Bosch XDK110 Getting Started page 5

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Extension Bus Advanced Guide | XDK110
Additionally, please note that the pins of the extension bus are protected against electrostatic discharge (ESD) up to 4 kV.
This includes a serial resistance of 40 Ohm into the signal path. Please note that this is no problem for communication, but
it need to be considered when powering external components via GPIO, e.g. an LED.
Keep those limitations of the Extension Bus gateway in mind when interacting with the UART, SPI and I2C pins. For further
information about the general characteristics and limitations, please refer to the basic Extension Bus guide.
Before you start to 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 work on a
different voltage level, a level shifter has to be used to ensure communication with the MCU.
Failing to do so can lead to permanent damage of the XDK!
The micro controller supports four general purpose pin current drive strength settings: 0.5, 2,6 and 20 mA. The default
drive strength is set to 6 mA and an alternative level can be defined for each port. For how to configure these current drive
strengths, please refer to chapter 1.X in the Extension Bus Basis guide. While each pin can receive or provide maximum
20 mA current, there is a limit on the maximum combined current sourced or sank by all GPIOs.
As the XDK board itself has many useful peripherals connected to the MCU, which may require specific alternative drive
strength settings if enabled, it is recommended to use the default 6 mA drive strength for all I/O pins of the extension board
connector and to limit the total amount of current sourced or sank through the extension board bus to 50 mA. Exceeding
these limits might permanently damage the micro controller!