Hi All, I added support for Silicon Labs CP210x to my development board kernel. On my development board CP210x chip is connected using USB bus. And I am sending data to CP210x using one external device. I write a program to read data on usb-serial (ttyUSB0) on development board. But I didn't get any data, --------------- --------- --------------------------- | external |-------> | CP210x | -------> | my developemnt | | device | | | | device | enable debug messages ----------------------------------------------------------------------------------------------------------------------------------------- # echo 1 > /sys/bus/usb-serial/drivers/generic/module/parameters/debug # cat /sys/bus/usb-serial/drivers/generic/module/parameters/debug Y # echo 1 > /sys/bus/usb-serial/drivers/cp210x/module/parameters/debug # cat /sys/bus/usb-serial/drivers/cp210x/module/parameters/debug Y ----------------------------------------------------------------------------------------------------------------------------------------- debug messages #demesg .... ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver ar71xx-ohci ar71xx-ohci: Atheros AR71xx built-in OHCI controller ar71xx-ohci ar71xx-ohci: new USB bus registered, assigned bus number 1 ar71xx-ohci ar71xx-ohci: irq 3, io mem 0x1b000000 usb usb1: configuration #1 chosen from 1 choice hub 1-0:1.0: USB hub found hub 1-0:1.0: 1 port detected usbcore: registered new interface driver usbserial USB Serial support registered for generic usbcore: registered new interface driver usbserial_generic usbserial: USB Serial Driver core Initializing USB Mass Storage driver... usbcore: registered new interface driver usb-storage USB Mass Storage support registered. usb 1-1: new full speed USB device using ar71xx-ohci and address 2 USB Serial support registered for cp210x usbcore: registered new interface driver cp210x cp210x: v0.09:Silicon Labs CP210x RS232 serial adaptor driver USB Serial support registered for pl2303 usbcore: registered new interface driver pl2303 pl2303: Prolific PL2303 USB to serial adaptor driver usb 1-1: configuration #1 chosen from 1 choice cp210x 1-1:1.0: cp210x converter detected usb 1-1: reset full speed USB device using ar71xx-ohci and address 2 usb 1-1: cp210x converter now attached to ttyUSB0 ...... ----------------------------------------------------------------------------------------------------------------------------------------- When I open ttyUSB0 for communication, debug messages are ----------------------------------------------------------------------------------------------------------------------------------------- #dmesg ... drivers/usb/serial/usb-serial.c: serial_install drivers/usb/serial/usb-serial.c: serial_open - port 0 drivers/usb/serial/cp210x.c: cp210x_open - port 0 drivers/usb/serial/cp210x.c: cp210x_get_termios_port - port 0 drivers/usb/serial/cp210x.c: cp210x_get_termios_port - baud rate = 115200 drivers/usb/serial/cp210x.c: cp210x_get_termios_port - data bits = 8 drivers/usb/serial/cp210x.c: cp210x_get_termios_port - parity = NONE drivers/usb/serial/cp210x.c: cp210x_get_termios_port - stop bits = 1 drivers/usb/serial/cp210x.c: cp210x_get_termios_port - flow control = NONE drivers/usb/serial/cp210x.c: cp210x_tiocmset_port - port 0 drivers/usb/serial/cp210x.c: cp210x_tiocmset_port - control = 0x0303 ..... ----------------------------------------------------------------------------------------------------------------------------------------- The debug messages I get when I send data from external device to developemnt board, ----------------------------------------------------------------------------------------------------------------------------------------- #demesg .... drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: usb_serial_port_work - port 0 drivers/usb/serial/usb-serial.c: usb_serial_port_work - port 0 drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: serial_write_room - port 0 drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [5E] drivers/usb/serial/usb-serial.c: serial_write - port 0, 1 byte(s) data [40] drivers/usb/serial/usb-serial.c: usb_serial_port_work - port 0 drivers/usb/serial/usb-serial.c: usb_serial_port_work - port 0 drivers/usb/serial/usb-serial.c: usb_serial_port_work - port 0 ----------------------------------------------------------------------------------------------------------------------------------------- Program to read data from ttyUSB0, running on development board ----------------------------------------------------------------------------------------------------------------------------------------- int main(void) { int UartFd; char ReadData[30]; int ReturnVal; UartFd = open("/dev/ttyUSB0", O_RDONLY); if ( UartFd < 0 ) { perror("Open"); } else { printf("Uart_Fd: %d\r\n", UartFd); } memset(ReadData, 0, sizeof(ReadData)); ReturnVal = read(UartFd, ReadData, sizeof(ReadData)); if ( ReturnVal < 0 ) { perror("Read"); } else { printf("ReturnVal: %d\r\n", ReturnVal); int i; for(i = 0; i < ReturnVal; i++) printf(" %2X ", ReadData[i]); } close(UartFd); return 0; } ----------------------------------------------------------------------------------------------------------------------------------------- My program didn't print any data on terminal. Is any body help me how to debug this issue, what is the problem. Thanks in advance, Thanks, Paras