AODMIC Application (app/aodmic-app.c)

Table of Contents

• Prerequisites
• Operation
• Jetson TX2
• Jetson AGX Xavier

The AODMIC application demonstrates how to operate Always On (AON) DMIC from the SPE/AON processor. AODMIC is in the AON domain for both Jetson TX2 and Jetson AGX Xavier. The compilation of this demo app can be controlled by the ENABLE_AODMIC_APP flag in the soc/*/target_specific.mk file. The ENABLE_GPCDMA_FUNC flag must also be enabled.

Prerequisites

Stereo PDM mics should be connected to the AODMIC pins on the respective Jetson platform. An example PDM mic part is https://www.mouser.in/datasheet/2/389/mp34dt01-m-955068.pdf. Details of the AODMIC pins are mentioned in the platform specific sections further down.

Operation

The app runs continuously and captures data from AODMIC using GPCDMA. It periodically prints the R5 CPU tick count and the zero crossing count (on both capture channels). These counts can be used to determine whether the AODMIC is running at the expected rate. The app also computes and prints the capture volume over fixed periods (computed as the mean square of the samples). Should the computed volume exceed a predefined threshold, it triggers system wake.

The command below may be executed on the running target in order to trigger system suspend:

# sudo systemctl suspend

After the system is placed in the suspended state, making a loud sound near the AODMIC mics should wake it up.

Note

To demonstrate system wake, the corresponding wake event must be enabled by CCPLEX/BPMP. In this case the wake event is wake83. When the system goes to suspend state, the BPMP UART reports enabled masks of the wake events in the log. Verify that in this log bit 83 is set, both in the wake mask and in the Tier2 routing mask. For example:

WAKE_MASK[95:64] = 0x1ff200
TIER2[95:64] = 0xff200

The threshold for system wake may need to be modified so that it is neither too high nor too low relative to the general volume of the captured audio.

The AODMIC test app is currently configured for 16 kHz with stereo channels. It may be modified to capture at any of the supported AODMIC rates. OSR is fixed at 64.

Jetson TX2

AODMIC signals are available at the 40-pin header J21 with these pin mappings:

• Pin 16 - DMIC5_DAT (CAN_GPIO0)
• Pin 32 - DMIC5_CLK (CAN_GPIO1)

Note

Pinmux must be set for the J21 pins by following the instructions in TX2 Developer Guide.

Jetson AGX Xavier

AODMIC signals are available at the 40-pin header J30 with these pin mappings:

• Pin 16 - DMIC5_DAT (CAN1_STB)
• Pin 32 - DMIC5_CLK (CAN1_EN)

Note

Pinmux must be set for the J30 pins by following the instructions in AGX Xavier Developer Guide.

If the system is placed in suspended state, BPMP is likely to disable the dmic5 clock at the subsequent system wake, upon which AODMIC capture will fail. You can patch this in either of two ways:

• On the running target execute:

  # sudo su
  # sudo echo 1 > /sys/kernel/debug/bpmp/debug/clk/dmic5/state

  or
• Patch the platform BPMP DT file (e.g. tegra194-a02-bpmp-p2888-a04.dtb) following these steps:
  • Reconstruct the device tree source file from the DTB:

    $ dtc -I dtb -O dts <BPMP DT file> -o <temp_file.dts>
    

  • Patch the third and fourth arguments to the 'dmic5' entry in the generated temp_file.dts file (third argument = <sample_rate*64>):

    clocks {
        lateinit {
            dmic5 = <0x86 0x5b 1024000 0x80000>;
        };
    };
    

  • Recreate the DTB file from the patched DTS:

    $ dtc -I dts -O dtb <temp_file.dts> -o <BPMP DT file>
    

  • Flash the bpmp-fw-dtb partition, or perform a full flash.