pdm_resources.h

struct pdm_rx_resources_t

Collection of resources IDs required for PDM capture.

This struct is a container for the IDs of the XCore hardware resources used by the mic array unit’s PdmRx component for capturing PDM data from a port.

An object of this type will be used for initializing and starting the mic array unit.

Public Members

port_t p_mclk

Resource ID of the 1-bit port on which the master audio clock signal is received.

The master audio clock will be divided by a clock block to produce the PDM sample clock.

This port will be configured as an input.

port_t p_pdm_clk

Resource ID of the 1-bit port through which the PDM sample clock is signaled.

The PDM sample clock is used by the PDM microphones to trigger sample conversion.

This port will be configured as an output.

port_t p_pdm_mics

Resource ID of the port on which PDM samples are received.

In an SDR configuration, the number of microphone channels is the width of this port. In a DDR configuration, the number of microphone channels is twice the width of this port.

This port will be configured as an input.

unsigned mclk_freq

Master clock frequency.

Application’s master audio clock frequency in Hz. A typical value is 24576000 Hz

unsigned pdm_freq

PDM clock frequency.

Frequency in Hz of the physical PDM clock driving the microphones. This is the actual bit clock output to the PDM mics, not the PDM capture clock, which may differ when using DDR capture mode. Must be an integer factor of the MCLK frequency.

clock_t clock_a

used with mclk freq to calculate clock divider.

Resource ID of the clock block used to derive the PDM clock from the master audio clock.

In SDR configurations this is also the PDM data capture clock.

clock_t clock_b

Resource ID of the clock block used only in DDR configurations to trigger reads of the PDM data.

If operating in an SDR configuration, clock_b is 0. A value of 0 is what indicates an SDR configuration is being used.

PDM_RX_RESOURCES_SDR(P_MCLK, P_PDM_CLK, P_PDM_MICS, MCLK_FREQ, PDM_FREQ, CLOCK_A)

Construct a pdm_rx_resources_t for an SDR configuration.

pdm_rx_resources_t.clock_b is initialized to 0, indicating an SDR configuration.

Parameters:

  • P_MCLK – Master audio clock port resource ID.

  • P_PDM_CLK – PDM sample clock port resource ID.

  • P_PDM_MICS – PDM microphone data port resource ID.

  • MCLK_FREQ – MCLK frequency

  • PDM_FREQ – PDM frequency

  • CLOCK_A – PDM clock and capture clock block resource ID.

PDM_RX_RESOURCES_DDR(P_MCLK, P_PDM_CLK, P_PDM_MICS, MCLK_FREQ, PDM_FREQ, CLOCK_A, CLOCK_B)

Construct a pdm_rx_resources_t for a DDR configuration.

Parameters:

  • P_MCLK – Master audio clock port resource ID.

  • P_PDM_CLK – PDM sample clock port resource ID.

  • P_PDM_MICS – PDM microphone data port resource ID.

  • MCLK_FREQ – MCLK frequency

  • PDM_FREQ – PDM frequency

  • CLOCK_A – PDM clock clock block resource ID.

  • CLOCK_B – PDM capture clock block resource ID.