Problem with Bluecoin and echo cancellation

[apenn.13]

Hy,

I'm trying to do some tests on echo suppression using evaluation boards BlueCoin and CoinStation.

The software I use is the one provided by ST to interact with BlueCoin that is, FP-"AUD-SMARTMIC1 GUI.exe" in addition to the

audacity.exe program.

As specified in the document , "Getting started with STM32Cube function pack for MEMS microphones acquisition, advanced audio

processing and audio output" (UM2219) paragraph 4.5, I would expect to hear on the output left only the signal picked up by

the microphone while on the right output the microphone signal plus the audio fragment.

I actually hear the microphone signal plus the audio fragment on both output left and right.

What should I do to hear on the output left only the microphone (and then have the proof that the echo cancellation worked) ?

The program loaded on the board BlueCoin is the version 1.0.0 ( Device presentation string: OSX SMARTMIC1 | BlueCoin Dev Kit |Embedded Microphones|1.0.0)

Thank you

[Eleon BORLINI]

Hi @apenn.13​ , to answer your question:

>> What should I do to hear on the output left only the microphone (and then have the proof that the echo cancellation worked)?

when the AEC feature is active, the "audio out" sends only the audio fragment, not the microphone, which is then cancelled by the AEC itself.

To check it is well working, you have to acquire the stream via USB and check if the audio fragment has been cancelled.

Regards

[apenn.13]

Hi,

thank you your answer.

My application also includes a low-cost product and I saw that echo canceller runs on the whole STM32F4 family. Can I also use 48-pin STM32F410CBT or 32K of ram is little? Are the necessary mips okay? The alternative would be STM32F401 but is it 64 pin?

Regards

[Eleon BORLINI]

Hi @apenn.13​ , sorry for the late answer. It is better to use at least an STM32F401RE, if it is not possible to use the Bluecoin STM32F446 180 MHz MCU. The HAL drivers are the same for the entire STM32F4xx, so you can try to run the same libraries on the STM32F410 (paying attention to the pin connections), but I cannot guarantee you the same performances / latency... Regards

[apenn.13]

Hi,

I tried echo cancellation with the bluecoin evaluation card and the SMARTMIC1 V2.0.0 application.

Everything seems to be working properly.

Now I would like to implement the echo deletion procedure on our card using the micro stm32f401re

and a mems microphone at a sampling rate of 8khz.

I wrote some code using the evaluation card stm32nucleo that mounts the micro stm32f401re since still our hw is not ready.

I realized that the execution of the process AcousticEC_Process that runs inside a low priority interrupt lasts about 8 msec

while in the bluecoin board that mounts a stm32f446 lasted about 300 usec.

The difference in process execution time seems to me to be excessive.

I would have expected a doubling of the time or a little more, since the micro works at 84 MHz while in the bluecoin it works at 168 MHz and

assuming that the dsp has the same characteristics in both cases.

Is there an explanation for this ?

Regards