This document is a hardware and software guide for the STMPE1801 Xpander Logic™ 18-bit enhanced port expander with keypad controller. The product is a GPIO (general purpose input/output) port expander that can interface with a main digital ASIC via a two-line bidirectional bus (I2C). It offers the flexibility to be configured into a 10x8 matrix keypad controller for QWERTY keyboards and general purpose inputs/outputs. This document provides guidelines and information complementary to the STMPE1801 datasheet, which is necessary for the successful design of STMPE1801 in applications. The first part of the document highlights information on the hardware including external components/connectivity, power, etc. The second part of the document focuses on information regarding the software, in which programming sample codes are shown.
The document serves as a comprehensive guide for designing applications using the STMPE1801 Xpander Logic device. It details hardware configuration requirements such as external components, power sequencing, GPIO output modes (push-pull and open drain), and keypad controller settings for matrix and dedicated keys.
The second part of the note focuses on software implementation, offering a programming guide that covers I2C initialization, interrupt handling, keypad press/release detection, combination key logic, ghost key mitigation strategies, and power mode transitions.
| Interface Bus | two-line bidirectional bus (I2C) |
|---|---|
| Matrix Keys Capacity | Up to 10x8 (80) matrix keys |
| Special Function Keys | Up to 8 special function keys |
| Dedicated Keys | Up to 4 dedicated keys |
The device provides push-pull type outputs by default, but open drain outputs can be configured via software programming.
A 10 kΩ pull-up resistor is recommended at the RSTB pin.