3.1.1.3 EDBG DGI (Data Gateway Interface)

This is the default serial interface that is used for the Atmel Data Protocol (ADP), which can transport a lot of different data like measurement values, printf style text messages, or other application information. This interface can be based on several different hardware implementations, such as (highest priority first):

• Synchronous UART (target is the master and generates the clock)

• SPI (target is master)

• UART

• I²C

• GPIO

  • Signal a change of power save mode of the target

  • Code profiling by either counting e.g. function calls or by measuring execution time of a code sequence

  • General purpose trigger for a user application

A resistor should be placed between the EDBG and the target on each GPIO line to limit the current that can flow when the user drives the signal from both sides. The resistor value must be selected according to the maximum allowed drive/sink currents on EDBG and target. On the EDBG a typical pad can source/sink around 20mA (at 25°C and 3.3V). The recommended resistor value is 330Ω, which reduces the current to 10mA. In practice it will be less due to resistance within the drivers in EDBG and target.

It is mandatory to implement at least one of the interfaces on an Xplained Pro MCU board and I²C should always be implemented because it can be used to get board information from the EDBG like currently connected extensions.