Difference between revisions of "Serial ports usage on Linux"
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==Generalities== | ==Generalities== | ||
| − | On Linux all serial ports are driven the same way. Only their device nodes are changing to reflect the port type: | + | On Linux, all serial ports are driven the same way. Only their device nodes are changing to reflect the port type: |
| − | * ''/dev/ttySMXN'' (kernels <= 2.6.29) or ''/dev/ttymxcN'' (kernels > 2.6.29) | + | * i.MX processor internal ports: |
| + | ** on APF9328, APF27 & APF51: ''/dev/ttySMXN'' (kernels <= 2.6.29) or ''/dev/ttymxcN'' (kernels > 2.6.29) | ||
| + | ** on APF28: ''/dev/ttySP[0-4]'' | ||
* ''/dev/ttyUSBN'' for USB <-> serial converters | * ''/dev/ttyUSBN'' for USB <-> serial converters | ||
* ''/dev/ttySnN'' for 16550 compatible FPGA's IP | * ''/dev/ttySnN'' for 16550 compatible FPGA's IP | ||
Revision as of 10:46, 22 July 2012
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: /dev/ttySMXN (kernels <= 2.6.29) or /dev/ttymxcN (kernels > 2.6.29)
- on APF28: /dev/ttySP[0-4]
- /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):
- 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 port parameters
- To get current parameters (change serial port device name depending on your board):
# stty -F /dev/ttySMX0 speed 115200 baud; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ^J; eol2 = <undef>; 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:
# stty -F /dev/ttySMX0 speed 115200
- By default serial ports are configured as terminal emulator. If you want to use them as "raw" serial port you will have to do first (example for port 1):
# stty -F /dev/ttySMX1 raw # stty -F /dev/ttySMX1 -echo -echoe -echok
- To change baudrate of port 2 to 115200 :
# stty -F /dev/ttySMX2 115200
Sending/Receiving data
- It is simple as opening the device as a file and writing data to it:
# echo "HELLO" > /dev/ttySMX0
- To receive data (ASCII in that case):
# cat /dev/ttySMX0
