RK3399实现uart、rs232、rs485以及接口光耦保护电路
rk3399 串口不够用，参考设计中增加了wk2124这颗拓展芯片，可以转出4路串口，电路如下dts配置只需要3步1、关闭uart4
&uart4 {
status = "disabled";
2、wk2124挂到spi1上面
&spi1 {
status = "okay";
spi_wk2xxx: spi_wk2xxx@00{
status = "okay";
compatible = "jinghong,spi-wk2xxx";
reg = <0x00>;
spi-max-frequency = <10000000>;
// power-gpio = <&gpio2 4 GPIO_ACTIVE_HIGH>;
//reset-gpio = <&gpio1 17 GPIO_ACTIVE_HIGH>;
reset-gpio = <&gpio1 19 GPIO_ACTIVE_HIGH>;
irq-gpio = <&gpio1 2 IRQ_TYPE_EDGE_FALLING>;
cs-gpio = <&gpio1 10 GPIO_ACTIVE_HIGH>;
/* rk3399 driver support SPI_CPOL | SPI_CPHA | SPI_CS_HIGH */
//spi-cpha; /* SPI mode: CPHA=1 */
//spi-cpol; /* SPI mode: CPOL=1 */
//spi-cs-high;
};
3、检查gpio复用
max232电路
光耦隔离
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