Using all the 10 serial ports of RoadRunner

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 article has been tried with a Linux Kernel 4.19.134 and a Debian Buster 10 distribution.

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

acme-roadrunner-10uart.dts

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