DESK-MX6UL-L/Peripherals/UART
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| Version | Issue Date | Notes | |
| 1.0.0 | Apr 2021 | First DESK release | |
| 3.0.0 | Feb 2022 | 3.0.0 DESK release | |
Contents
Peripheral UART[edit | edit source]
Device tree configuration[edit | edit source]
Here below an example of device tree configuration used on standard DAVE's kit for the AXEL ULite SOM:
From the Carrier imx6ul-lynx-som0013-cb002f.dts device tree:
[ 1.163365] 2020000.serial: ttymxc0 at MMIO 0x2020000 (irq = 30, base_baud = 5000000) is a IMX
[ 1.923126] 21ec000.serial: ttymxc2 at MMIO 0x21ec000 (irq = 65, base_baud = 5000000) is a IMX
and from imx6ul-lynx-som0013.dtsi
pinctrl_uart1: uart1grp {
fsl,pins = <
MX6UL_PAD_UART1_TX_DATA__UART1_DCE_TX 0x1b0b1
MX6UL_PAD_UART1_RX_DATA__UART1_DCE_RX 0x1b0b1
>;
};
pinctrl_uart2: uart2grp {
fsl,pins = <
MX6UL_PAD_UART2_TX_DATA__UART2_DCE_TX 0x1b0b1
MX6UL_PAD_UART2_RX_DATA__UART2_DCE_RX 0x1b0b1
>;
};
pinctrl_uart2_flow: uart2grp-flow {
fsl,pins = <
MX6UL_PAD_UART2_TX_DATA__UART2_DCE_TX 0x1b0b1
MX6UL_PAD_UART2_RX_DATA__UART2_DCE_RX 0x1b0b1
MX6UL_PAD_UART2_CTS_B__UART2_DCE_CTS 0x1b0b1
MX6UL_PAD_UART2_RTS_B__UART2_DCE_RTS 0x1b0b1
>;
};
pinctrl_uart3: uart3grp {
fsl,pins = <
MX6UL_PAD_UART3_TX_DATA__UART3_DCE_TX 0x1b0b1
MX6UL_PAD_UART3_RX_DATA__UART3_DCE_RX 0x1b0b1
>;
};
pinctrl_uart3_flow: uart3grp-flow {
fsl,pins = <
MX6UL_PAD_UART3_TX_DATA__UART3_DCE_TX 0x1b0b1
MX6UL_PAD_UART3_RX_DATA__UART3_DCE_RX 0x1b0b1
MX6UL_PAD_UART3_CTS_B__UART3_DCE_CTS 0x1b0b1
MX6UL_PAD_UART3_RTS_B__UART3_DCE_RTS 0x1b0b1
>;
};
pinctrl_uart3_config: uart3grp-config {
fsl,pins = <
MX6UL_PAD_CSI_PIXCLK__GPIO4_IO18 0x80000000 /* MPUART1_ON */
MX6UL_PAD_SNVS_TAMPER5__GPIO5_IO05 0x80000000 /* MPUART1_DEN */
MX6UL_PAD_SNVS_TAMPER6__GPIO5_IO06 0x80000000 /* MPUART1_RXEN */
>;
};
pinctrl_uart8: uart8grp {
fsl,pins = <
MX6UL_PAD_LCD_DATA20__UART8_DCE_TX 0x1b0b1
MX6UL_PAD_LCD_DATA21__UART8_DCE_RX 0x1b0b1
>;
};
pinctrl_uart8_flow: uart8grp-1 {
fsl,pins = <
MX6UL_PAD_LCD_DATA20__UART8_DCE_TX 0x1b0b1
MX6UL_PAD_LCD_DATA21__UART8_DCE_RX 0x1b0b1
MX6UL_PAD_ENET2_RX_ER__UART8_DCE_RTS 0x80000000
MX6UL_PAD_ENET2_TX_CLK__UART8_DCE_CTS 0x80000000
>;
};
pinctrl_uart8_config: uart8grp-config {
fsl,pins = <
MX6UL_PAD_SNVS_TAMPER8__GPIO5_IO08 0x80000000 /* MPUART0_DEN */
MX6UL_PAD_SNVS_TAMPER9__GPIO5_IO09 0x80000000 /* MPUART0_RXEN */
MX6UL_PAD_CSI_MCLK__GPIO4_IO17 0x80000000 /* MPUART0_ON */
>;
};
Accessing the peripheral[edit | edit source]
Linux messages at boot time[edit | edit source]
... ... [ 1.211906] 2020000.serial: ttymxc0 at MMIO 0x2020000 (irq = 30, base_baud = 5000000) is a IMX [ 1.962230] 2024000.serial: ttymxc7 at MMIO 0x2024000 (irq = 31, base_baud = 5000000) is a IMX [ 1.974074] 21e8000.serial: ttymxc1 at MMIO 0x21e8000 (irq = 65, base_baud = 5000000) is a IMX [ 1.985128] 21ec000.serial: ttymxc2 at MMIO 0x21ec000 (irq = 66, base_baud = 5000000) is a IMX ... ...
Usage with stty[edit | edit source]
N.B. UART mapping respect to ttymxcX is the following one:
UART1 <-> ttymxc0 UART2 <-> ttymxc1 UART3 <-> ttymxc2 UART4 <-> ttymxc3 UART5 <-> ttymxc4 UART6 <-> ttymxc5 UART7 <-> ttymxc6 UART8 <-> ttymxc7 ...
For exmaple, using a loopback HW connection (RX shortcircuited to TX on UART232 port) it is possibile to test the send and receive data using the ttymxc2 device:
root@desk-mx6ul-lynx:~# stty -F /dev/ttymxc7 115200 -echo root@desk-mx6ul-lynx:~# cat /dev/ttymxc7 & [1] 266 root@desk-mx6ul-lynx:~# echo "Test loopback" > /dev/ttymxc7 Test loopback
Additional information[edit | edit source]
Serial ports can be used through the standard serial programming API.
For detailed information, please refer to the Serial Programming HOWTO at Serial-Programming-HOWTO
