Once you successfully trained or imported a model, you can use Edge Impulse to download a C++ library that bundles both your signal processing and your machine learning model. Until recently, we could only run one impulse on MCUs.
This tutorial is for advanced users. We will provide limited support on the forum until this feature is fully integrated into the platform. If you have subscribed to an Enterprise plan, you can contact our customer success or solution engineering team.
In this tutorial, we will see how to run multiple impulses using the downloaded C++ libraries of two different projects.
We have put together a that will automate all the processes and provide a C++ library that can be compiled and run as a standalone.
In this page, we will explain the high level concepts of how to merge two impulses. Feel free to look at the code to gain a deeper understanding.
Multi-impulse vs multi-model vs sensor fusion
Running multi-impulse refers to running two separate projects (different data, different DSP blocks and different models) on the same target. It will require modifying some files in the EI-generated SDKs.
Running multi-model refers to running two different models (same data, same DSP block but different tflite models) on the same target. See how to run a motion classifier model and an anomaly detection model on the same device in .
Sensor fusion refers to the process of combining data from different types of sensors to give more information to the neural network. See how to use sensor fusion in .
Also see this video (starting min 13):
Examples
Make sure you have at least two impulses fully trained.
You can use one of the following examples:
Audio + Image classification
This example can be used for an intrusion detection system. We will use a first model to detect glass-breaking sounds, if we detected this sound, we will then classify an image to see if there is a person or not in the image. In this tutorial, we will use the following public projects:
Merge multiple impulses into a single C++ Library
By default, the quantized version is used when downloading the C++ libraries. To use float32, add the option --float32 as an argument.
Similarly by default the EON compiled model is used, if you want to use full tflite then add the option --full-tflite and be sure to include a recent version of tensorflow lite compiled for your device architecture in the root of your project in a folder named tensorflow-lite
If you need a mix of quantized and float32, you can look at the dzip.download_model function call in generate.py and change the code accordingly.
By default, the block will download cached version of builds. You can force new builds using the --force-build option.
Locally
Retrieve API Keys of your projects and run the generate.py command as follows:
Build the container:docker build -t multi-impulse .
Then run:docker run --rm -it -v $PWD:/home multi-impulse --api-keys ei_0b0e...,ei_acde...
Custom deployment block
Initialize the custom block - select Deployment block and Library when prompted:edge-impulse-blocks init
Push the block:edge-impulse-blocks push
Then go your Organization and Edit the deployment block with:
CLI arguments: --api-keys ei_0b0e...,ei_acde...
Privaliged mode: Enabled
Understanding the process
If you have a look at the generate.py script, it streamline the process of generating a C++ library from multiple impulses through several steps:
Library Download and Extraction:
If the script detects that the necessary projects are not already present locally, it initiates the download of C++ libraries required for edge deployment. These libraries are fetched using API keys provided by the user.
Libraries are downloaded and extracted into a temporary directory. If the user specifies a custom temporary directory, it's used; otherwise, a temporary directory is created.
Customization of Files:
For each project's library, the script performs several modifications:
At the file name level:
It adds a project-specific suffix to certain patterns in compiled files within the tflite-model directory. This customization ensures that each project's files are unique.
Renamed files are then copied to a target directory, mainly the first project's directory.
At the function name level:
It edits model_variables.hfunctions by adding the project-specific suffix to various patterns. This step ensures that model parameters are correctly associated with each project.
Merging the projects
model_variables.h is merged into the first project's directory to consolidate model information.
The script saves the intersection of lines between trained_model_ops_define.h files for different projects, ensuring consistency.
Copying Templates:
Generating Custom Code:
The script retrieves impulse IDs from model_variables.h for each project. Impulses are a key part of edge machine learning models.
Custom code is generated for each project, including functions to get signal data, define raw features, and run the classifier.
This custom code is inserted into the main.cpp file of each project at specific locations.
Archiving for Deployment:
Finally, the script archives the target directory, creating a zip file ready for deployment. This zip file contains all the customized files and code necessary for deploying machine learning models on edge devices.
When changing between projects and running generate.py locally:
You may need to include the --force-build option to ensure correctness of the combined library.
Compiling and running the multi-impulse library
Now to test the library generated:
Download and unzip your Edge Impulse C++ multi-impulse library into a directory
Copy a test sample's raw features into the features[] array in source/main.cpp
Enter make -j in this directory to compile the project. If you encounter any OOM memory error try make -j4 (replace 4 with the number of cores available)
Enter ./build/app to run the application
Compare the output predictions to the predictions of the test sample in the Edge Impulse Studio
Want to add your own business logic?
You can change the template you want to use in step 4 to use another compilation method, implement your custom sampling strategy and how to handle the inference results in step 5 (apply post-processing, send results somewhere else, trigger actions, etc.).
Limitations
General limitations:
The custom ML accelerator deployments are unlikely to work (TDA4VM, DRPAI, MemoryX, Brainchip).
The custom tflite kernels (ESP NN, Silabs MVP, Arc MLI) should work - but may require some additional work. I.e: for ESP32 you may need to statically allocate arena for the image model.
In general, running multiple impulses on an MCU can be challenging due to limited processing power, memory, and other hardware constraints. Make sure to thoroughly evaluate the capabilities and limitations of your specific MCU and consider the resource requirements of the impulses before attempting to run them concurrently.
Use case specific limitations:
The model_metadata.hcomes from the first API Key of your project. This means some #define statement might be missing or conflicting.
Object detection: If you want to run at least one Object Detection project. Make sure to use this project API KEY first! This will set the #define EI_CLASSIFIER_OBJECT_DETECTION 1 and eventually the #define EI_HAS_FOMO 1. Note that you can overwrite them manually but it requires an extra step.
Anomaly detection: If your anomaly detection model API Key is not in the first position, the model-parameter/anomaly_metadata.h file will not be included.
Visual anomaly detection AND time-series anomaly detection (K-Means or GMM): It is currently not possible to combine two different anomaly detection models. The #define EI_CLASSIFIER_HAS_ANOMALY statement expect ONLY one of the following argument:
If you see an error like the following, you probably used twice the same API Key:
Project ID is 517331
Export ZIP saved in: temp/517331/cubes-visual-ad-v12.zip (6218297 Bytes)
Project ID is 517331
Traceback (most recent call last):
File "generate.py", line 49, in <module>
os.makedirs(download_path)
File "/Users/luisomoreau/.pyenv/versions/3.8.10/lib/python3.8/os.py", line 223, in makedirs
mkdir(name, mode)
FileExistsError: [Errno 17] File exists: 'temp/517331'
Make sure you use distinct projects.
Manual procedure
When we first wrote this tutorial, we explained how to merge two impulses manually; This process is now deprecated due to recent changes in our C++ SDK, some files and functions may have been renamed.
See the legacy steps
Some files and function names have changed
The general concepts remain valid but due to recent changes in our C++ inferencing SDK, some files and function names may have changed.
Download the impulses from your projects
Head to your projects' deployment pages and download the C++ libraries:
Make sure to select the same model versions (EON-Compiled enabled/disabled and int8/float32) for your projects.
Extract the two archive in a directory (multi-impulse for example).
Rename the tflite model files
Rename the tflite model files:
Go to the tflite-model directory in your extracted archives and rename the following files by post-fixing them with the name of the project:
for EON compiled projects: tflite_learn_[block-id]_compiled.cpp/tflite_learn_[block-id]_compiled.h.
for non-EON-compiled projects: tflite_learn_[block-id].cpp/tflite_learn_[block-id].h.
Rename the variables in the tflite-model directory
Rename the variables (EON model functions, such as trained_model_input etc. or tflite model array names) by post-fixing them with the name of the project.
e.g: Change the trained_model_compiled_audio.h from:
#ifndef tflite_learn_5_GEN_H
#define tflite_learn_5_GEN_H
#include "edge-impulse-sdk/tensorflow/lite/c/common.h"
// Sets up the model with init and prepare steps.
TfLiteStatus tflite_learn_5_init( void*(*alloc_fnc)(size_t,size_t) );
// Returns the input tensor with the given index.
TfLiteStatus tflite_learn_5_input(int index, TfLiteTensor* tensor);
// Returns the output tensor with the given index.
TfLiteStatus tflite_learn_5_output(int index, TfLiteTensor* tensor);
// Runs inference for the model.
TfLiteStatus tflite_learn_5_invoke();
//Frees memory allocated
TfLiteStatus tflite_learn_5_reset( void (*free)(void* ptr) );
// Returns the number of input tensors.
inline size_t tflite_learn_5_inputs() {
return 1;
}
// Returns the number of output tensors.
inline size_t tflite_learn_5_outputs() {
return 1;
}
#endif
to:
#include "edge-impulse-sdk/tensorflow/lite/c/common.h"
// Sets up the model with init and prepare steps.
TfLiteStatus tflite_learn_audio_init( void*(*alloc_fnc)(size_t,size_t) );
// Returns the input tensor with the given index.
TfLiteStatus tflite_learn_audio_input(int index, TfLiteTensor* tensor);
// Returns the output tensor with the given index.
TfLiteStatus tflite_learn_audio_output(int index, TfLiteTensor* tensor);
// Runs inference for the model.
TfLiteStatus tflite_learn_audio_invoke();
//Frees memory allocated
TfLiteStatus tflite_learn_audio_reset( void (*free)(void* ptr) );
// Returns the number of input tensors.
inline size_t tflite_learn_audio_inputs() {
return 1;
}
// Returns the number of output tensors.
inline size_t tflite_learn_audio_outputs() {
return 1;
}
#endif
Tip: Use an IDE to use the "Find and replace feature.
Here is a list of the files that need to be modified (the names may change if not compiled with the EON compiler) in folders for both projects:
tflite-model/tflite_learn_[block-id]_compiled.h
tflite-model/tflite_learn_[block-id]_compiled.cpp
Rename the variables and structs in model-parameters/model_variables.h
Be careful here when using the "find and replace" from your IDE, NOT all variables looking like _model_ need to be replaced.
Create a new directory (merged-impulse for example). Copy the content of one project into this new directory (audio for example). Copy the content of the tflite-model directory from the other project (image) inside the newly created merged-impulse/tflite-model.
The structure of this new directory should look like the following:
The section that should be copied is from const char* ei_classifier_inferencing_categories... to the line before const ei_impulse_t ei_default_impulse = impulse_<ProjectID>_<version>.
Make sure to leave only one const ei_impulse_t ei_default_impulse = impulse_233502_3; this will define which of your impulse is the default one.
Subtract and merge the trained_model_ops_define.h or tflite_resolver.h
Make sure the macros EI_TFLITE_DISABLE_... are a COMBINATION of the ones present in two deployments.
For EON-compiled projects:
E.g. if #define EI_TFLITE_DISABLE_SOFTMAX_IN_U8 1 is present in one deployment and absent in the other, it should be ABSENT in the combined trained_model_ops_define.h.
For non-EON-Compiled projects:
E.g. if resolver.AddFullyConnected(); is present in one deployment and absent in the other, it should be PRESENT in the combined tflite-resolver.h. Remember to change the length of the resolver array if necessary.
In this example, here are the lines to deleted:
The source code and the generator script can be found .
See documentation for more details about custom deployment blocks.
The script copies template files from a templates directory to the target directory. The template available includes files with code structures and placeholders for customization. It's adapted from the example available on Github.
If you see the following segmentation fault, make sure to
This feature is a developer preview. Changes and improvements can still be made without prior notice and there are no guarantees that this feature will be fully released in future.
