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Serial ports usage on Linux
How to use the APF's serial ports on Linux.
Generalities On Linux, all serial ports are driven the same way. Only their device nodes are changing to reflect the port type:
i.MX processor internal ports: on APF9328, APF27, APF51 & OPOS6UL: /dev/ttySMXN (with kernels <= 2.6.29) or /dev/ttymxcN (with kernels > 2.6.29) on APF28: /dev/ttySP[0-4] (general purpose serial ports) or /dev/ttyAMxx (debug serial ports) /dev/ttyUSBN for USB <-> serial converters /dev/ttySnN for 16550 compatible FPGA's IP Console port Console port is the default serial port on which you can interact with the board (U-Boot and Linux): it is serial port 0 (-> /dev/ttySMX0 or /dev/ttymxc0) on APF9328, APF27 & OPOS6UL it is serial port 2 (-> /dev/ttymxc2) on APF51 it is debug serial port 0 (-> /dev/ttyAM0 (2.6.35 kernel) or /dev/ttyAMA0 (3.x kernels)) on APF28 So, without software modifications, this port is not available to connect a MODEM or any other RS-232 device. If you want to use it as a normal serial port on Linux then: be sure that your device won't send data back in response of U-Boot boot's sequence change U-Boot consoledev envt variable, to tell Linux to display console on the LCD (for example): BIOS> setenv consoledev tty0 Changing serial ports configuration To get current configuration (adapt serial port device name depending on your board, here ttymxc0):
speed 115200 baud; intr = ^C; quit = ^; erase = ^?; kill = ^U; eof = ^D; eol = ^J; eol2 = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0; -brkint ixoff -imaxbel -iexten -echoctl To only get actual speed:
115200 By default serial ports are configured as terminal emulator (canonical mode). If you want to use them as "raw" serial port you will have to do first (example for port 1):
To change baudrate of port 2 to 115200 :
Sending/Receiving data In Linux console It is as simple as opening the device as a file and writing data to it:
To receive data (ASCII in that case):
With terminal (miniterm.py) By default, a simple terminal named «miniterm.py» is installed in the BSP. To use it on OPOS6UL, launch it with /dev port name and speed :
$ miniterm.py /dev/ttymxc1 115200 --- Miniterm on /dev/ttymxc1 115200,8,N,1 --- --- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H --- Hello world ! On OPOS6UL_DEV if Rx/Tx are not in loop, nothing will be prompted on key input. To see something prompted the Rx/Tx must be plugged together with a jumper on RaspberryPi connector (pin 8 and 10).
Statistics To have some statistics on serial port usage:
serinfo:1.0 driver revision: 0: uart:8006a000.serial mmio:0x8006A000 irq:214 tx:0 rx:0 CTS 1: uart:8006c000.serial mmio:0x8006C000 irq:215 tx:0 rx:0 CTS 3: uart:80070000.serial mmio:0x80070000 irq:216 tx:875195 rx:4024187 CTS 4: uart:80072000.serial mmio:0x80072000 irq:217 tx:0 rx:0 CTS