ST 32F412GDISCOVERY, User Manual

Page: 30 / 40

Hardware layout and configuration UM2032
30/40 UM2032 Rev 3
5.17.3 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 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).
5.17.4 Touch panel
The touch panel is a capacitive touch panel using an I
2
C 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 I
2
C SDA line is connected to PB7 and the I
2
C
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.
5.18 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 12 gives the assignment of control ports to the LED indicators.
9 D2 10 +3.3 V
11 D3 12 VDD
13 LCD_TE 14 LCD_RESET
15 D4 16 D5
17 D6 18 D7
19 D8 20 D9
21 D10 22 D11
23 D12 24 D13
25 D14 26 D15
Table 11. Pin assignment for connector CN7 (continued)
CN7 odd pins Signal name CN7 even pins Signal name