Sensor modules

AXS-027 — SPH0641LU4H-1 PDM microphone PMOD module

Catalog #27 in the AruviX sensor line, level L4 (PDM). Uses the Knowles SPH0641LU4H-1 instead of the catalog's original MP34DT06, which has no stock KiCad assets; it is the same 1-bit-PDM part class, so the CIC-decimator lesson is unchanged.

Level L4 ERC clean DRC clean Fab package 5 components

3D render of the AXS-027 PCB — Rendered from the PCB layout. No physical board has been manufactured.

Circuit review & bench-test guide →

Components#

Every placed component, with the reason it is on the board. Extracted directly from the schematic, so this cannot drift from the design.

Ref	Value	What it does on this board	Part number	Footprint
`C1`	100nF 16V X7R	VDD decoupling close to the microphone	`GRM188R71C104KA01D` Murata	`C_0603_1608Metric`
`J1`	PMOD PLUG 2x6	PMOD peripheral plug (Digilent spec 1.2)	not selected generic	`PinHeader_2x06_P2.54mm_Horizontal`
`JP1`	SELECT L/R	PDM slot select: 1-2 SELECT to GND = drive on clock-low half (default), 2-3 SELECT to VDD = drive on clock-high half	—	`SolderJumper-3_P1.3mm_Bridged12_RoundedPad1.0x1.5mm`
`R1`	100R	Series protection on the microphone-driven PDM data line	`RC0603FR-07100RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`U1`	SPH0641LU4H-1	Digital PDM MEMS microphone, bottom port, -26 dBFS, 64.3 dB SNR, multi-mode	`SPH0641LU4H-1` Knowles Datasheet ↗	`Knowles_LGA-5_3.5x2.65mm`

Signals#

Net labels used in the schematic, which are also the names the HDL top level should use.

3V3 CLK DATA GND MIC_DATA SEL

Production status#

Schematic ERC	0 violations
PCB layout	complete
DRC	0 violations
Fab package	exported (24 gerbers + drill + CPL + BOM)
Fabricated	no — design stage only

Source: boards/sensor-modules/axs-027-pdm-mic

Catalog #27 in the AruviX sensor line (../README.md), level L4 (PDM). Uses the Knowles SPH0641LU4H-1 instead of the catalog's original MP34DT06, which has no stock KiCad assets; it is the same 1-bit-PDM part class, so the CIC-decimator lesson is unchanged.

Status: schematic generated, ERC clean (0/0), netlist reviewed. PCB layout not started. Not released.

What it teaches#

The CIC-filter lesson: the host drives CLK at 1–3.2 MHz, the mic returns a 1-bit PDM stream, and the fabric builds the CIC decimator plus the droop-compensation FIR that recovers PCM audio. (The SPH0641LU4H-1 also has an ultrasonic mode up to 4.8 MHz for a stretch exercise.)

Design#

SPH0641LU4H-1, Knowles LGA-5, bottom port. 3V3 with 100 nF decoupling close to the mic.
Mic-driven DATA passes through a 100 Ω series resistor.
JP1 straps SELECT: 1-2 (default) = GND → the mic drives DATA during the clock-LOW half-cycle and tri-states during clock-high; 2-3 = VDD → clock-high half. Two mics strapped oppositely can share one DATA line (stereo PDM).

Custom PMOD map (documented here because it is neither a Digilent SPI nor I2C type — PDM is just clock out, data in):

PMOD pin	1	2	3	4	5	6	7	8	9	10	11	12
Net	DATA	NC	CLK	NC	GND	3V3	NC	NC	NC	NC	GND	3V3

Regenerate#

python3 generate_design.py

Remaining for release#

[ ] PCB layout (20 × 25 mm outline; bottom-side port hole kept clear of paste and copper pour), DRC, fab outputs
[ ] hdl/: PDM clock generator, CIC decimator + compensation FIR, testbench, ECP5 level-meter demo
[ ] BOM export and availability check, design-review checklist