Config and Pinout

[SteinC]

Hi, I'm using a WisBlock setup with:
• RAK19001 base board
• RAK4631 core
RAK18030 microphone in IO slot A
• RAK15002 microSD in IO slot B
I'm running Zephyr / nRF Connect SDK v3.2.4 on nRF52840.
The SD card works and WAV files are written correctly. The PDM driver also initializes and captures buffers successfully. However, the captured microphone data is not real audio. The raw blocks show a large startup transient, then an exponential decay, and then all samples become a constant value (around 7). Speaking or playing a tone directly into the microphone does not change the captured pattern.
We have already tested multiple PDM pin combinations in the Zephyr overlay, different channel selections, and also tried another microphone module. The behavior stays the same.
Could you please confirm the correct routing / pinapping / enable requirements for using RAK18030 on RAK19001 with RAK4631, specifically with RAK152 also installed in the other IO slot?

[Maria Gilje]

Hello, 

You need to ensure that the pins you are using are correctly configured. I.e. that NFC are pins configured as GPIOS with &uicr { nfct-pins-as-gpios; }; in your board overlay if you are using them, or that the module have the pins accessible/routed to the base board. Other than that you should be able to choose pins freely. 

May I ask if you are using some sample firmware for your application? I.e. the DMIC driver sample? Please note that the frequency settings need to be changed in main.c to reflect the frequencies the ones which the RAK18030 microphone supports. 

It is also possible to share your overlay to get a second opinion on it from me (or community members), but please note that I am not familiar with the WisBlock system, so I would need some time to get to know it to provide proper feedback. 

Best regards,

Maria

[SteinC]

Hi, thanks for swift answer, this is how our overlay looks like.: 

/ {

aliaser

disk0 = &sdhc0;

};

};

/* Aktiver PDM */

&pdm0 {

status = "ok";

pinctrl-0 = <&pdm0_standard>;

pinctrl-navn = "standard";

};

/* Definer PDM-pinner */

&pinctrl {

pdm0_standard: pdm0_standard {

gruppe1

psels = <NRF_PSEL(PDM_CLK, 0, 20)>,

<NRF_PSEL(PDM_DIN, 0, 19)>;

};

};

};

/* Aktiver SPI0 for SD-kort */

&spi0 {

status = "ok";

kompatibel = "nordisk, nrf-spim";

cs-gpios = <&gpio0 26 GPIO_ACTIVE_LOW>;

sdhc0: sdhc@0 {

kompatibel = "zephyr, sdhc-spi-spor";

reg = <0>;

status = "ok";

spi-maks-frekvens = <400000>;

mmc

kompatibel = "zephyr, sdmmc-disk";

disknavn = "SD";

status = "ok";

};

};

};

[Maria Gilje]

Hello, 

Thank you for your patience and for updating with the proper overlay file. 

Pins P0.20 and P0.19 are configured to uart0 by default. Where do you disable uart0 or change its pin configuration? Potentially, choose other pins for PDM if you are using uart0. 

If the pins are not the issue, verifying the PDM clock frequency is a good next step. 

Best regards,

Maria

[SteinC]

Hi , thanks for feedback. We are disabling uart0 in main because we have found that we need to "shut down" PDM after recording before starting up SD to write the recording-data.(SPI sync) We did this successflly with RAK11720 and a analog mic but are struggling with the PDM and the SD on this kit. We are using DMIC.  Have not been focusing on the PDM clock so far. We got some test software from RAK which they claime worked on this kit but it failed. Do you have some test routines that we could use just to verify the setup of this kit?

[SteinC]

Hi, thanks for feedback. We have now been able to use the mic and the SD card seperately but we are struggling to get them to be on the same SPI. We power down the PDM mic before turning the SD on and have ried several ways of setting timing between but it still seems to unstable. Do you have any hints or even test-software that can help us?  Thx Stein

[Maria Gilje]

Hi Stein, 

Thank you for your patience. 

SteinC said:

Do you have some test routines that we could use just to verify the setup of this kit?

We don't have any test conde for the RAK boards in general, but we have some tests for peripherals. I.e. the dmic_dump_buffer which tests a PDM microphone. It has an overlay for the nRF52840 DK which you can use as the basis for testing the PDM module on your RAK boards. 

SteinC said:

We have now been able to use the mic and the SD card seperately but we are struggling to get them to be on the same SPI. We power down the PDM mic before turning the SD on and have ried several ways of setting timing between but it still seems to unstable. Do you have any hints or even test-software that can help us?

Are there any pin conflicts for the SD card and microphone configurations which could explain why they work on their ownbut not together? You could i.e. inspect the built applications with the devicetree extension to investigate if there are any configurations which they share. 

Best regards,

Maria

[SteinC]

Hei, skriver på norsk siden ikke alt jeg skriver er god reklame for dere og jeg vil dere egentlig alt godt. Ganske imponert at dere har klart dere så bra i den sterke konkurransen som er på dette markedet. Dere var faktisk min kunde på slutten av 80 tallet :-) Så da skjønner du  sikkert at jeg ikke er helt nybegynner, selv om jeg har hatt roller som ikke direkte har vært å utvikle. Men litt kritikk: de pio som dere sender til meg er faktisk ikke korrekte, vi måtte til et referanseprpsjekt på RAK for å finne ut at det 04 og 21 som er riktig pinout på SD i vår config. Og i søken i databasen deres på PDM issues så har dere spørsmål som er 9år gamle som ikke er besvart !!! Ikke akkurat god reklame!! Det kan dere fikse lett!!. Så vår condig kjører komfortabelt nå, men vi sliter litt med strømforbruk. Pt , så klarer vi ikke få sleep til  under 950 µA med Zephyr Sleep. Har dere noe referansetall på denne config? Vet at vi kan gå til Power Off, men velger å teste ut uten.  Takk for hjelpen!! mvh Stein