> For the complete documentation index, see [llms.txt](https://docs.echook.uk/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.echook.uk/circuit-schematics/expansion-port.md).

# Expansion Port

![](https://1289908854-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LChAPz4ZYgbOhdQ_bOF%2F-LChAQceEbyRROlhC11i%2F-LChAWFXnP524SQZzKnM%2Fexpansion-port-schematic.png?generation=1526545127112761\&alt=media)

This is not a circuit block, but it is the connection point for expanding the eChook board. It exposes Arduino pins that are unused by default: 6 digital I/O pins and 2 analogue input pins. Note that A1 can be used for digital I/O, but due to internal Arduino wiring, A6 is *only* an analogue input.

On the PCB, the expansion port pads are counted anticlockwise from the square pad: pins 1-7 down one side, then 8-14 back up the other.