UART即通用异步收发器，是一种支持全双工串行通信协议的接口。在i.MX6ULL处理器平台上，该处理器原生支持多达8路的UART接口，提供了丰富的串行通信能力。
针对ELF 1开发板，实际引出了4路UART接口供开发者使用，具体包括UART1、UART2、UART3以及UART7。其中UART1用于调试，UART2、UART3用于连接RS485收发芯片，UART7连接TTL转RS232芯片。
接下来，我们将针对上述几个UART接口逐一进行详细的配置说明。本次源码适配工作是在NXP i.MX6ULL EVK评估板的Linux内核源码（特定版本：Linux-imx_4.1.15）基础上进行的，以确保UART接口能够正确无误的在ELF 1开发板上工作。
一、 准备工作
elf@ubuntu:~/work$ tar jvxf linux-imx-imx_4.1.15_2.0.0_ga.tar.bz2 elf@ubuntu:~/work$ cd linux-imx-imx_4.1.15_2.0.0_ga/ elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ ls
elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ cp arch/arm/configs/imx_v7_mfg_defconfig arch/arm/configs/imx6ull_elf1_defconfig
elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ cp arch/arm/boot/dts/imx6ull-14x14-evk.dts arch/arm/boot/dts/imx6ull-elf1-emmc.dts
elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ vi arch/arm/boot/dts/Makefile
elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ vim build.sh
发布文章#!/bin/bash
export CPUS=`grep -c processor /proc/cpuinfo`
source /opt/fsl-imx-x11/4.1.15-2.0.0/environment-setup-cortexa7hf-neon-poky-linux-gnueabi
make distclean
make imx6ull_elf1_defconfig
make -j${CPUS}
rm -rf ./.tmp
make modules_install INSTALL_MOD_PATH=./.tmp/rootfs/
cd .tmp/rootfs/
tar -jcvf modules.tar.bz2 *elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ chmod 777 build.sh
）MX6UL_PAD_UART3_RX_DATA__UART3_DCE_RX MX6UL_PAD_UART3_TX_DATA__UART3_DCE_TX
pinctrl_uart3: uart3grp {
fsl,pins = <
MX6UL_PAD_UART3_RX_DATA__UART3_DCE_RX 0x1b0b1
MX6UL_PAD_UART3_TX_DATA__UART3_DCE_TX 0x1b0b1
>;
};
MX6UL_PAD_LCD_DATA17__UART7_DCE_RX MX6UL_PAD_LCD_DATA16__UART7_DCE_TX
pinctrl_uart7: uart7grp {
fsl,pins = <
MX6UL_PAD_LCD_DATA17__UART7_DCE_RX 0x1b0b1
MX6UL_PAD_LCD_DATA16__UART7_DCE_TX 0x1b0b1
>;
};
&uart1 {
pinctrl-names = “default”;
pinctrl-0 = <&pinctrl_uart1>;
status = “okay”;
}&uart2 {
pinctrl-names = “default”;
pinctrl-0 = <&pinctrl_uart2>;
/* fsl,uart-has-rtscts;
*/
/* for DTE mode,add below change */
/* fsl,dte-mode; */
/* pinctrl-0 = <&pinctrl_uart2dte>; */
status = “okay”;
}
&uart3 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_uart3>;
status = "okay";
};
&uart7 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_uart7>;
status = "okay";
};
. /opt/fsl-imx-x11/4.1.15-2.0.0/environment-setup-cortexa7hf-neon-poky-linux-gnueabi elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ make dtbs
elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ scp arch/arm/boot/dts/imx6ull-elf\1-emmc.dtb root@172.16.0.175:/run/media/mmcblk1p1/
root@ELF1:~# elf1_cmd_serialport ttymxc1 & root@ELF1:~# elf1_cmd_serialport ttymxc2 -o -b 9600 -t aabbccddeeff 1
root@ELF1:~# elf1_cmd_serialport ttymxc6 -o -b 9600 -t aabbccddeeff 1
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