The extension headers are given names EXTn where n ϵ [1…7], n is determined by which ID pin is connected to the embedded debugger. A header with ID7 signal from the embedded debugger connected should be called EXT7. PWR, EXT1, EXT2 and EXT3 are standard extension headers that have a predfined position according to the list below:
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PWR is right angled at the top right hand side of the board. This header must always be implemented.
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EXT1 is right angled at the top right hand side of the board, located below the PWR header. This header must always be present.
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EXT2 is right angled and at the bottom right hand side of the board. This header is mandatory for medium and large boards and should not be implemented on small boards.
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EXT3 is right angled pointing downwards
All MCU boards have to implement at least PWR, EXT1, EXT2 (on medium and large boards), and EXT3. EXT4 to EXT7 can be placed differently depending on the board design. EXT4 to EXT7 can either be standard extension headers or application specific headers.
