Preliminary
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2010-04-09 - t0005_1.10
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6 Peripherals
The development kit has a rich set of user programmable peripherals that allows most of the EFM32G
on-chip peripherals to be evaluated and tested.
The registers referred to in this chapter are accessible using the kit Board Support Package. Refer to
the BSP chapter in this manual to learn how to enable the motherboard peripherals. A reference to all
the registers and their function is in the Board Controller chapter.
6.1 Pushbuttons
The state of the pushbuttons marked SW1 to SW4 can be read from the board controller, using the
PUSHBUTTON register. The buttons are debounced by RC filters with a time constant of 1ms.
6.2 DIP switches
The dipswitch positions can be read from the board controller, using the DIPSWITCH register. The
switches are not debounced.
6.3 Joystick
The joystick position can be read from the board controller, using the JOYSTICK register. The positions
are debounced by RC filters with a time constant of 1ms.
6.4 LEDs
The user LEDs can be set by the board controller by writing to the LED register. The state of the LEDs
can also be read back.
6.5 Differential analog input
This BNC input signal is converted to a differential signal by a differential operational amplifier using
ground as reference.The op amp output common mode voltage is 1.65V, and also implements a low-
pass active filter with a 3dB cutoff frequency of 4MHz.
The common mode voltage can be changed by adjusting the R5 and R12 resistors. It can also be
controlled by the VCM pin on the EFM if a shunt resistor is soldered in place of R252 and R5 and R12
are removed.
The peripheral is connected directly to the EFM when the ANALOG_DIFF bit in the PERCTRL register
in the board controller has been set.
6.6 Single ended analog inputs
This peripheral connects the two BNCs to the ADC on the EFM, and can be used as a single ended
analog interface. It can also be used for digital I/O.
The peripheral is connected directly to the EFM when the ANALOG_SE bit in the PERCTRL register in
the board controller has been set.
6.7 Line in / Audio in
This is an audio input amplifier with filter, and the output connects to the ADC of the EFM. The gain
of the amplifier is 0 dB and the bias point is 1.65 V. The filter is a 3-pole linear phase MFB filter with
a cutoff frequency of 20 kHz. In addition to the input amplifier and filter, the line in is equipped with a
voltage divider resulting in 6dB attenuation.
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