MCP23008

@@ -0,0 +1,64 @@+# MCP23008++**Microchip** · I2C I/O expander · SOIC-18W++Adds eight general-purpose I/O pins to a host over I2C. Each of the eight pins (GP0-GP7) is independently set as input or output, with optional pull-ups and per-pin interrupt-on-change that flags a change on the INT output, so the host is told which pin moved without polling. Three address pins (A0-A2) put up to eight devices on one bus. The 8-bit sibling of the MCP23017, at half the pins.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | SCL | input | I2C serial clock input. Supports Standard-mode (100 kHz), Fast-mode (400 kHz) and High-speed mode (1.7 MHz). Requires an external pull-up resistor to VDD. |+| 2 | SDA | bidirectional | I2C serial data (open-drain, bidirectional). Requires an external pull-up resistor to VDD. |+| 3 | A2 | input | Hardware address input bit 2. Sets the upper I2C slave-address bit of the MCP23008 (base address 0100 A2 A1 A0). Must be biased externally to VDD or VSS. |+| 4 | A1 | input | Hardware address input bit 1. Must be biased externally to VDD or VSS. |+| 5 | A0 | input | Hardware address input bit 0. Must be biased externally to VDD or VSS. |+| 6 | RESET | input | External active-low reset input. Drive low to reset the device; hold high (or tie to VDD) for normal operation. |+| 7 | NC | unconnected | No connect on the MCP23008 (this pin is the SPI chip-select CS on the MCP23S08 variant). Leave floating or tie to VDD/VSS. |+| 8 | INT | output | Interrupt output. Configurable as active-high, active-low, or open-drain via the IOCON register. Asserted on GPIO input change or mismatch vs DEFVAL. |+| 9 | VSS | power_in | Ground reference (0 V). |+| 10 | GP0 | bidirectional | General-purpose bidirectional I/O bit 0. Individually configurable as input or output; supports interrupt-on-change and an internal weak pull-up to VDD. |+| 11 | GP1 | bidirectional | General-purpose bidirectional I/O bit 1. Interrupt-on-change and internal weak pull-up available. |+| 12 | GP2 | bidirectional | General-purpose bidirectional I/O bit 2. Interrupt-on-change and internal weak pull-up available. |+| 13 | GP3 | bidirectional | General-purpose bidirectional I/O bit 3. Interrupt-on-change and internal weak pull-up available. |+| 14 | GP4 | bidirectional | General-purpose bidirectional I/O bit 4. Interrupt-on-change and internal weak pull-up available. |+| 15 | GP5 | bidirectional | General-purpose bidirectional I/O bit 5. Interrupt-on-change and internal weak pull-up available. |+| 16 | GP6 | bidirectional | General-purpose bidirectional I/O bit 6. Interrupt-on-change and internal weak pull-up available. |+| 17 | GP7 | bidirectional | General-purpose bidirectional I/O bit 7. Interrupt-on-change and internal weak pull-up available. |+| 18 | VDD | power_in | Supply voltage. Operating range 1.8 V to 5.5 V (I2C speed derated at lower voltages: 100 kHz min at 1.8 V, 400 kHz at 2.7 V, 1.7 MHz at 4.5 V). Decouple to VSS with a 0.1 µF ceramic near the pin. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | 8-bit I2C I/O expander |+| Interface | I2C (up to 1.7 MHz) |+| I/O | 8 pins (GP0-GP7), input or output |+| Interrupt | INT output, interrupt-on-change per pin |+| Addresses | 8 (A0-A2) |+| Pull-ups | Software-enabled per pin (100 kΩ) |+| Supply | 1.8-5.5 V |+| Package | SOIC-18W (300 mil) |++## Ordering variants++- `MCP23008-E/SO (SOIC-18W)`+- `MCP23008-E/P (PDIP-18)`+- `MCP23008-E/SS (SSOP-20)`+- `MCP23008-E/ML (QFN-20)`++## CAD (KiCad official)++- Symbol: `Interface_Expansion:MCP23008-xSO (KiCad official)`+- Footprint: `Package_SO:SOIC-18W_7.5x11.6mm_P1.27mm`+- 3D model: SOIC-18W (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Microchip datasheet](https://ww1.microchip.com/downloads/en/DeviceDoc/MCP23008-MCP23S08-Data-Sheet-20001919F.pdf) (43 pp, sha256 `3516fba5df6da78c`, retrieved 2026-08-17, tier: manufacturer)+- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.+- **CAD:** KiCad official libraries (CC-BY-SA 4.0).++[Datasheet PDF](docs/mcp23008-datasheet.pdf)

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