6.9 Push-buttons
Two buttons are available on the Discovery kit.
RESET button (B1)
The black button connected to NRST is used to reset the STM32 microcontroller. When the button is pressed the
logic state is LOW, otherwise, the logic state is HIGH.
Joystick (B2)
This joystick is a 5-way rock switch using a single ADC input pin PC2. Push-in Select can be used as a digital
user button and EXTI wake-up interrupt.
The joystick position for the ADC value refers to Table 9.
Table 9. Joystick position for the ADC value
Joystick
position
Measurement ratio ADC value (V)
Select 0 0
Left 0.20 0.67
Down 0.40 1.32
Up 0.61 2.01
Right 0.80 2.65
No key pressed 1.0 3.3
VREF is connected to the joystick resistor network as the power supply. So, the joystick can work whenever 3.3 or
1.8 V for the ADC measurement ratio.
UM3292
Hardware layout and configuration
UM3292 - Rev 1
page 16/33
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