Sensor modules

AXS-038 — TTP223 capacitive-touch PMOD module

Catalog #38 in the AruviX sensor line, level L1 (single GPIO). The TTP223 has no stock KiCad symbol, so the generator embeds a custom symbol block (SOT-23-6 pin table from the Tontek datasheet) and emits a project-local AruviX_AXS.kicad_sym + sym-lib-table, following the pattern.

Level L1 ERC clean DRC clean Fab package 8 components

3D render of the AXS-038 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	U1 VDD decoupling	`GRM188R71C104KA01D` Murata	`C_0603_1608Metric`
`C2`	10pF C0G (DNP) DNP	Sensitivity trim capacitor, 0-50 pF range; fit/adjust to tune (larger C = less sensitive)	`GRM1885C1H100JA01D` Murata	`C_0603_1608Metric`
`J1`	PMOD PLUG 2x6	PMOD peripheral plug (Digilent spec 1.2)	not selected generic	`PinHeader_2x06_P2.54mm_Horizontal`
`J2`	TOUCH PAD	Touch-electrode attachment point (wire, foil, or PCB pad)	not selected generic	`PinHeader_1x01_P2.54mm_Vertical`
`JP1`	AHLB MODE	Open (default) = output active-high; bridge to 3V3 = active-low	—	`SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mm`
`JP2`	TOG MODE	Open (default) = momentary output; bridge to 3V3 = toggle (latch) mode	—	`SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mm`
`R1`	100R	Series protection on the sensor-driven output line	`RC0603FR-07100RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`U1`	TTP223-BA6	Single-key capacitive touch detector, SOT-23-6	`TTP223-BA6` Tontek Datasheet ↗	`SOT-23-6`

Signals#

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

3V3 AHLB GND TOG TOUCH TOUCH_PAD TOUCH_Q

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-038-touch

Catalog #38 in the AruviX sensor line (../README.md), level L1 (single GPIO). The TTP223 has no stock KiCad symbol, so the generator embeds a custom symbol block (SOT-23-6 pin table from the Tontek datasheet) and emits a project-local AruviX_AXS.kicad_sym + sym-lib-table, following the boards/usb-c-pd-trigger pattern.

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

What it teaches#

The simplest sensor in the line: one debounced GPIO level. The FPGA lesson is input synchronizers (2-FF), debouncing, edge detection, and toggle logic — and, on the hardware side, what a capacitive electrode is.

Design#

Tontek TTP223-BA6, SOT-23-6. Pin table: 1 Q, 2 VSS, 3 I (sense), 4 AHLB, 5 VDD, 6 TOG.
Sense electrode: J2, a 1×1 pin-header pad (PinHeader_1x01) as the wire/foil attachment point on net TOUCH_PAD, wired to pin 3.
Sensitivity: C2 10 pF C0G, DNP, from TOUCH_PAD to GND. The TTP223 accepts 0–50 pF; fit/adjust to desensitize a large or cabled electrode (larger C = less sensitive).
Mode straps: AHLB and TOG have internal pull-downs and sample at power-on. JP1/JP2 are open solder jumpers to 3V3:
both open (default) = momentary, active-high output;
bridge JP1 (AHLB=1) = active-low output;
bridge JP2 (TOG=1) = toggle/latch mode.
Q passes a 100 Ω series resistor (R1) to PMOD pin 1 as TOUCH.

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

Regenerate#

python3 generate_design.py   # also rewrites AruviX_AXS.kicad_sym + sym-lib-table

reports/erc.rpt is the last kicad-cli ERC run.

Remaining for release#

[ ] Decide the shipped electrode (on-board copper pour pad vs. J2 wire) at layout; keep the sense trace short and away from the PMOD bus
[ ] PCB layout, DRC, fab outputs
[ ] hdl/: synchronizer/debounce/edge-detect core, testbench, ECP5 demo
[ ] BOM export and availability check, design-review checklist