AN2591

Using a STMPE801 (I²C bus) 8-bit I/O port expander

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Using a STMPE801 (I²C bus) 8-bit I/O port expander

The STMPE801 is a General Purpose Input / Output (GPIO) expander specially designed

for expanding the input/output lines and solving the common problem of not having enough

GPIOs available for the application. This IC offers several features:

●

8 available GPIOs.

●

Each GPIO can be individually configured as input or output in the data direction

register GPDR and can be a source of an external interrupt configurable in the

IEGPIOR register.

●

●

Note:

For more details refer to the STMPE801 datasheet.

3.1

Expanding the number of inputs/outputs to 8 lines

Figure 9 shows how the STMPE801 is connected via I2C bus to the microcontroller. When

= Vcc) the device address will be 0x88.

Figure 9.

Eight channel expander

Each GPIO (0 to 7) can be configured independently as input or output (see details in the

GPDR section in STMPE801 datasheet). You can read the state of each GPIO in the GPMR

register. To set a GPIO state, you need to set its value in the GPSR register.

The INT (interrupt) output can be optionally used to increase the number of external inter-

rupt sources of the microcontroller by connecting it to one of external interrupt lines: XTI

microcontroller interrupt input. To use this option, you must first configure the IEGPIOR reg-

ister to enable the interrupt from a particular GPIO interrupt source to the host. After that,

µC

SDA

STMPE801MTR

SCL

XTI

3

5

4

6

7

8

9

10

VCC

16

VIO

1

3.3v

GND

INT

SCLK

SDAT

GPIOX.Y

RESET

ADDR0

4.7K

4.7K

R1

R2

8 inputs/

outputs

15

GPIO0

GPIO1

GPIO2

GPIO3

GPIO4

GPIO5

GPIO6

GPIO7

13

11

12

14

2

If needed

(I2C device address=0x82)