WK2204-spi to uart debugging record

Hardware

Chip introduction

WK2204(DataSheet) Is a spi extended UART chip, which implements spi extended 4 routes of uart. The expanded UART channel of the chip has the following features:

The baud rate, word length, and check format of each channel can be set independently, providing a maximum communication rate of 2 Mbps
Each channel has an independent 256-level FIFO receiving/sending. FIFO interrupts can be triggered programmatically according to user requirements and have timeout interrupt function
Each channel can independently set up advanced working modes such as IrDA infrared communication, RS485 automatic transceiver control, 9-bit network address automatic identification, software/hardware automatic flow control, etc.

circuit design

_Typical circuit design as shown in the figure:

The pin interruption requires an external pull-up resistance, typically 5.1K. The driver receives and receives data depending on the interrupt signal. If the interrupt signal is abnormal, the subsequence port cannot communicate properly.
Crystal Vibration Circuit, Requires 1M resistor in parallel with Crystal Vibration
SPI is connected to the SPI pin of the CPU (Xavier), the sub-serial port outputs TTL level, and the RS signal transceiver is connected
The RTS pin (only 2/4 of the sub-serial port) is used to control the transceiver/receiver conversion of the RS-485 transceiver in the RS485 automatic transceiver control working mode.

drive

Add Device Tree

As a SPI slave device, WK2204 SPI bus maximum rate cannot exceed 10M
INT and RTS are connected to CPU, and these two GPIO resources need to be added to the device tree
Frequency of Crystal Vibration in Device Tree

_Add the following device tree:

	spi@3230000{			// cpu is nvidia-jetson
		status = "okay"; 
 
		spi_test@00 { 
			compatible = "wkmic, wk2124spi"; 
			reg = <0>; 
 
			spi-max-frequency = <10000000>; 
 
			irq_gpio = <&tegra_main_gpio TEGRA194_MAIN_GPIO(T, 0) IRQ_TYPE_LEVEL_LOW>; 
			reset_gpio = <&tegra_main_gpio TEGRA194_MAIN_GPIO(M, 3) GPIO_ACTIVE_HIGH>; 
		}; 
	};

Add Driver

WK2204Official Driver Based on the Rockchip platform and the core-3.1 foundation, remove the relevant rockchip code:

-#include <linux/platform_data/spi-rockchip.h> 
... ... 
 
//#ifdef CONFIG_OF 
-static int rockchip_spi_parse_dt(struct device *dev) 
+static int spi_parse_dt(struct device *dev) 
... ... 
 
static int wk2xxx_probe(struct spi_device *spi) 
{ 
	... ... 
	 
+	irq = spi_parse_dt(&spi->dev); 
+	if(irq < 0) 
+		return 1; 
	 
	do 
	{ 
		wk2xxx_read_global_reg(spi,WK2XXX_GENA,dat); 
		printk(KERN_ERR "wk2xxx_probe()  GENA = 0x%X\n",dat[0]); //GENA=0X30 
		wk2xxx_write_global_reg(spi,WK2XXX_GENA,0xf5); 
		wk2xxx_read_global_reg(spi,WK2XXX_GENA,dat); 
		printk(KERN_ERR "wk2xxx_probe()  GENA = 0x%X\n",dat[0]); //GENA=0X35 
		wk2xxx_write_global_reg(spi,WK2XXX_GENA,0xf0); 
		wk2xxx_read_global_reg(spi,WK2XXX_GENA,dat); 
		printk(KERN_ERR "wk2xxx_probe()  GENA = 0x%X\n",dat[0]); //GENA=0X30 
	}while(0); 
/test spi //	 
 
-	irq = rockchip_spi_parse_dt(&spi->dev); 
-	if(irq < 0) 
-		return 1; 
	... ... 
} 
... ...
 
-static int wk2xxx_resume(struct spi_device *spi) 
-{ 
-	#ifdef _DEBUG_WK_FUNCTION 
-	printk(KERN_ALERT "%s!!--in--\n", __func__); 
-	#endif 
-   return 0; 
-} 
... ... 
 
static struct spi_driver wk2xxx_driver = { 
	.driver = { 
		.name           = "wk2xxxspi", 
		.bus            = &spi_bus_type, 
		.owner          = THIS_MODULE, 
		.of_match_table = of_match_ptr(rockchip_spi_wk2xxx_dt_match), 
	}, 
	 
	.probe          = wk2xxx_probe, 
	.remove         = wk2xxx_remove, 
-	.resume         = wk2xxx_resume, 
}

The RST pin level of WK2204 sub-serial port 4 can automatically control the sending and receiving of 485 chips. Official driver defaults to the RST pin pull up, instead of the default pull down:

+#define WK_RS485_FUNCTION 
...... 
 
static int wk2xxx_startup(struct uart_port *port)//i 
{ 
	... ...
	 
#ifdef WK_RS485_FUNCTION 
+	// Channel 4 is set to 485 functions 
+	if (s->port.iobase == 4) { 
-		wk2xxx_write_slave_reg(s->spi_wk,s->port.iobase,WK2XXX_RS485,0X02);	//default high 
+		wk2xxx_write_slave_reg(s->spi_wk,s->port.iobase,WK2XXX_RS485,0X03);	//default low 
		wk2xxx_write_slave_reg(s->spi_wk,s->port.iobase,WK2XXX_SPAGE,1); 
		wk2xxx_write_slave_reg(s->spi_wk,s->port.iobase,WK2XXX_RRSDLY,0X10); 
		wk2xxx_write_slave_reg(s->spi_wk,s->port.iobase,WK2XXX_SPAGE,0); 
	} 
#endif 
	... ... 
	 
}

The baud rate of WK2204 sub-serial port comes from the frequency division of crystal oscillation outside the chip. The official drive adapter is 11.0592 Mhz. Take 16Mhz crystal oscillation as an example, change to:

static void wk2xxx_termios( struct uart_port *port, struct ktermios *termios, 
            struct ktermios *old) 
{ 
	... ...
	 
	switch (baud) 
	{ 
		case 600: 
-			baud1=0x4; 
-			baud0=0x7f; 
-			pres=0; 
+			baud1=0x6; 
+			baud0=0x81; 
+			pres=0xb; 
			break; 
		case 1200: 
-			baud1=0x2; 
-			baud0=0x3F; 
-			pres=0; 
+			baud1=0x3; 
+			baud0=0x40; 
+			pres=0x5; 
			break; 
		case 2400: 
			baud1=0x1; 
-			baud0=0x1f; 
-			pres=0; 
+			baud0=0x9f; 
+			pres=0xb; 
			break; 
		case 4800: 
			baud1=0x00; 
-			baud0=0x8f; 
-			pres=0; 
+			baud0=0xcf; 
+			pres=0x5; 
			break; 
		case 9600: 
			baud1=0x00; 
-			baud0=0x47; 
-			pres=0; 
+			baud0=0x67; 
+			pres=0x3; 
			break; 
		case 19200: 
			baud1=0x00; 
-			baud0=0x23; 
-			pres=0; 
+			baud0=0x33; 
+			pres=0x1; 
			break; 
		case 38400: 
			baud1=0x00; 
-			baud0=0x11; 
-			pres=0; 
+			baud0=0x19; 
+			pres=0x1; 
			break; 
		case 76800: 
			baud1=0x00; 
-			baud0=0x08; 
-			pres=0; 
+			baud0=0x0c; 
+			pres=0; 
			break; 
		case 1800: 
-			baud1=0x01; 
-			baud0=0x7f; 
-			pres=0; 
+			baud1=0x2; 
+			baud0=0x2a; 
+			pres=0x9; 
			break; 
		case 3600: 
-			baud1=0x00; 
-			baud0=0xbf; 
-			pres=0; 
+			baud1=0x1; 
+			baud0=0x14; 
+			pres=0xc; 
			break; 
		case 7200: 
			baud1=0x00; 
-			baud0=0x5f; 
-			pres=0; 
+			baud0=0x89; 
+			pres=0xe; 
			break; 
		case 14400: 
			baud1=0x00; 
-			baud0=0x2f; 
-			pres=0; 
+			baud0=0x44; 
+			pres=0x7; 
			break; 
		case 28800: 
			baud1=0x00; 
-			baud0=0x17; 
-			pres=0; 
+			baud0=0x21; 
+			pres=0xc; 
			break; 
		case 57600: 
			baud1=0x00; 
-			baud0=0x0b; 
-			pres=0; 
+			baud0=0x10; 
+			pres=0x6; 
			break; 
		case 115200: 
			baud1=0x00; 
-			baud0=0x05; 
-			pres=0; 
+			baud0=0x07; 
+			pres=0xb; 
			break; 
		case 230400: 
			baud1=0x00; 
-			baud0=0x02; 
-			pres=0; 
+			baud0=0x03; 
+			pres=0x6; 
			break; 
		default: 
			baud1=0x00; 
			baud0=0x00; 
			pres=0; 
			break; 
	} 
	... ...
	 
}

debugging

View boot loads

_Driver loads successfully and generates four serial devices under / dev: ttysWK0, ttysWK1, ttysWK2, ttysWK3. Enter "dmesg | grep wk" or "ls/dev/ttysWK*" to see if the driver loaded successfully, as shown in the diagram:

_If the driver loading fails, detect if the RST signal is pulled up before the driver loading.

Check Serial Communication

_Windows System Installation Serial Debugging Assistant; The Ubuntu system recommends using the serial communication tool minicom (Reference) Usage method).

Data is out of order or missing

Check crystal vibration
Check harness
Detect INT signal
Change debugging tools

RS485 can only be received or not sent

Whether the driver enables 485 custom transceiver control functions
Oscilloscope Detecting RTS Signal

System Interrupt Response Exception

_If the system keeps responding to interruptions without data communication, as shown in the figure:

_Check the source of the interrupt to interrupt the DEBUG information (_DEBUG_WK_IRQ) if the register display chip does not issue an interrupt:

Check the interrupt mode of the driver settings and whether the low level triggers.
The oscilloscope detects the INT pin level before and after data communication. If it keeps pulling down, check the pull-up resistance value of the connection.

Reflection

_4 routes of uart data receipt are responded to by gpio interruption, which leads to higher CPU usage.

Posted by gardnc on Sun, 28 Nov 2021 11:15:33 -0800

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