Freescale Semiconductor Evaluation Board MPR031/2 for 2- or 3-pad touch sensor controllers DEMOMPR031 DEMOMPR031 データシート

Sensors

4

Freescale Semiconductor

The MPR03X uses an I

2

C Serial Interface. The I

2

C protocol implementation and the specifics of communicating with the Touch 

Sensor Controller are detailed in the following sections.

The MPR03X operates as a slave that sends and receives data through an I

2

C 2-wire interface. The interface uses a Serial Data 

Line (SDA) and a Serial Clock Line (SCL) to achieve bi-directional communication between master(s) and slave(s). A master 
(typically a microcontroller) initiates all data transfers to and from the MPR03X, and it generates the SCL clock that synchronizes 
the data transfer.

The MPR03X SDA line operates as both an input and an open-drain output. A pull-up resistor, typically 4.7k

, is required on 

SDA. The MPR03X SCL line operates only as an input. A pull-up resistor, typically 4.7k

, is required on SCL if there are multiple 

masters on the 2-wire interface, or if the master in a single-master system has an open-drain SCL output.

Each transmission consists of a START condition (

) sent by a master, followed by the MPR03X’s 7-bit slave address plus 

R/W bit, a register address byte, one or more data bytes, and finally a STOP condition. 

Both SCL and SDA remain high when the interface is not busy. A master signals the beginning of a transmission with a 
START (S) condition by transitioning SDA from high to low while SCL is high. When the master has finished communicating with 
the slave, it issues a STOP (P) condition by transitioning SDA from low to high while SCL is high. The bus is then free for another 
transmission. 

SCL

SDA

tLOW

tHIGH

tF

tR

tHD STA

tHD DAT

tHD STA

tSU DAT

tSU STA

tBUF

tSU STO

START

CONDITION

STOP

CONDITION

REPEATED START

CONDITION

START

CONDITION

DATA LINE STABLE

DATA VALID

CHANGE OF

DATA ALLOWED

SDA

SCL