# GPIO pins - how do they work

**URL:** <https://forum.clockworkpi.com/t/gpio-pins-how-do-they-work/199>\
**Category:** GameShell\
**Tags:** tinkering\
**Created:** [February 20, 2018, 2:08pm UTC](https://forum.clockworkpi.com/t/gpio-pins-how-do-they-work/199 "2018-02-20T14:08:41Z")\
**Posts on this page:** 1\
**Showing post:** 8

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**Author:** ![guu](https://avatars.discourse-cdn.com/v4/letter/g/7ab992/32.png) [@guu](https://forum.clockworkpi.com/u/guu)\
**Post date:** [February 17, 2019, 7:25am UTC](https://forum.clockworkpi.com/t/gpio-pins-how-do-they-work/199/8 "2019-02-17T07:25:35Z")

</div>

[https://github.com/clockworkpi/GameShellDocs](https://github.com/clockworkpi/GameShellDocs)

`clockwork_Mainboard_Schematic.pdf`

search Debug UART  
 ![debug](https://cdck-file-uploads-canada1.s3.dualstack.ca-central-1.amazonaws.com/flex029/uploads/clockworkpi/original/2X/e/efc8919156426d69e65a7e895d0495cc8cf16e8d.png)

and here is the order in reality  
reference picture

![IMG_20190217_145232R](https://cdck-file-uploads-canada1.s3.dualstack.ca-central-1.amazonaws.com/flex029/uploads/clockworkpi/original/2X/a/a80b7701697832026c9decb253df9dacaacf0e46.jpeg)

from left to right is

blue green yellow white  
1, 2, 3, 4…

in above Mainboard Schematic Layout

so if you want a usb-uart connector, just **leave the blue alone** and connect the  
green(rx) yellow(tx) ,white(GND) and it will be done

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