3.4.7 External Memory
The xG24 Dev Kit includes a 32 Mbit Macronix SPI Flash that is connected directly to the EFR32MG24. The MX25R series are ultra-low
power serial flash devices, so there is no need for a separate enable switch to keep current consumption down. However, it is important
that the flash is always put in deep power down mode when not used. This is done by issuing a command over the SPI interface. In
deep power down, the MX25R typically adds approximately 7 nA to the current consumption. The figure below shows how the serial
flash is connected to the EFR32MG24.
EFR32MG24
Serial Flash
32 Mbit
MX25R
SPI_COPI
SPI_CIPO
FLASH_SPI_CS
VMCU
SPI_SCLK
PC01
PC03
PC02
PC00
Figure 3.11. Serial Flash
3.4.8 Push Buttons and RGB LED
The kit has two user push buttons marked BTN0 and BTN1. They are connected directly to the EFR32MG24 and are debounced by RC
filters with a time constant of 1 ms. The buttons are connected to pins PB02 and PB03.
The kit also features an RGB LED marked LED0, controlled by GPIO pins on the EFR32MG24. The LED is connected in an active-low
configuration, and each color can be PWM controlled using the EFR32MG24's TIMER peripherals to generate a wide variety of colors.
User Buttons
& RGB LED
EFR32MG24
LEDR
LEDG
BUTTON1
BUTTON0
PB02
PB03 (EM4WU4)
PD02
PA04
PB00
LEDB
Figure 3.12. Buttons and RGB LED
3.4.9 Precise ADC Voltage Reference
The xG24 Dev Kit includes a high precision voltage reference based on the ADR1581, which features an initial accuracy of 0.12 % (1
mV) and low temperature drift. The voltage reference, when enabled, provides a low-noise 1.25 V external reference input to the
EFR32MG24 IADC, enabling optimal measurement performance.
On the xG24 Dev Kit, the voltage reference is connected through a switch. The switch must therefore be enabled by setting PA00 high
before it can be used by the IADC. The application code should always drive the PA00 signal either high or low to prevent it from float-
ing. The figure below shows how the voltage reference is connected to the EFR32MG24.
VMCU
ADC_VREF
EFR32MG24
VREFP
PA00
V_ADC
ADC_VREF_ENABLE
0: Reference is not enabled
1: Reference is enabled
ADR1581
Voltage
Reference
Figure 3.13. Precise ADC Voltage Reference
UG524: xG24 Dev Kit User's Guide
Hardware
silabs.com
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