March 2012

Doc ID 022625 Rev 1

1/23

UM1502

User manual

STEVAL-MKI111V1 - water level detection

based on the LPS001WP MEMS pressure sensor

Introduction

The STEVAL-MKI111V1 is a low cost demonstration board for the home appliance market.

It is designed to efficiently replace the mechanical or electromechanical pressure sensor in

domestic and industrial washing machines (or similar appliances), where the measurement

of the water level is performed by a pressure measurement.

The system features a 20-pin, 8-bit STM8S103F2 microcontroller running at 16 MHz (RC

user-trimmable internal RC clock), featuring 4 kB of Flash memory, a 10-bit A-D converter,

8/16-bit timers, communication interfaces and 640-byte EEPROM.

The power supply circuitry is based on the LD1117S33, an adjustable and fixed low drop

positive voltage regulator. The power supply provides an output voltage of 3.3 V from an

input voltage in the range 5 V - 12 V DC.

The STEVAL-MKI111V1 is designed to measure temperature and pressure inside

a container (i.e. the drum of a washing machine, or similar), by means of a rubber tube

connected between the container and the demonstration board itself. The core device is the

LPS001WP MEMS pressure sensor, a 300-1100 mbar absolute digital output barometer.

The MEMS communicates with the MCU through an I²C bus.

The demonstration board also features an LED user interface and a connector for an

STMicroelectronics™ debugging tool.

Figure 1.

STEVAL-MKI111V1

www.st.com