UART
K5C 拓展引脚中如PL2，PL3默认配置成GPIO，可复用成UART
快速确认pin功能
$ ls longan/out/a133/c3/android/.board.dtb.dts.tmp
Android 平台
此文件需要编译后才会生成
从.dts.tmp文件中可以确认UART7是PL2，PL3配置，配置信息类似如下
s_uart0_pins_a: s_uart0@0 {
allwinner,pins = "PL2", "PL3";
allwinner,function = "s_uart0";
allwinner,muxsel = <2>;
allwinner,drive = <1>;
allwinner,pull = <1>;
};
...
s_uart0_pins_b: s_uart0@1 {
allwinner,pins = "PL2", "PL3";
allwinner,function = "io_disabled";
allwinner,muxsel = <7>;
allwinner,drive = <1>;
allwinner,pull = <1>;
};
...
uart7: uart@07080000 {
compatible = "allwinner,sun50i-uart";
device_type = "uart7";
reg = <0x0 0x07080000 0x0 0x400>;
interrupts = <0 112 4>;
clocks = <&clk_suart>;
pinctrl-names = "default", "sleep";
pinctrl-0 = <&s_uart0_pins_a>;
pinctrl-1 = <&s_uart0_pins_b>;
uart7_port = <7>;
uart7_type = <2>;
status = "disabled";
};
dts配置UART
单个引脚仅能用于一个功能，取消PL2，PL3 的GPIO配置
--- a/longan/device/config/chips/a133/configs/c3/kickpi-k5c.dts
+++ b/longan/device/config/chips/a133/configs/c3/kickpi-k5c.dts
@@ -1409,17 +1409,17 @@
linux,default_trigger = "default-on";
};
- PL2 {
- label = "PL2";
- gpios = <&r_pio PL 2 1 0 1 0>;
- linux,default_trigger = "default-on";
- };
-
- PL3 {
- label = "PL3";
- gpios = <&r_pio PL 3 1 0 1 0>;
- linux,default_trigger = "default-on";
- };
+ // PL2 {
+ // label = "PL2";
+ // gpios = <&r_pio PL 2 1 0 1 0>;
+ // linux,default_trigger = "default-on";
+ // };
+
+ // PL3 {
+ // label = "PL3";
+ // gpios = <&r_pio PL 3 1 0 1 0>;
+ // linux,default_trigger = "default-on";
+ // };
打开UART7
--- a/longan/device/config/chips/a133/configs/c3/kickpi-k5c.dts
+++ b/longan/device/config/chips/a133/configs/c3/kickpi-k5c.dts
+&uart7 {
+ status = "okay";
+};
测试UART
首先连接好硬件，RX连接TX，GND连GND
板端可通过microcom进行测试
microcom -s 115200 /dev/ttyS2
另一端可通过 Mobaxterm 或其他串口工具进行测试
GPIO
Linux-4.9
gpios = <&r_pio PL 0x4 0x0 0x1 0x0 0x1>
指向哪个pio，属于cpus要用**&r_pio**
哪个bank
当前bank中哪个引脚
复用类型
上下拉，值为0x1时采用默认值
驱动能力，值为0x0时采用默认值
输出电平，只有output才有效
使用上述方式配置gpio时，需要驱动调用以下接口解析dts的配置参数：
int of_get_named_gpio_flags(struct device_node *np, const char *list_name, int index,
enum of_gpio_flags *flags) 拿到gpio的配置信息后
查看pin配置
cd /sys/kernel/debug/sunxi_pinctrl
echo PC2 > sunxi_pin
cat sunxi_pin_configure
console:/ # cat /d/pinctrl/pio/pinmux-pins | grep 118
pin 118 (PD22): (MUX UNCLAIMED) pio:118
console:/ # cat /d/pinctrl/pio/pinmux-pins | grep 130
pin 130 (PE2): (MUX UNCLAIMED) pio:130
console:/ #
WATCHDOG
内核配置
CONFIG_WATCHDOG=y
CONFIG_SUNXI_WATCHDOG=y
驱动路径
longan/kernel/linux-4.9/drivers/watchdog/sunxi_wdt.c
写入任意内容（大写字母‘V’除外），开启看门狗，16s内需要写入一次
echo A > /dev/watchdog
开启看门狗
echo V > /dev/watchdog