# Manage the special GPIO lines 

<abstract>
This article explais how to use as normal IO lines some special GPIOs  
</abstract>

## PD14...PD18

This pins are defined by default as JTAG pins. To use them as normal GPIO it is possible
to change the fuse configuration using [SAM-BA](https://www.acmesystems.it/SAM-BA) or force
the SAMA5D27 CPU to set them as normal GPIO.

In this last case use the [Dougg Gilbert GPIO utilities](/roadrunner_gpio_utils) and add these
line at Linux startup:

	# mem2io -w -i fc0380c0,7c000
	# mem2io -w -i fc0380c4,200
	
## PA30

PA30 has by default an internal pull down resistor and is used as SDMMC1_CD
signal.

To use it as normal GPIO use this command ([Dougg Gilbert GPIO utilities](/roadrunner_gpio_utils)):

	mem2io -w -i fc038000,40000000 e mem2io -w -i fc038004,200

## How to set pins as GPIO using the device tree	

To set as normal GPIO some pins inside the device tree
use a section like this adding the pins you need:

	pinctrl_gpio: gpio_default {
	
	    pinmux = <PIN_PA12__GPIO>, 
	            <PIN_PD31__GPIO>,  
	            <PIN_PB22__GPIO>,  
	            <PIN_PC9__GPIO>,   
	            <PIN_PB17__GPIO>,  
	            <PIN_PB16__GPIO>,  
	            <PIN_PD13__GPIO>,  
	            <PIN_PD16__GPIO>,  
	            <PIN_PD18__GPIO>;  
	             
	    bias-pull-down;
	};
	
To compile the device tree follow this article:

* @article='roadrunner_compile_kernel_4_19'
 
@include='adv_roadrunner'