Difference between revisions of "Serial ports usage on Linux"
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(→Changing port parameters) |
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** change U-Boot ''consoledev'' envt variable, to tell Linux to display console on the LCD (for example): <pre class="apf> BIOS> setenv consoledev tty0</pre> | ** change U-Boot ''consoledev'' envt variable, to tell Linux to display console on the LCD (for example): <pre class="apf> BIOS> setenv consoledev tty0</pre> | ||
| − | ==Changing | + | ==Changing serial ports configuration== |
| − | * To get current | + | * To get current configuration (adapt serial port device name depending on your board, here ''ttymxc0''): |
<pre class=apf> | <pre class=apf> | ||
| − | # stty -F /dev/ | + | # stty -F /dev/ttymxc0 |
speed 115200 baud; | speed 115200 baud; | ||
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ^J; | intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ^J; | ||
| Line 32: | Line 32: | ||
* To only get actual speed: | * To only get actual speed: | ||
<pre class=apf> | <pre class=apf> | ||
| − | # stty -F /dev/ | + | # stty -F /dev/ttymxc0 speed |
115200 | 115200 | ||
</pre> | </pre> | ||
| − | * 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): | + | * 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): |
<pre class=apf> | <pre class=apf> | ||
| − | # stty -F /dev/ | + | # stty -F /dev/ttymxc1 raw -echo -echoe -echok |
| − | + | ||
</pre> | </pre> | ||
* To change baudrate of port 2 to 115200 : | * To change baudrate of port 2 to 115200 : | ||
<pre class=apf> | <pre class=apf> | ||
| − | # stty -F /dev/ | + | # stty -F /dev/ttymxc2 115200 |
</pre> | </pre> | ||
Revision as of 21:47, 20 July 2017
How to use the APF's serial ports on Linux.
Contents
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:
- /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 serial ports configuration
- To get current configuration (adapt serial port device name depending on your board, here ttymxc0):
# stty -F /dev/ttymxc0 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/ttymxc0 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):
# stty -F /dev/ttymxc1 raw -echo -echoe -echok
- To change baudrate of port 2 to 115200 :
# stty -F /dev/ttymxc2 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
