Hi, I am using a STM32L496RE MCU and I am confused as to how the in_data should be formatted in the app_x_cube-ai.c file.

[Jf.1]

I have a model with 14 float inputs in a single array and 3 array output each with a size of 4 float numbers.

However the AI_input_size is ((1*1*14)*4) when I need it to be ((1*1*14)*1) and the AI_output_size is ((1*1*3)*4)

#define AI_NN1_IN_NUM       (1)
#define AI_NN1_IN { \
  AI_BUFFER_OBJ_INIT(AI_BUFFER_FORMAT_FLOAT, 1, 1, 14, 1, NULL), \
}
#define AI_NN1_IN_SIZE { \
  (1 * 1 * 14), \
}
#define AI_NN1_IN_1_SIZE  (1 * 1 * 14)
#define AI_NN1_IN_1_SIZE_BYTES  ((1 * 1 * 14) * 4)
 
 
 
 
#define AI_NN1_OUT_NUM      (3)
#define AI_NN1_OUT { \
  AI_BUFFER_OBJ_INIT(AI_BUFFER_FORMAT_FLOAT, 1, 1, 3, 1, NULL), \
  AI_BUFFER_OBJ_INIT(AI_BUFFER_FORMAT_FLOAT, 1, 1, 3, 1, NULL), \
  AI_BUFFER_OBJ_INIT(AI_BUFFER_FORMAT_FLOAT, 1, 1, 3, 1, NULL), \
}
#define AI_NN1_OUT_SIZE { \
  (1 * 1 * 3), \
  (1 * 1 * 3), \
  (1 * 1 * 3), \
}
#define AI_NN1_OUT_1_SIZE  (1 * 1 * 3)
#define AI_NN1_OUT_2_SIZE  (1 * 1 * 3)
#define AI_NN1_OUT_3_SIZE  (1 * 1 * 3)
#define AI_NN1_OUT_1_SIZE_BYTES  ((1 * 1 * 3) * 4)
#define AI_NN1_OUT_2_SIZE_BYTES  ((1 * 1 * 3) * 4)
#define AI_NN1_OUT_3_SIZE_BYTES  ((1 * 1 * 3) * 4)

I'm not sure how to insert the correct values as well as output and process them. The code above is the declarations of the model's outputs & inputs. How can I change or use them to produce my desired array sizes mentioned above.

The model inserted is a keras model with 1 input (array of 14 float values) and 3 outputs (each with an array of 3 values).

Thanks in advance

[Romain LE DONGE]

.

[Romain LE DONGE]

Hi,

You can use the size provided in this file this way:

In this example I was feeding accelerometer inputs to the network like that:

And using outputs this way: 

 

Best regards,

Romain

[Jf.1]

Hi,

Thank you for your reply, but can you explain further what is buffer length and why they need to be incremented when declaring the values for the in_data?

And for multiple outputs, do you have any suggestions as to how the values could be accessed? I am quite new to STM32 so I'm not familiar with how to implement this.

Many thanks

[Romain LE DONGE · Accepted solution]

Hi,

Sorry if I wasn't precise enough,

In the code above, in_data is the buffer I used to perform the network inference, I am just assigning values to the in_data buffer like a normal C array (using indices). Let's dig a little bit deeper into the process : In this code sample, you can see how to inject your data into the network and use the inference function "ai_network_run(...)".

• First I am declaring ai_buffer array to store input and output data. Those buffers are initialized using AI_NETWORK_IN and AI_NETWORK_OUT C Macros (generated in yournetwork.h file). I am also using the AI_NETWORK_IN/OUT_NUM here to create as many elements as there is of inputs/outputs.
• Then you need to fill some fields of the ai_buffer array. In the example I am setting a number of batch of 1, and I am specifying also the in_data buffer (the data you want to use) as you can see using the C Macro AI_HANDLE_PTR(...). In this example I have only one input and one output so I only configured ai_input[0] and ai_output[0], but in your usecase you would have to fill the 3 outputs you have: ai_output[0], ai_output[1], ai_output[2]. You can configure each output with AI_HANDLE_PTR using 3 different buffers or you can use a single one using C addresses to separates each outputs
• Finally once all your input and output buffers a configured correctly you can call "ai_network_run(...)" to perform the inference.

Hope it's clearer ! :)

Romain

[Jf.1]

Hi,

Thank you very much for the added information, I think it makes much more sense now with your clarification and I'm currently getting float values for the outputs.

Kind regards

[Khoo.B]

Hi,

I have the same question also. My input size as below:-

#define AI_NETWORK_AUDIO_AI_IN_1_HEIGHT   (32)

#define AI_NETWORK_AUDIO_AI_IN_1_WIDTH    (32)

#define AI_NETWORK_AUDIO_AI_IN_1_CHANNEL   (1)

#define AI_NETWORK_AUDIO_AI_IN_1_SIZE    (32 * 32 * 1)

#define AI_NETWORK_AUDIO_AI_IN_1_SIZE_BYTES (AI_NETWORK_AUDIO_AI_IN_1_SIZE * 4)

The size should be 32*32*1. But looking at the application template, it seems like I will need to use (32*32*1)*4. Why do we need multiplication of 4?

[jean-michel.d]

Hi,

AI_NETWORK_AUDIO_AI_IN_1_SIZE  indicates the total size of the input buffer in term of number of items/elements. AI_NETWORK_AUDIO_AI_IN_1_SIZE_BYTES  indicates the associated size in bytes. I suppose in your case that the type of data for the input is float, this explains the 4 ( = sizeof(float)).

AI_NETWORK_AUDIO_AI_IN_1_SIZE_BYTES  can be used to allocate or to define the input data buffer to store the input data.

If the buffer is allocated statically, you have two possibilities:

ai_float  in_data[AI_NETWORK_AUDIO_AI_IN_1_SIZE]
// or
AI_ALIGNED(4)   // to align the buffer on 4-byte boundary 
ai_unit8  in_data[AI_NETWORK_AUDIO_AI_IN_1_SIZE_BYTES];

Arrangement/layout of the data/items inside the buffer is dependent of the shape but it follows the standard C-definition for the arrays. See "C-memory layouts" section in the embedded documentation ("Embedded Inference Client API" article.

(typical location of the doc in the X-CUBE-AI pack: C:\Users\<user_name>\STM32Cube\Repository\Packs\STMicroelectronics\X-CUBE-AI\7.0.0\Documentation\index.html).

br,

Jean-Michel

[Khoo.B]

Thank you very much!