STM32MP157C-DK2->Develop on Arm® Cortex®-A7之 开启UART7串口功能
开启并测试STM32MP157C-DK2开发板上的uart7的收发功能。
根据en.MB1272-DK2-C01_Schematic可以得知STM32MP157C-DK2开发板的CN14的D0和D1为UART7的TX(gpio-pin:PE8)和RX(gpio-pin:PE7)，连接也比较方便，CN14连接器信号定义：
开发板上实际的位置：
查看SDK的源码，drivers/tty/serial/Stm32-usart.h得知Serial在dev下的名称位ttySTM*，如ttySTM0，ttySTM1，代码如下所示：
通过终端命令查看开发板启动的串口，只有ttySTM0启动了：
root@stm32mp1:/# cd dev/
root@stm32mp1:/dev# dmesg | grep ttySTM*
[ 0.000000] Kernel command line: root=/dev/mmcblk0p6 rootwait rw console=ttySTM0,115200
[ 0.517065] 40010000.serial: ttySTM0 at MMIO 0x40010000 (irq = 25, base_baud = 4000000) is a stm32-usart
[ 1.453140] console [ttySTM0] enabled
[ 4.290053] systemd[1]: Unnecessary job for dev-ttySTM0.device was removed.可查看开发板的dts文件确定ttySTM0是对应的uart编号，查看../STM32MP15-Ecosystem-v1.1.0/Developer-Package/stm32mp1-openstlinux-4.19-thud-mp1-19-10-09/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/linux-4.19.49/arch/arm/boot/stm32mp157c-dk2.dts
// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
/*
* Copyright (C) STMicroelectronics 2018 - All Rights Reserved
* Author: Alexandre Torgue .
*/
/dts-v1/;
#include "stm32mp157a-dk1.dts"
#include
/ {
model = "STMicroelectronics STM32MP157C-DK2 Discovery Board";
compatible = "st,stm32mp157c-dk2", "st,stm32mp157";
aliases {
serial3 = &usart2;
};
wifi_pwrseq: wifi-pwrseq {
compatible = "mmc-pwrseq-simple";
reset-gpios = <&gpioh 4 GPIO_ACTIVE_LOW>;
};
}; 代码里面只有关于Serial3的定义，将usart2定义为Serial3，用于蓝牙的串口通信。但是stm32mp157c-dk2.dts包含了"stm32mp157a-dk1.dts"，查看../STM32MP15-Ecosystem-v1.1.0/Developer-Package/stm32mp1-openstlinux-4.19-thud-mp1-19-10-09/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/linux-4.19.49/arch/arm/boot/stm32mp157c-dk1.dts
// SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause)
/*
* Copyright (C) STMicroelectronics 2018 - All Rights Reserved
* Author: Alexandre Torgue .
*/
/dts-v1/;
#include "stm32mp157c.dtsi"
#include "stm32mp157c-m4-srm.dtsi"
#include "stm32mp157cac-pinctrl.dtsi"
#include
#include
/ {
model = "STMicroelectronics STM32MP157A-DK1 Discovery Board";
compatible = "st,stm32mp157a-dk1", "st,stm32mp157";
aliases {
ethernet0 = ðernet0;
serial0 = &uart4;
serial1 = &usart3;
serial2 = &uart7;
}; 代码里定义了uart4为serial0，也就是ttySTM0，usart3为serial1，uart7为serial2。
关于uart4的配置，引脚为uart4_pins_a（在stm32mp157-pinctrl.dtsi有关于uart4_pins_a的定义），状态为开启：
&uart4 {
pinctrl-names = "default", "sleep", "idle", "no_console_suspend";
pinctrl-0 = <&uart4_pins_a>;
pinctrl-1 = <&uart4_sleep_pins_a>;
pinctrl-2 = <&uart4_idle_pins_a>;
pinctrl-3 = <&uart4_pins_a>;
status = "okay";
};关于usart3的配置，引脚为usart3_pins_b（在stm32mp157-pinctrl.dtsi有关于usart3_pins_b的定义），状态为关闭：
&usart3 {
pinctrl-names = "default", "sleep", "idle";
pinctrl-0 = <&usart3_pins_b>;
pinctrl-1 = <&usart3_sleep_pins_b>;
pinctrl-2 = <&usart3_idle_pins_b>;
status = "disabled";
};关于uart7的配置，引脚为uart7_pins_a（在stm32mp157-pinctrl.dtsi有关于uart7_pins_a的定义），状态为关闭：
&uart7 {
pinctrl-names = "default", "sleep", "idle";
pinctrl-0 = <&uart7_pins_a>;
pinctrl-1 = <&uart7_sleep_pins_a>;
pinctrl-2 = <&uart7_idle_pins_a>;
status = "disabled";
};查看../STM32MP15-Ecosystem-v1.1.0/Developer-Package/stm32mp1-openstlinux-4.19-thud-mp1-19-10-09/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/linux-4.19.49/arch/arm/boot/stm32mp157-pinctrl.dtsi.dts
关于uart4_pins_a的定义，UART4_TX-PG11，UART4_RX-PB2：
uart4_pins_a: uart4-0 {
pins1 {
pinmux = ; /* UART4_TX */
bias-disable;
drive-push-pull;
slew-rate = <0>;
};
pins2 {
pinmux = ; /* UART4_RX */
bias-disable;
};
}; 关于uart7_pins_a的定义，UART7_TX-PE8，UART7_RX-PE7：
uart7_pins_a: uart7-0 {
pins1 {
pinmux = ; /* USART7_TX */
bias-disable;
drive-push-pull;
slew-rate = <0>;
};
pins2 {
pinmux = ; /* USART7_RX */
bias-disable;
};
}; 关于usart3_pins_b的定义， USART3_TX-PB10，USART3_RX-PB12：
usart3_pins_b: usart3-1 {
pins1 {
pinmux = , /* USART3_TX */
; /* USART3_RTS */
bias-disable;
drive-push-pull;
slew-rate = <0>;
};
pins2 {
pinmux = , /* USART3_RX */
; /* USART3_CTS_NSS */
bias-disable;
};
}; 通过以上文件关于uart7的配置得知，uart7对应的串口名称为serial2，为关闭状态，如果需要使用还需开启，uart7默认的TX为PE8，RX为PE7，和CN14的D0和D1连接的GPIO引脚是一致的。
启动uart7
修改stm32mp157c-dk1.dts文件，启动uart7:
将
&uart7 {
pinctrl-names = "default", "sleep", "idle";
pinctrl-0 = <&uart7_pins_a>;
pinctrl-1 = <&uart7_sleep_pins_a>;
pinctrl-2 = <&uart7_idle_pins_a>;
status = "disabled";
};
改为
&uart7 {
pinctrl-names = "default", "sleep", "idle";
pinctrl-0 = <&uart7_pins_a>;
pinctrl-1 = <&uart7_sleep_pins_a>;
pinctrl-2 = <&uart7_idle_pins_a>;
status = "okay";
};修改好后，重新编译dtb并且更新到开发板上：
caiyong@caiyong-virtual-machine:~/STM32MPU_workspace/STM32MP15-Ecosystem-v1.1.0/Developer-Package$ source SDK/environment-setup-cortexa7t2hf-neon-vfpv4-openstlinux_weston-linux-gnueabi
caiyong@caiyong-virtual-machine:~/STM32MPU_workspace/STM32MP15-Ecosystem-v1.1.0/Developer-Package/stm32mp1-openstlinux-4.19-thud-mp1-19-10-09/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/linux-4.19.49$ make dtbs
CALL scripts/checksyscalls.sh
DTC arch/arm/boot/dts/stm32mp157a-dk1.dtb
DTC arch/arm/boot/dts/stm32mp157c-dk2.dtb
DTC arch/arm/boot/dts/stm32mp157c-dk2-a7-examples.dtb
DTC arch/arm/boot/dts/stm32mp157c-dk2-m4-examples.dtb
caiyong@caiyong-virtual-machine:~/STM32MPU_workspace/STM32MP15-Ecosystem-v1.1.0/Developer-Package/stm32mp1-openstlinux-4.19-thud-mp1-19-10-09/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/linux-4.19.49$ scp arch/arm/boo
t/dts/stm32mp157*.dtb [email protected]:/boot
stm32mp157a-dk1.dtb 100% 66KB 924.6KB/s 00:00
stm32mp157c-dk2-a7-examples.dtb 100% 67KB 814.2KB/s 00:00
stm32mp157c-dk2.dtb 100% 67KB 780.1KB/s 00:00
stm32mp157c-dk2-m4-examples.dtb 100% 68KB 1.0MB/s 00:00
stm32mp157c-ed1.dtb 100% 62KB 633.6KB/s 00:00
stm32mp157c-ev1-a7-examples.dtb 100% 72KB 1.4MB/s 00:00
stm32mp157c-ev1.dtb 100% 72KB 730.1KB/s 00:00
stm32mp157c-ev1-m4-examples.dtb 100% 72KB 835.6KB/s 00:00
重新开发板：
在开发板的命令终端是执行以下命令，会看到ttySTM2:
root@stm32mp1:~# cd /dev/
root@stm32mp1:/dev# ls
root@stm32mp1:/dev# ls ttySTM*
ttySTM0 ttySTM2测试UART7
使用一根USB转LVTTL的串口线连接开发板和电脑，然后在电脑上找到相应的串口号，启动串口调试助手，设置波特率为115200，检验位：无，数据位：8位，停止位：1位，然后打开该串口：
在开发板的命令终端上配置ttySTM2，115200波特率 8数据位 1停止位 无校验位，命令如下：
root@stm32mp1:/# stty -F /dev/ttySTM2 speed 115200 cs8 -parenb -cstopb通过ttySTM2发送"hello world"到电脑的串口调试助手，命令如下：
root@stm32mp1:/# echo "hello world" > /dev/ttySTM2串口调试助手显示收到的内容：
启动开发板的ttySTM2的接收功能，命令如下：
root@stm32mp1:/# cat /dev/ttySTM2通过串口调试助手的发送窗口发送内容给开发板，开发板回显到串口调试助手上，如下图所示：
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