPro2\<VERSION>\libraries\NeuralNetwork\examples

Linux: /home/<USERNAME>/.arduino15/packages/realtek/hardware/AmebaPro2/<VERSION>/libraries/NeuralNetwork/examples

Step 3: Open Example 

E.g. File → Examples → AmebaNN → ObjectDetectionCallback

Step 4: Set Load Source 

E.g. Tools → NN Model Load from: → Load from Flash

Step 5: Update modelSelect()

ObjDet.modelSelect(OBJECT_DETECTION, CUSTOMIZED_YOLOV4TINY, NA_MODEL, NA_MODEL);

Step 6: Compile and Upload 

Click Upload in Arduino IDE. The .nb file is packaged into flash automatically.

Arduino SDK – Load Model from SD

Step 1: Rename `.nb` File 

Please rename your customized .nb file into the expected filename to ensure successful loading. You may refer to the Default Supported Model Filenames section.

Step 2: Open Example 

E.g. File → Examples → AmebaNN → ObjectDetectionCallback

Step 3: Set Load Source 

E.g. Tools → NN Model Load from: → Load from SD

Step 4: Update modelSelect()

ObjDet.modelSelect(OBJECT_DETECTION, CUSTOMIZED_YOLOV4TINY, NA_MODEL, NA_MODEL);

Step 5: Prepare SD card 

SD card root/
└── NN_MDL/
    └── yolov4_tiny.nb

Step 6: (Optional) Change SD Filename 

Edit SD_Model.cpp at: Arduino15\packages\realtek\hardware\AmebaPro2\<VERSION>\libraries\NeuralNetwork\src\SD_Model.cpp

static void *yolov4_get_SD_filename(void)
{
    return (void *)"sd:/NN_MDL/yolov4_tiny.nb";  // update filename here
}

Step 7: Compile, Upload, Insert SD Card 

Click Upload, then insert the SD card before pressing reset button.

FreeRTOS SDK – Load Model from Flash

Based on the mmf2_video_example_vipnn_rtsp_init YOLOv4 example.

Key Files

Table 9 Example of key files used in FreeRTOS SDK for loading customized model
File	Purpose
`component/file_system/nn/nn_file_op.c`	Controls flash vs SD loading
`mmf2_video_example_vipnn_rtsp_init.c`	Main example with USER_LOAD_MODEL block
`project/.../test_model/model_yolo.c`	Pre/post-processing for YOLO models

Step 1: Rename `.nb` File 

Please rename your customized .nb file into the expected filename to ensure successful loading. You may refer to the Default Supported Model Filenames section.

Step 2: Copy `.nb` into SDK 

project/realtek_amebapro2_v0_example/src/test_model/
└── model_nb/
    └── yolov4_tiny.nb    ← replace with your customized model

Step 3: Confirm MODEL_SRC is Flash (default)

In component/file_system/nn/nn_file_op.c:

#define MODEL_SRC  MODEL_FROM_FLASH   // default, no change needed

Step 4: Register Model in FWFS JSON 

Edit project/realtek_amebapro2_v0_example/GCC-RELEASE/mp/amebapro2_fwfs_nn_models.json:

{
    "msg_level": 3,
    "PROFILE": ["FWFS"],
    "FWFS": {
        "files": ["MODEL0"]
    },
    "MODEL0": {
        "name": "yolov4_tiny.nb",
        "source": "binary",
        "file": "yolov4_tiny.nb"
    }
}

Note

Only list models you actually use — unused models bloat the final image.

Step 5: Configure the Example 

In mmf2_video_example_vipnn_rtsp_init.c:

#define YOLO_MODEL      1
#define USE_NN_MODEL    YOLO_MODEL

#if (USE_NN_MODEL == YOLO_MODEL)
#define NN_WIDTH    416
#define NN_HEIGHT   416
static float nn_confidence_thresh = 0.4;
static float nn_nms_thresh = 0.3;
#endif

Enable the example in video_example_media_framework.c:

mmf2_video_example_vipnn_rtsp_init();

Step 6: Build 

cmake .. -G"Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=../toolchain.cmake -DVIDEO_EXAMPLE=ON
cmake --build . --target flash_nn

Output: flash_ntz.nn.bin in GCC-RELEASE/build/

Step 7: Flash to the Board 

Windows: uartfwburn.exe -p COM? -f flash_ntz.nn.bin -b 3000000 -U -x 32

Linux: ./uartfwburn.linux -p /dev/ttyUSB? -f ./flash_ntz.nn.bin -b 3000000 -U -x 32

FreeRTOS SDK – Load Model from SD Card

Based on the mmf2_video_example_vipnn_rtsp_init YOLOv4 example.

Key Files

Table 10 Example of key files used in FreeRTOS SDK for loading customized model
File	Purpose
`component/file_system/nn/nn_file_op.c`	Controls flash vs SD loading
`mmf2_video_example_vipnn_rtsp_init.c`	Main example with USER_LOAD_MODEL block
`project/.../test_model/model_yolo.c`	Pre/post-processing for YOLO models

Step 1: Rename `.nb` File 

Please rename your customized .nb file into the expected filename to ensure successful loading. You may refer to the Default Supported Model Filenames section.

Step 2: Prepare the SD Card 

SD card root/
└── NN_MDL/
    └── yolov4_tiny.nb

Step 3: Set MODEL_SRC to SD 

In component/file_system/nn/nn_file_op.c:

#define MODEL_FROM_FLASH  0x01
#define MODEL_FROM_SD     0x02
#define MODEL_SRC         MODEL_FROM_SD

Step 4: Enable USER_LOAD_MODEL in Example 

In mmf2_video_example_vipnn_rtsp_init.c, set USER_LOAD_MODEL to 1 and define the model object:

#define USER_LOAD_MODEL     1

#include "vfs.h"
static void *example_get_model_name(void)
{
    return (void *)"sd:/NN_MDL/yolov4_tiny.nb";
}

extern void yolov4_set_network_init_info(void *m);
extern int yolo_preprocess(void *data_in, nn_data_param_t *data_param, void *tensor_in, nn_tensor_param_t *tensor_param);
extern int yolo_postprocess(void *tensor_out, nn_tensor_param_t *param, void *res);
extern void yolo_set_confidence_thresh(void *confidence_thresh);
extern void yolo_set_nms_thresh(void *nms_thresh);

nnmodel_t yolov4_tiny_from_sd = {
    .nb                    = example_get_model_name,
    .set_init_info         = yolov4_set_network_init_info,
    .preprocess            = yolo_preprocess,
    .postprocess           = yolo_postprocess,
    .model_src             = MODEL_SRC_FILE,
    .set_confidence_thresh = yolo_set_confidence_thresh,
    .set_nms_thresh        = yolo_set_nms_thresh,
    .name = "YOLOv4t_SD"
};

Enable the example in video_example_media_framework.c:

mmf2_video_example_vipnn_rtsp_init();

Step 5: Build 

cmake .. -G"Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=../toolchain.cmake -DVIDEO_EXAMPLE=ON
cmake --build . --target flash_nn

Step 6: Flash to the Board 

Windows: uartfwburn.exe -p COM? -f flash_ntz.nn.bin -b 3000000 -U -x 32

Linux: ./uartfwburn.linux -p /dev/ttyUSB? -f ./flash_ntz.nn.bin -b 3000000 -U -x 32

Then, insert SD card before pressing the reset button.

Default Supported Model Filenames 

Category	Expected Filename
Object Detection	yolov3_tiny.nb yolov4_tiny.nb yolov7_tiny.nb
Face Detection	scrfd_500m_bnkps_640x640_u8.nb scrfd_500m_bnkps_576x320_u8.nb
Face Recognition	mobilefacenet_int8.nb mobilefacenet_int16.nb
Audio Classification	yamnet_fp16.nb yamnet_s_hybrid.nb
Image Classification	mobilenetv2_int16.nb img_class_cnn.nb
Hand Gesture	palm_detection_lite_int16.nb hand_landmark_lite_int16.nb

Note

For SD card loading, all files must be placed inside NN_MDL/ on the SD card: sd:/NN_MDL/<filename>.nb
For flash loading (Arduino SDK), filenames must match exactly and be placed in the NeuralNetwork examples folder
When running object detection + face detection simultaneously, use scrfd_500m_bnkps_576x320_u8.nb paired with yolov4_tiny_576x320.nb (same resolution)
mobilefacenet_int16.nb is preferred over int8 for better face recognition accuracy