Unexpected results with LL_ATON LL_ARITHACC AFFINE operation (AX + BY + C)

[yangweidage]

Hello, 

I am working with the LL_ATON library on STM32N6 and testing the LL_ARITHACC unit using the AFFINE operation, defined as: Output=A⋅X+B⋅Y+C.

I ran several tests with a simple network model whose only purpose is X + Y.

My expectation is:

• Case 1: A = 0, B = 0, C = 1
  → Output is correctly constant 1 as expected.

• Case 2: A = 1, B = 0, C = 0
  → Expected output = X, but the results are completely wrong and look like random values.

• Case 3: A = 0, B = 1, C = 0
  → Expected output = Y, but again the results are incorrect and look random

So, while the C_scalar works correctly, the usage of A_scalar and B_scalar does not produce the expected behavior.

Questions:

• Is there any special configuration needed in the switch/stream setup for X and Y inputs when using AFFINE?

The following screenshots are taken from the network.c file generated by the STEdgeAI compiler after compiling my simple X + Y tflite model. They show the configuration of the LL_ARITHACC unit for the AFFINE operation.

Thanks. 

[yangweidage]

Additional information:
The screenshot (see red box in main.c) shows how I initialized the input buffer to zero before running inference. This guarantees that both X and Y are all zeros during the test. However, the problem persists: With A=1, B=0, C=0 or A=0, B=1, C=0, the outputs are still incorrect and look random.

[yangweidage]

Problem solved. Before starting the first epoch that passes the inputs to the NPU through DMA, I forgot to clear the D-Cache.