3.3 Universal Serial Bus
The Thunderboard EFM32GG12 board is equipped with a USB Micro-B connector interfacing the EFM32GG12's USB peripheral. The
figure below shows how the USB lines are connected to the MCU. USB_D+ and USB_D- connects to USB_DP and USB_DM, respec-
tively. In addition, 5 V from VBUS is connected to the USB_VREGI and USB_VBUS pins. These provide power to the EFM32GG12's
internal LDO regulator which again powers the USB PHY inside the chip. The output of the LDO is output on the USB_VREGO pin.
When the power selector switch is set in the "MCU USB" position, USB_VREGO is connected to the VMCU net which powers the chip
and all the peripherals in the target voltage domain. For more information, see Section
3.2 Power Supply
.
VBUS
USB_D+
USB_D-
EFM32
USB_VBUS
USB_VREGI
PF10 (USB_DM)
PF11 (USB_DP)
USB Micro-B
Connector
USB_VREGO
Power selector switch
DBG
USB
MCU
USB
Figure 3.4. Universal Serial Bus
3.4 Push Buttons and RGB LEDs
The kit has two user push buttons marked BTN0 and BTN1. They are connected directly to the EFM32GG12 and are debounced by RC
filters with a time constant of 1 ms. The buttons are connected to pins PD5 and PD8.
The kit also features two RGB LEDs marked LED0 and LED1, that are controlled by GPIO pins on the EFM32GG12. The LEDs are
connected in an active-low configuration, and each color can be PWM controlled using the EFM32GG12's TIMER/WTIMER peripherals
to generate a wide variety of colors.
1B
PA12 (TIM2_CC0 #1)
PD6 (TIM1_CC0 #4)
PF12 (TIM1_CC3 #5)
PD5 (GPIO)
PD8 (GPIO)
EFM32
User Buttons
& RGB LEDs
PA13 (TIM2_CC1 #1)
PA14 (TIM2_CC2 #1)
PE12 (TIM1_CC2 #1)
1G
1R
0B
0R
0G
Figure 3.5. Buttons and LEDs
UG371: Thunderboard EFM32GG12 User's Guide
Hardware
silabs.com
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