I/O modules

AXO-015 — potentiometer + slider bank PMOD module

Catalog #15 in the AruviX output line, level L3. The "analog input fun" board: two rotary thumb pots and a real slide pot, all digitized by an MCP3008.

Level L3 ERC clean DRC clean Fab package 17 components

3D render of the AXO-015 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`	10nF 50V X7R	RC shunt on the pot 1 wiper: fc ~ 16 kHz	`GRM188R71H103KA01D` Murata	`C_0603_1608Metric`
`C2`	10nF 50V X7R	RC shunt on the pot 2 wiper: fc ~ 16 kHz	`GRM188R71H103KA01D` Murata	`C_0603_1608Metric`
`C3`	10nF 50V X7R	RC shunt on the slider wiper: fc ~ 16 kHz	`GRM188R71H103KA01D` Murata	`C_0603_1608Metric`
`C4`	100nF 16V X7R	VDD decoupling	`GRM188R71C104KA01D` Murata	`C_0603_1608Metric`
`C5`	100nF 16V X7R	VREF decoupling	`GRM188R71C104KA01D` Murata	`C_0603_1608Metric`
`C6`	1uF 10V X7R	Supply bulk decoupling	`GRM188R71A105KA61D` Murata	`C_0603_1608Metric`
`J1`	PMOD PLUG 2x6	PMOD peripheral plug (Digilent spec 1.2)	not selected generic	`PinHeader_2x06_P2.54mm_Horizontal`
`J3`	CH3 SPARE	Spare analog input: CH3 + GND return	not selected generic	`PinHeader_1x02_P2.54mm_Vertical`
`R1`	1k	RC series element on the pot 1 wiper	`RC0603FR-071KL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R2`	1k	RC series element on the pot 2 wiper	`RC0603FR-071KL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R3`	1k	RC series element on the slider wiper	`RC0603FR-071KL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R4`	10k	~CS idle pull-up so an unconfigured host cannot start a conversion	`RC0603FR-0710KL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R5`	100R	Series protection on the ADC-driven DOUT line	`RC0603FR-07100RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`RV1`	10k ROTARY	Rotary thumb pot 1: full-rail, wiper to CH0	`PT10MV10-103A2020-S` Piher Datasheet ↗	`Potentiometer_Piher_PT-10-V10_Vertical`
`RV2`	10k ROTARY	Rotary thumb pot 2: full-rail, wiper to CH1	`PT10MV10-103A2020-S` Piher Datasheet ↗	`Potentiometer_Piher_PT-10-V10_Vertical`
`RV3`	10k SLIDE	Slide pot (20 mm travel): full-rail, wiper to CH2	`PTA2043-2015CPB103` Bourns Datasheet ↗	`Potentiometer_Bourns_PTA2043_Single_Slide`
`U1`	MCP3008	8-channel 10-bit SAR ADC, SPI, 200 ksps	`MCP3008-I/SL` Microchip Datasheet ↗	`SOIC-16_3.9x9.9mm_P1.27mm`

Signals#

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

3V3 ADC_DOUT CH3 CS_N GND MISO MOSI POT1 POT1_W POT2 POT2_W SCK SLIDE SLIDE_W

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/io-modules/axo-015-pots

Catalog #15 in the AruviX output line (../README.md), level L3. The "analog input fun" board: two rotary thumb pots and a real slide pot, all digitized by an MCP3008.

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

What it teaches#

Three continuously-variable human inputs: mixer faders, synth knobs (with the DDS module axo-010), RGB color mixing on the LED bar, PID setpoint twiddling. Same SPI ADC protocol as axs-031, so the HDL carries over.

Part picks (verified against stock KiCad 9 libraries)#

Rotary (RV1, RV2): Piher PT-10 vertical — footprint Potentiometer_THT:Potentiometer_Piher_PT-10-V10_Vertical (stock, pads 1/2/3), MPN PT10MV10-103A2020-S (10 k linear). Chosen over the catalog's TC33X suggestion: the TC33X is a screwdriver trimmer, not finger-adjustable; the PT-10 vertical takes a thumbwheel/shaft.
Slide (RV3): a stock slide-pot footprint EXISTS — Potentiometer_THT:Potentiometer_Bourns_PTA2043_Single_Slide (pads 1/2/3 + MP), so the catalog's "substitute a third rotary" fallback is not needed. MPN PTA2043-2015CPB103 (10 k linear, 20 mm travel). Symbol Device:R_Potentiometer_MountingPin carries the MP pad, tied to GND.
ADC: Analog_ADC:MCP3008 (8-ch 10-bit SPI, proven in axs-031), MCP3008-I/SL, SOIC-16.

Channel plan#

MCP3008	CH0	CH1	CH2	CH3	CH4–CH7
Source	pot 1	pot 2	slider	spare on J3 (1×02, with GND)	grounded

Each wiper passes 1 k + 10 nF (fc ≈ 16 kHz) before its channel — scratch filter plus SAR charge reservoir. CH4–CH7 are grounded so no SAR input ever floats. VREF = VDD = 3V3: knob position maps linearly to the 10-bit scale.

Support parts per platform convention: 10 k ~CS idle pull-up, 100 Ω on the ADC-driven DOUT→MISO line, 100 nF on VDD and VREF + 1 µF bulk.

PMOD pin map (Type 2 SPI)#

PMOD pin	1	2	3	4	5	6	7	8	9	10	11	12
Net	CS_N	MOSI	MISO	SCK	GND	3V3	NC	NC	NC	NC	GND	3V3

Regenerate#

python3 generate_design.py

Remaining for release#

[ ] PCB layout (pots on the outer edge for finger clearance; slider travel axis along the board), DRC, fab outputs
[ ] hdl/: reuse the axs-031 MCP3008 read core; 3-channel scan demo
[ ] BOM export and availability check, design-review checklist