Lab modules

AXL-009 — GPIO expander lab PMOD module (MCP23017)

Catalog #9 in the AruviX lab line, level L3. The I2C register-map lesson with instantly visible results — and pin multiplication for big projects (16 IO for 2 PMOD data pins).

Level L3 ERC clean No layout No fab package 38 components

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 decoupling	`GRM188R71C104KA01D` Murata	`C_0603_1608Metric`
`C2`	10uF 10V X5R	Module bulk (8 LEDs switching)	`GRM21BR61A106KE19L` Murata	`C_0805_2012Metric`
`D1`	GREEN	GPA0 indicator LED	`APT1608SGC` Kingbright Datasheet ↗	`LED_0603_1608Metric`
`D2`	GREEN	GPA1 indicator LED	`APT1608SGC` Kingbright Datasheet ↗	`LED_0603_1608Metric`
`D3`	GREEN	GPA2 indicator LED	`APT1608SGC` Kingbright Datasheet ↗	`LED_0603_1608Metric`
`D4`	GREEN	GPA3 indicator LED	`APT1608SGC` Kingbright Datasheet ↗	`LED_0603_1608Metric`
`D5`	GREEN	GPA4 indicator LED	`APT1608SGC` Kingbright Datasheet ↗	`LED_0603_1608Metric`
`D6`	GREEN	GPA5 indicator LED	`APT1608SGC` Kingbright Datasheet ↗	`LED_0603_1608Metric`
`D7`	GREEN	GPA6 indicator LED	`APT1608SGC` Kingbright Datasheet ↗	`LED_0603_1608Metric`
`D8`	GREEN	GPA7 indicator LED	`APT1608SGC` Kingbright Datasheet ↗	`LED_0603_1608Metric`
`J1`	PMOD PLUG 2x6	PMOD peripheral plug (Digilent spec 1.2)	not selected generic	`PinHeader_2x06_P2.54mm_Horizontal`
`JP1`	SDA PULL-UP	Cut to remove the SDA pull-up when chaining modules	—	`SolderJumper-2_P1.3mm_Bridged_RoundedPad1.0x1.5mm`
`JP2`	SCL PULL-UP	Cut to remove the SCL pull-up when chaining modules	—	`SolderJumper-2_P1.3mm_Bridged_RoundedPad1.0x1.5mm`
`JP3`	ADDR 0x20/0x21	I2C address: 1-2 A0 low 0x20 (default), 2-3 A0 high 0x21 (A1/A2 fixed low)	—	`SolderJumper-3_P1.3mm_Bridged12_RoundedPad1.0x1.5mm`
`R1`	330R	Ballast for the GPA0 LED (~5 mA at 3.3 V)	`RC0603FR-07330RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R2`	330R	Ballast for the GPA1 LED (~5 mA at 3.3 V)	`RC0603FR-07330RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R3`	330R	Ballast for the GPA2 LED (~5 mA at 3.3 V)	`RC0603FR-07330RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R4`	330R	Ballast for the GPA3 LED (~5 mA at 3.3 V)	`RC0603FR-07330RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R5`	330R	Ballast for the GPA4 LED (~5 mA at 3.3 V)	`RC0603FR-07330RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R6`	330R	Ballast for the GPA5 LED (~5 mA at 3.3 V)	`RC0603FR-07330RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R7`	330R	Ballast for the GPA6 LED (~5 mA at 3.3 V)	`RC0603FR-07330RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R8`	330R	Ballast for the GPA7 LED (~5 mA at 3.3 V)	`RC0603FR-07330RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R9`	4.7k	I2C SDA pull-up	`RC0603FR-074K7L` Yageo Datasheet ↗	`R_0603_1608Metric`
`R10`	4.7k	I2C SCL pull-up	`RC0603FR-074K7L` Yageo Datasheet ↗	`R_0603_1608Metric`
`R11`	10k	INTA pull-up (configure IOCON open-drain; line rule for open-drain outputs)	`RC0603FR-0710KL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R12`	100R	Series protection on the module-driven INTA line	`RC0603FR-07100RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R13`	10k	INTB pull-up	`RC0603FR-0710KL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R14`	100R	Series protection on the module-driven INTB line	`RC0603FR-07100RL` Yageo Datasheet ↗	`R_0603_1608Metric`
`R15`	10k	~RESET pull-up: expander always out of reset (no host reset line)	`RC0603FR-0710KL` Yageo Datasheet ↗	`R_0603_1608Metric`
`SW1`	SKQG 5.2mm	GPB0 tactile button (active low, internal pull-up)	`SKQGABE010` Alps Alpine Datasheet ↗	`SW_SPST_SKQG_WithoutStem`
`SW2`	SKQG 5.2mm	GPB1 tactile button (active low, internal pull-up)	`SKQGABE010` Alps Alpine Datasheet ↗	`SW_SPST_SKQG_WithoutStem`
`SW3`	SKQG 5.2mm	GPB2 tactile button (active low, internal pull-up)	`SKQGABE010` Alps Alpine Datasheet ↗	`SW_SPST_SKQG_WithoutStem`
`SW4`	SKQG 5.2mm	GPB3 tactile button (active low, internal pull-up)	`SKQGABE010` Alps Alpine Datasheet ↗	`SW_SPST_SKQG_WithoutStem`
`SW5`	SKQG 5.2mm	GPB4 tactile button (active low, internal pull-up)	`SKQGABE010` Alps Alpine Datasheet ↗	`SW_SPST_SKQG_WithoutStem`
`SW6`	SKQG 5.2mm	GPB5 tactile button (active low, internal pull-up)	`SKQGABE010` Alps Alpine Datasheet ↗	`SW_SPST_SKQG_WithoutStem`
`SW7`	SKQG 5.2mm	GPB6 tactile button (active low, internal pull-up)	`SKQGABE010` Alps Alpine Datasheet ↗	`SW_SPST_SKQG_WithoutStem`
`SW8`	SKQG 5.2mm	GPB7 tactile button (active low, internal pull-up)	`SKQGABE010` Alps Alpine Datasheet ↗	`SW_SPST_SKQG_WithoutStem`
`U1`	MCP23017-E/SS	16-bit I2C GPIO expander with interrupts, SSOP-28	`MCP23017-E/SS` Microchip Datasheet ↗	`SSOP-28_5.3x10.2mm_P0.65mm`

Signals#

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

3V3 ADDR0 EXP_INTA EXP_INTB GND GPA0 GPA1 GPA2 GPA3 GPA4 GPA5 GPA6 GPA7 GPB0 GPB1 GPB2 GPB3 GPB4 GPB5 GPB6 GPB7 INTA INTB LED0_A LED1_A LED2_A LED3_A LED4_A LED5_A LED6_A LED7_A RESET_N SCL SCL_PU SDA SDA_PU

Production status#

Schematic ERC	0 violations
PCB layout	not started
DRC	not run
Fab package	not exported
Fabricated	no — design stage only

Source: boards/lab-modules/axl-009-gpio-expander

Catalog #9 in the AruviX lab line (../README.md), level L3. The I2C register-map lesson with instantly visible results — and pin multiplication for big projects (16 IO for 2 PMOD data pins).

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

What it teaches#

The canonical register-map pattern: IODIR (direction), GPPU (internal ~100 kΩ pull-ups), GPIO (read), OLAT (write) — twice, once per port. Write IODIRA=0x00, walk OLATA, watch the LED bar; write GPPUB=0xFF, read GPIOB, see buttons active-low with no external resistors (the internal-pull-up lesson). Then IOCON/INTCON/GPINTEN for interrupt-on-change out of INTA/INTB.

Design#

MCP23017-E/SS (Interface_Expansion:MCP23017x-x-SS, SSOP-28 stock footprint).
GPA0–7 → 330 Ω → green LED (0603, APT1608SGC) → GND: ~5 mA each.
GPB0–7 → tactile button (Alps SKQGABE010, proven MPN) directly to GND; the chip's internal pull-ups replace external resistors (enable GPPUB — documented on the schematic).
INTA → PMOD 1, INTB → PMOD 2, each with 10 kΩ pull-up + 100 Ω series: configure IOCON for open-drain (or active-low push-pull); the pull-up satisfies the line's open-drain rule either way.
I2C on PMOD 3/4 (repeat 9/10), standard 4.7 kΩ pull-ups behind JP1/JP2.
Address: A0 on solder jumper JP3 (GND/VDD → 0x20/0x21 default 0x20), A1/A2 tied to GND.
~RESET: 10 kΩ pull-up only (no host reset line).

PMOD pin	1	2	3	4	5	6	7	8	9	10	11	12
Net	INTA	INTB	SCL	SDA	GND	3V3	NC	NC	SCL	SDA	GND	3V3

Regenerate#

python3 generate_design.py

Remaining for release#

[ ] PCB layout (LED bar and button row on the outline edges), DRC, fab
[ ] hdl/: I2C master + register-map lab, testbench
[ ] BOM export and availability check, design-review checklist