The MCP23017 pHAT from ModMyPi is the perfect I/O expansion pHAT for your Raspberry Pi Zero. The pHAT features a single removable MCP23017 DIP IC, which utilise two i2c pins (which can be shared with other devices if required), and in exchange gives your Raspberry Pi Zero an additional 16 GPIO ports! Each I/O pin can be configured as an input, output or an input with a pullup resistor. The MCP23017 pHAT is stackable, featuring selectable i2c address jumpers which supports up to 8 independent addresses: This means you can add up to 128 additional I/O's to a single Raspberry Pi by stacking up to 8 MCP23017 pHAT's!
The MCP23017 pHAT can also be used to protect your Raspberry Pi! We've used removable, rather than surface mount, MCP23017 DIP IC's which can act as replaceable buffer for the Raspberry Pi's GPIO, essentially protecting your Raspberry Pi from damage via the GPIO ports. The MCP23017 pHAT is powered via the Raspberry Pi's GPIO port, but features an included (but unsoldered) terminal block for advanced users wanting to use an external 5V source, or stack multiple MCP23017 pHATs on a single Pi. The isolation jumper "PWR JUMPER" must be removed when using an external source.
Good value. Works well. Stackable but supplied hardware not really sutiable for that - needs longer stansoffs with male/female ends, especially if properly constructed 16 pin connectors used.