UM2032 datasheet(28/48 Pages) STMICROELECTRONICS

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Hardware layout and configuration

UM2032

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DocID029078 Rev 2

6.17.3

Backlight

LEDK and LEDA signals of the LCD module are the cathode and the anode respectively of

the backlight LEDs.

The backlight requires a current source of typically 15 mA capable to deliver a voltage up to

10 V. This function is handled by the backlight-driver circuit STLD40DPUR that is a

switching-mode-boost converter, supplied by the +5 V rail of the discovery kit.

The high level on the signal LCD_BLCTRL (PF5) lights the backlight on. It is possible to dim

the backlight intensity by applying a low-frequency PWM signal to LCD_BLCTRL (1 to

10 kHz).

6.17.4

Touch panel

The touch panel is a capacitive touch panel using an I2C interface. The 10-pin connector

CN14 of the touch panel is located at the bottom side of the discovery kit (see Figure 5:

32F412GDISCOVERY bottom layout). The I2C SDA line is connected to PB7 and the I2C

SCL line is connected to PB6. An interrupt output CTP_INT is connected to port PG5 to be

used as an interruption input of the microcontroller. Port PF12 is the reset of the capacitive

touch panel.

6.18

Joystick and LEDs

The blue button B2 is a 4-direction joystick with a selection mode when pressed in the

center. The logic state is high when one of the five-position switches (Left, Right, Up, Down,

Selection) is pressed. The center position is connected to a wake-up pin of the

microcontroller PA0. This offers the possibility to wake-up the microcontroller by pressing

the center of the joystick.

Four LEDs located near the Arduino Uno V3 connectors CN1 and CN2 are available for the

user (refer to the Figure 4: 32F412GDISCOVERY top layout). From left to right the user

finds LD1, LD2, LD3 and LD4 with their colors green, orange, red and blue respectively. To

light a LED a low-logic state 0 must be written in the corresponding GPIO.

Table 10 gives the assignment of control ports to the LED indicators.

+3.3V

VDD

LCD_TE

LCD_RESET

D10

D11

D12

D13

D14

D15

Table 9. Pin assignment for connector CN7 (continued)

CN7 odd pins

Signal name

CN7 even pins

Signal name

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