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Using up to 10 serial ports on RoadRunner SOM

On the Roadrunner is possible to use up to 9 serial ports for user purposes plus the debug serial port. This article illustrates how to activate at the same time all the ports available.

This is pheriperals available to implements the serial ports. When more IOset are listed the peripheral lines can be moved on another set of pins to avoid conflicts with other peripherals.

  • UART0 (IOset1)
  • UART1 (IOset1 or IOset2) (Used by default as debug port)
  • UART2 (IOset1 or IOset2 or IOset3)
  • UART3 (IOset1 or IOset3)
  • UART4 (IOset1)
  • FLEXCOM0 (IOset1)
  • FLEXCOM1 (IOset1)
  • FLEXCOM2 (IOset1 or IOset2)
  • FLEXCOM3 (IOset1 or IOset2)
  • FLEXCOM4 (IOset1)

To assign the /dev/ttySx device to each port use this alias list at the beginning of device tree file:

aliases {
    serial0 = &uart1; /* /dev/ttyS0 Debug port */
    serial1 = &uart2; /* /dev/ttyS1            */
    serial2 = &uart3; /* /dev/ttyS2            */
    serial3 = &uart4; /* /dev/ttyS3            */
    serial4 = &uart0; /* /dev/ttyS4            */
    serial5 = &uart5; /* /dev/ttyS5            */
    serial6 = &uart6; /* /dev/ttyS6            */
    serial7 = &uart7; /* /dev/ttyS7            */
    serial8 = &uart8; /* /dev/ttyS8            */
    serial9 = &uart9; /* /dev/ttyS9            */
};

UART0

Signal Dir Description IOSet1
URXD0 I Receive data PB26
UTXD0 O Transmit data PB27 
uart0: serial@f801c000 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_uart0_ioset1>;
    status = "okay";
};

pinctrl@fc038000 {
    pinctrl_uart0_ioset1: uart0_ioset1 {
        pinmux = <PIN_PB26__URXD0>,
             <PIN_PB27__UTXD0>;
        bias-disable;
    };
};

UART1 (Debug port)

Signal Dir Description IOSet1
URXD1 I Receive data PD3
UTXD1 O Transmit data PD2 
uart1: serial@f8020000 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_uart1_ioset1>;
    atmel,use-dma-rx;
    atmel,use-dma-tx;
    status = "okay";
};

pinctrl@fc038000 {
    pinctrl_uart1_ioset1: uart1_ioset1 {
        pinmux = <PIN_PD2__URXD1>,
             <PIN_PD3__UTXD1>;
        bias-disable;
    };
};

UART2

Signal Dir Description IOSet1
URXD2 I Receive data PD4
UTXD2 O Transmit data PD5
Signal Dir Description IOSet2
URXD2 I Receive data PD23
UTXD2 O Transmit data PD24
Signal Dir Description IOSet3
URXD2 I Receive data PD19
UTXD2 O Transmit data PD20 
uart2: serial@f8024000 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_uart2_ioset1>;
    atmel,use-dma-rx;
    atmel,use-dma-tx;
    status = "okay";
};


pinctrl@fc038000 {
    pinctrl_uart2_ioset1: uart2_ioset1 {
        pinmux = <PIN_PD4__URXD2>,
             <PIN_PD5__UTXD2>;
        bias-disable;
    };

    pinctrl_uart2_ioset2: uart2_ioset2 {
        pinmux = <PIN_PD23__URXD2>,
             <PIN_PD24__UTXD2>;
        bias-disable;
    };

    pinctrl_uart2_ioset3: uart2_ioset3 {
        pinmux = <PIN_PD19__URXD2>,
             <PIN_PD20__UTXD2>;
        bias-disable;
    };
};

UART3

Signal Dir Description IOSet1
URXD3 I Receive data PC12
UTXD3 O Transmit data PC13
Signal Dir Description IOSet2
URXD3 I Receive data PC31
UTXD3 O Transmit data PD0
Signal Dir Description IOSet3
URXD3 I Receive data PB11
UTXD3 O Transmit data PB12 
uart3: serial@fc008000 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_uart3_ioset1>;
    atmel,use-dma-rx;
    atmel,use-dma-tx;
    status = "okay";
};


pinctrl@fc038000 {
    pinctrl_uart3_ioset1: uart3_ioset1 {
        pinmux = <PIN_PC12__URXD3>,
             <PIN_PC13__UTXD3>;
        bias-disable;
    };

    pinctrl_uart3_ioset2: uart3_ioset2 {
        pinmux = <PIN_PC31__URXD3>,
             <PIN_PD0__UTXD3>;
        bias-disable;
    };

    pinctrl_uart3_ioset3: uart2_ioset3 {
        pinmux = <PIN_PB11__URXD3>,
             <PIN_PB12__UTXD3>;
        bias-disable;
    };
};

UART4

Signal Dir Description IOSet1
URXD4 I Receive data PB3
UTXD4 O Transmit data PB4 
uart4: serial@fc00C000 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_uart4_ioset1>;
    status = "okay";
};


pinctrl@fc038000 {
    pinctrl_uart4_ioset1: uart4_ioset1 {
        pinmux = <PIN_PB3__URXD4>,
             <PIN_PB4__UTXD4>;
        bias-disable;
    };
};

FLEXCOM0

Signal Dir Description IOSet1
FLEXCOM0_IO1 I Receive data PB28
FLEXCOM0_IO0 O Transmit data PB29 
flx0: flexcom@f8034000 {
    atmel,flexcom-mode = <ATMEL_FLEXCOM_MODE_USART>;
    status = "okay"; 

    uart5: serial@200 {
        compatible = "atmel,at91sam9260-usart";
        reg = <0x200 0x200>;
        interrupts = <19 IRQ_TYPE_LEVEL_HIGH 7>;
        clocks = <&flx0_clk>;
        clock-names = "usart";
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_flx0_ioset1>;
        atmel,fifo-size = <32>;
        status = "okay";
    };
};

TX and RX lines

pinctrl@fc038000 {
    pinctrl_flx0_default: flx0_ioset1 {
        pinmux = <PIN_PB28__FLEXCOM0_IO0>, /* TX */
                 <PIN_PB29__FLEXCOM0_IO1>; /* RX */
        bias-disable;
    };
};

TX and RX lines plus CTS and RTS

pinctrl@fc038000 {
    pinctrl_flx0_default: flx0_ioset1 {
        pinmux = <PIN_PB28__FLEXCOM0_IO0>, /* TX */
                 <PIN_PB29__FLEXCOM0_IO1>, /* RX */
                 <PIN_PB31__FLEXCOM0_IO3>,
                 <PIN_PC0__FLEXCOM0_IO4>;
        bias-disable;
    };
};

FLEXCOM1

Signal Dir Description IOSet1
FLEXCOM1_IO1 I Receive data PA23
FLEXCOM1_IO0 O Transmit data PA24 
flx1: flexcom@f8038000 {
    atmel,flexcom-mode = <ATMEL_FLEXCOM_MODE_USART>;
    status = "okay"; 

    uart6: serial@200 {
        compatible = "atmel,at91sam9260-usart";
        reg = <0x200 0x200>;
        interrupts = <20 IRQ_TYPE_LEVEL_HIGH 7>;
        clocks = <&flx1_clk>;
        clock-names = "usart";
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_flx1_ioset1>;
        atmel,fifo-size = <32>;
        status = "okay";
    };
};

pinctrl@fc038000 {
    pinctrl_flx1_ioset1: flx1_ioset1 {
        pinmux = <PIN_PA24__FLEXCOM1_IO0>,
             <PIN_PA23__FLEXCOM1_IO1>;
        bias-disable;
    };
};

FLEXCOM2

Signal Dir Description IOSet1
FLEXCOM2_IO1 I Receive data PA27
FLEXCOM2_IO0 O Transmit data PA26 
flx2: flexcom@fc010000 {
    atmel,flexcom-mode = <ATMEL_FLEXCOM_MODE_USART>;
    status = "okay";

    uart7: serial@200 {
        compatible = "atmel,at91sam9260-usart";
        reg = <0x200 0x200>;
        interrupts = <21 IRQ_TYPE_LEVEL_HIGH 7>;
        clocks = <&flx2_clk>;
        clock-names = "usart";
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_flx2_ioset1>;
        atmel,fifo-size = <32>;
        status = "okay";
    };
};

pinctrl@fc038000 {
    pinctrl_flx2_ioset1: flx2_ioset1 {
        pinmux = <PIN_PD26__FLEXCOM2_IO0>,
             <PIN_PD27__FLEXCOM2_IO1>;
        bias-disable;
    };
};

FLEXCOM3

Signal Dir Description IOSet1
FLEXCOM3_IO1 I Receive data PA13
FLEXCOM3_IO0 O Transmit data PA15 
flx3: flexcom@fc014000 {
    atmel,flexcom-mode = <ATMEL_FLEXCOM_MODE_USART>;
    status = "okay";

    uart8: serial@200 {
        dmas = <0>, <0>;
        compatible = "atmel,at91sam9260-usart";
        reg = <0x200 0x200>;
        interrupts = <22 IRQ_TYPE_LEVEL_HIGH 7>;
        clocks = <&flx3_clk>;
        clock-names = "usart";
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_flx3_ioset1>;
        atmel,fifo-size = <32>; 
        status = "okay"; 
    };
};

pinctrl@fc038000 {
    pinctrl_flx3_ioset1: flx3_ioset1 {
        pinmux = <PIN_PA15__FLEXCOM3_IO0>,
             <PIN_PA13__FLEXCOM3_IO1>;
        bias-disable;
    };
};

FLEXCOM4

Signal Dir Description IOSet1
FLEXCOM4_IO1 I Receive data PC29
FLEXCOM4_IO0 O Transmit data PC28 
flx4: flexcom@fc018000 {
    atmel,flexcom-mode = <ATMEL_FLEXCOM_MODE_USART>;
    status = "okay";

    uart9: serial@200 {
        compatible = "atmel,at91sam9260-usart";
        reg = <0x200 0x200>;
        interrupts = <23 IRQ_TYPE_LEVEL_HIGH 7>;
        clocks = <&flx4_clk>;
        clock-names = "usart";
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_flx4_ioset1>;
        atmel,fifo-size = <32>;
        status = "okay"; 
    };
};

pinctrl@fc038000 {
    pinctrl_flx4_ioset1: flx4_ioset1 {
        pinmux = <PIN_PC28__FLEXCOM4_IO0>,
             <PIN_PC29__FLEXCOM4_IO1>;
        bias-disable;
    };
};

Check the serial devices

ls -al /dev/ttyS* crw------- 1 root tty 4, 64 Jul 28 10:22 /dev/ttyS0 crw-rw---- 1 root dialout 4, 65 Jul 28 09:10 /dev/ttyS1 crw-rw---- 1 root dialout 4, 66 Jul 28 09:10 /dev/ttyS2 crw-rw---- 1 root dialout 4, 67 Jul 28 09:10 /dev/ttyS3 crw-rw---- 1 root dialout 4, 68 Jul 28 09:10 /dev/ttyS4 crw-rw---- 1 root dialout 4, 69 Jul 28 09:10 /dev/ttyS5 crw-rw---- 1 root dialout 4, 70 Jul 28 09:10 /dev/ttyS6 crw-rw---- 1 root dialout 4, 71 Jul 28 09:10 /dev/ttyS7 crw-rw---- 1 root dialout 4, 72 Jul 28 09:10 /dev/ttyS8 crw-rw---- 1 root dialout 4, 73 Jul 28 09:10 /dev/ttyS9

Install minicon

sudo apt update sudo apt install -y minicom

To use minicom be shure to don't use the Roadrunner debug port from your PC to avoid strange behaviour. Use a ssh remote session instead

Launch and select for example the port /dev/ttyS1

sudo minicom -s

Select:

then set:

wire together the lines PB27 (TXD0) and PB26 (RXD0) to do an hardware loopback the type some characters on minicom to see if it works

Change the limit on /dev/tty entries

To enable more than 8 serial lines change in:

drivers/tty/serial/atmel_serial.c

the line:

#define ATMEL_MAX_UART      8

in:

#define ATMEL_MAX_UART      10

A ready-to-use device tree source

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