XDK Extension Bus

The XDK comes with an interface 26-pin interface for the XDK Gateway. The extension bus allows access to the XDK’s micocontroller unit (MCU) pins and thus attaching external devices such as sensors or actuators to it. All MCU pins are GPIOs and can be configured freely within the limitations of the MCU.

MCU pins on the Extension Bus

The extension bus I/O pins are labelled with the respective MCU pin designator. Since all pins of XDK’s MCU are general purpose pins, alternative functionality can be configured for each pin. For example, if a pin is labelled as a Timer, it can also be configured to be used for a pulse counter, and so on. The different functionalities of these pins are described in the data sheet of the EFM32GG390.

The following table describes the selected functionalities for each pin.

Connector Pin	MCU Pin	Suggested Use	Multiplex Location	Macro
A1	PA0	Timer0 compare	TIMER0 #4	EXTENSION_TIM0_CC0
A2	PC0	Timer0 compare	TIMER0 #4	EXTENSION_TIM0_CC1
A3	PC1	Timer0 compare	TIMER0 #4	EXTENSION_TIM0_CC2
A4	PC2	Timer0 Dead time insertion	TIMER0 #4	EXTENSION_TIM0_CDTI0
A5	PC3	Timer0 Dead time insertion	TIMER0 #4	EXTENSION_TIM0_CDTI1
A6	PC4	Timer0 Dead time insertion	TIMER0 #4	EXTENSION_TIM0_CDTI2
A7	PC8	Timer2 Capture operations	TIMER2 #2	EXTENSION_TIM2_CC0
A8	PC9	Timer2 Capture operations	TIMER2 #2	EXTENSION_TIM2_CC1
A9	PC10	Timer2 Capture operations	TIMER2 #2	EXTENSION_TIM2_CC2
A10	PD6	ADC0 Channel6	n/a	EXTENSION_ADC0_CH6
A11	PD5	ADC0 Channel5	n/a	EXTENSION_ADC0_CH5
A12	PA1	General purpose I/O	n/a	EXTENSION_GPIO_IN_OUT_0
A13	PE2	General purpose I/O	n/a	EXTENSION_GPIO_IN_OUT_1
B1	PB9	UART1 TX	UART1 #2	EXTENSION_UART1_TX
B2	PB10	UART1 RX	UART1 #2	EXTENSION_UART1_RX
B3	PB2	UART1 RTS	n/a	EXTENSION_UART1_RTS
B4	PF6	UART1 CTS	n/a	EXTENSION_UART1_CTS
B5	PB4	SPI MISO	USART2 #1	EXTENSION_US2_MISO
B6	PB3	SPI MOSI	USART2 #1	EXTENSION_US2_MOSI
B7	PB5	SPI Clock	USART2 #1	EXTENSION_US2_SCK
B8	PD8	SPI Chip select	n/a	EXTENSION_US2_CS
B9	PB11	I2C1 data line (pull-up)	I2C1 #1	EXTENSION_I2C1_SDA
B10	PB12	I2C1 clock line (pull-up)	I2C1 #1	EXTENSION_I2C1_SCL
B11	2V5	Power; Limit 100mA continuous/peak	n/a	n/a
B12	3V3	Power; Limit 100mA continuous/peak	n/a	n/a
B13	GND	Power	n/a	n/a

However, due to shared resources with internal components, restrictions apply to the possible configurations of certain extension bus pins through internal modification.

The following pins differ in their electrical behavior due to other components on the signal paths:

• Pins B9 and B10 are equipped with an internal pull-up resistor of 3.32 kOhm and are therefore usable for I2C communication only.

• Pins PD5 and PD6 have anti-alias (low-pass) filters with a cut off frequency of ~400 MHz. These are mainly used as single input ADC pins.

  Additionally, please keep the following general characteristics of the pins on the extension bus in mind:

• The pins of the extension bus are protected against electrostatic discharge (ESD) up to 4 kV. This includes a serial resistance of 40 Ohm on the signal path. While this is no problem for communication, it has to be considered when powering external components via GPIO, e.g. an LED.

• Any pin you intend to use will have to be configured accordingly. Most of the pins are assigned with default modes and values. For more information, please refer to SDK/xdk110/Platform/BSP/ source/BSP_BoardSettings.h and SDK/xdk110/Platform/BSP/source/BSP_BoardExtSettings.h.

• The 2.5 V and 3.3 V power supply pins can provide up to 100 mA supply current. Please note that these limitations apply to the maximal peak current, too. By default, the 3V3 supply pin is in a disabled state. For your application, please use the function Board_EnablePowerSupply3V3(EXTENSION_BOARD) from the interface BSP_BoardShared.h to enable the 3V3 pin on the extension bus.

Before you connect external components to the XDK, please note the following limitations.

The pin voltage of every general purpose extension bus pin is 2.5 V. If you connect external components that operate on a different voltage, a level shifter has to be used to ensure communication with the MCU will work. Failing to do so can cause permanent damage to the MCU!