How to use the SPI ports

This article illustrates how to use the SPI ports on Acme Systems Road Runner SOM based on Microchip SAMA5D27 MPU

Pinout of SPI ports

The SPI bus lines are located on the following pins:

| Signal     | Per A | Per B | Per C | Per D | Per E | Per F 
|------------|-------|-------|-------|-------|-------|-------
| SPI0 MOSI  | PA15  |       | PB0   |       |       |       
| SPI0 MISO  | PA16  |       | PA31  |       |       |       
| SPI0 SCLK  | PA14  |       | PB1   |       |       |       
| SPI0 CS0   | PA17  |       | PA30  |       |       |      
| SPI0 CS1   | PA18  |       | PA29  |       |       |      
| SPI0 CS2   | PA19  |       | PA27  |       |       |      
| SPI0 CS3   | PA20  |       | PA28  |       |       |       
!------------|-------|-------|-------|-------|-------|-------
| SPI1 MOSI  | PD26  |       |       | PC2   | PA23  |       
| SPI1 MISO  | PD27  |       |       | PC3   | PA24  |       
| SPI1 SCLK  | PD25  |       |       | PC1   | PA25  |       
| SPI1 CS0   | PD28  |       |       | PC4   | PA22  |       
| SPI1 CS1   | PD29  |       |       | PC5   | PA26  |       
| SPI1 CS2   | PD30  |       |       | PC6   | PA27  |       
| SPI1 CS3   |       |       |       | PC7   | PA28  |       
|------------|-------|-------|-------|-------|-------|-------

Roadrunner pinout

Kernel configuration

Device Drivers  --->
  [*] SPI support  ---> 
    <*>   Atmel SPI Controller 
    <*>   User mode SPI device driver support

Device tree

/****************/      
/* Enable SPI 0 */
/****************/      

spi0: spi@f8000000 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_spi0_default>;
    status = "okay";

    spidev@0 {
       compatible = "linux,spidev";
       spi-max-frequency = <10000000>;
       reg = <0>;
    };
};

/* Pin definition Peripheral A */

pinctrl_spi0_default: spi0_default {
    pinmux = <PIN_PA14__SPI0_SPCK>,
            <PIN_PA15__SPI0_MOSI>,
            <PIN_PA16__SPI0_MISO>,
            <PIN_PA17__SPI0_NPCS0>,
            <PIN_PA18__SPI0_NPCS1>,
            <PIN_PA19__SPI0_NPCS2>,
            <PIN_PA20__SPI0_NPCS3>;
    bias-disable;
};

/****************/      
/* Enable SPI 1 */
/****************/      

spi1: spi@fc000000 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_spi1_default>;
    status = "okay";

    spidev@0 {
       compatible = "linux,spidev";
       spi-max-frequency = <10000000>;
       reg = <0>;
    };

};

/* Pin definition Peripheral D */

pinctrl_spi1_default: spi1_default {
    pinmux = <PIN_PC1__SPI1_SPCK>,
    <PIN_PC2__SPI1_MOSI>,
    <PIN_PC3__SPI1_MISO>,
    <PIN_PC4__SPI1_NPCS0>;
    bias-disable;
};

Links

Sergio Tanzilli
Systems designer, webmaster of www.acmesystems.it and founder of Acme Systems srl

Personal email: tanzilli@acmesystems.it
Web pages: https://www.acmesystems.it --- https://www.acmestudio.it
Github repositories: https://github.com/tanzilli --- https://github.com/acmesystems
Telegram group dedicated to the Acme Systems boards: https://t.me/acmesystemssrl

Roadrunner technical documentation