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Manage the special GPIO lines

This article explais how to use as normal IO lines some special GPIOs

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 or force the SAMA5D27 CPU to set them as normal GPIO.

In this last case use the Dougg Gilbert GPIO utilities 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):

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:

Related products

RoadRunner D2

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  • CPU Microchip SAMA5D27
  • Cortex A5 @ 500 MHz
  • Very low power consumption:
    396mW in full speed mode
    198mW at Linux prompt
    17mW in standby mode
    10mW in suspend to RAM mode
  • Armhf architecture
  • DDR3L RAM 256 MB
  • QuadSPI 0/16/64/128MB
  • Size: 40x30 mm
  • Plug-in module
  • 200 pins 0.4 mm pitch
  • TFT parallel interface
  • Boot from internal Quad SPI or external uSD/eMMC
  • Linux Kernel 5.15 LTS
  • Debian, Buildroot and Yocto
  • Open source drivers

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  • Al the circuitries you need to test the RoadRunner SoM
  • USB host, USB device, Ethernet port, MicroSD socket
  • Test points for power consumption measurements
  • All the Roadrunner signals exposed on 2.54mm pitch pins
  • On-board supercap for RTC and backup memory circuit

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