MPR084

Sensors

Freescale Semiconductor

5

Preliminary

The remaining 5 connections are SCL, SDA, IRQ, ATTN, and SOUNDER. Depending on the specific application, each of these

control lines can be used by connecting them to a host system. In the most minimal system, the SCL and SDA must be connected

in Figure 4.

Figure 4. Recommended System Connections Schematic

Note that in this configuration the AD0 address line is tied high thus the slave address of the MPR084 0x5D. Alternatively the

address line can be pulled low if the host system needs the MPR084 to be on address 0x5C. This functionality can also be used

to incorporate two MPR084 devices in the same system.

2.3

Serial Interface

Sensor Controller are detailed in the following sections.

2.3.1

Serial-Addressing

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 MPR084, and generates the SCL clock that synchronizes

the data transfer.

The MPR084 SDA line operates as both an input and an open-drain output. A pull-up resistor, typically 4.7k

Ω, is required on SDA.

The MPR084 SCL line operates only as an input. A pull-up resistor, typically 4.7k

Ω, 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 (Figure 5) sent by a master, followed by the MPR084’s 7-bit slave address plus

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

Figure 5. Wire Serial Interface Timing Details

E1

E2

E3

E4

E5

E6

E7

E8

VDD

VSS

SCL

SDA

AD0

SOUNDER

ATTN

IRQ

1

4

3

2

5

8

7

6

16

13

14

15

12

9

10

11

780k

Ω

1

4

3

2

5

8

7

6

E1

E2

E3

E4

E5

E6

E7

E8

GND

MPR084

SCL

SDA

SOUNDER

ATTN

IRQ

8-TOUCH

PAD

ELECTRODE

ARRAY

780k

Ω 780kΩ 780kΩ 780kΩ

780k

Ω 780kΩ 780kΩ

GND

1µF

4.7k

Ω

VDD

VDD

VDD

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