UART Reference

version 1.0

---

1. Overview

SSD20X provides 4 groups of uart (including a group of fuart), the pin corresponding to each MODE is as follows:

UART MODE	RX	TX	CTS	RTS
UART0	PM_UART_RX	PM_UART_TX	NA	NA
UART1	PAD_UART1_RX	PAD_UART1_TX	NA	NA
UART2	PAD_GPIO8	PAD_GPIO9	NA	NA
FUART(Without flow control)	PAD_FUART_RX	PAD_FUART_TX	NA	NA
FUART(With flow control)	PAD_FUART_RX	PAD_FUART_TX	PAD_FUART_CTS	PAD_FUART_RTS

---

2. UART Config

---

2.1. Config in Kernel

The main config is padmux.

---

2.2. Configure Padmode

1. Add padmux settings, open kernel\arch\arm\boot\dts\infinity2m-ssc010a-s01a-padmux-display.dtsi

   FUART(With flow control): when using MODE1, the default baud is 9600

   <PAD_FUART_RX          PINMUX_FOR_FUART_MODE_1  MDRV_PUSE_FUART_RX>,
   <PAD_FUART_TX          PINMUX_FOR_FUART_MODE_1  MDRV_PUSE_FUART_TX>,
   <PAD_FUART_CTS        PINMUX_FOR_FUART_MODE_1  MDRV_PUSE_FUART_CTS>,
   <PAD_FUART_RTS        PINMUX_FOR_FUART_MODE_1   MDRV_PUSE_FUART_RTS>,
   

   FUART(Without flow control): when using MODE2, the default baud is 9600 // /dev/ttyS2

   <PAD_FUART_RX    PINMUX_FOR_FUART_MODE_2    MDRV_PUSE_FUART_RX>,
   <PAD_FUART_TX    PINMUX_FOR_FUART_MODE_2    MDRV_PUSE_FUART_TX>,
   

   Configure uart0: the default baud is 115200 // /dev/ttyS0

   <PM_UART_RX    PINMUX_FOR_UART0_MODE_1    MDRV_PUSE_UART0_RX >,
   <PM_UART_TX    PINMUX_FOR_UART0_MODE_1    MDRV_PUSE_UART0_TX >,
   

   Configure uart1: the default baud is 9600 // /dev/ttyS1

   <PAD_UART1_RX    PINMUX_FOR_UART1_MODE_1   MDRV_PUSE_UART1_RX>,
   <PAD_UART1_TX    PINMUX_FOR_UART1_MODE_1   MDRV_PUSE_UART1_TX>,
   

   Configure uart2: the default baud is 9600 // /dev/ttyS3

   <PAD_GPIO8    PINMUX_FOR_UART2_MODE_2    MDRV_PUSE_UART2_RX>,
   <PAD_GPIO9    PINMUX_FOR_UART2_MODE_2    MDRV_PUSE_UART2_TX>,
   

After that, recompile the kernel and replace the kernel image to project to burn.

---

3. Use Uart

---

3.1. Confirm /dev/ttySx Used By Uart Pin

Check the dts to confirm which serialx the uart corresponds to.

Serialx corresponds to /dev/ttySx.

Fig 3-1 Check serialx

---

3.2. Use Application Layer

Refer to the following link for application layer usage:

https://blog.csdn.net/aaron_111/article/details/84876508

---

4. Uart Driver Architecture and debug

Figure 4-1 Uart driver framework

It can be seen from the above figure that the driver is mainly connected to the uart controller and the corresponding pad in series.

The following registers can be used to determine whether the corresponding uart controller and padmux are connected in series:

• Uart controller

  0x101e 0x53(16bit)

  

  Figure 4-2

  

  Figure 4-3

• Padmux

  0x101e 0x03(16bit)

  

  Figure 4-4