Difference between revisions of "Serial ports usage on Linux"
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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: | ||
* i.MX processor internal ports: | * i.MX processor internal ports: | ||
| − | ** on APF9328, APF27 | + | ** 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) | + | ** on [[APF28]]: ''/dev/ttySP[0-4]'' (general purpose serial ports) or ''/dev/ttyAMxx'' (debug serial ports) |
* ''/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 | ||
| Line 12: | Line 12: | ||
==Console port== | ==Console port== | ||
* Console port is the default serial port on which you can interact with the board (U-Boot and Linux): | * 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]] | + | ** 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 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]] | ** 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: | * 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 | ** 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): | + | ** 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> | ||
==Sending/Receiving data== | ==Sending/Receiving data== | ||
| − | * It is simple as opening the device as a file and writing data to it: | + | |
| + | === In Linux console === | ||
| + | * It is as simple as opening the device as a file and writing data to it: | ||
<pre class=apf> | <pre class=apf> | ||
| − | # echo "HELLO" > /dev/ | + | # echo "HELLO" > /dev/ttymxc0 |
</pre> | </pre> | ||
* To receive data (ASCII in that case): | * To receive data (ASCII in that case): | ||
<pre class=apf> | <pre class=apf> | ||
| − | # cat /dev/ | + | # cat /dev/ttymxc0 |
| + | </pre> | ||
| + | |||
| + | === 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 : | ||
| + | <pre class="apf"> | ||
| + | $ 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 ! | ||
| + | </pre> | ||
| + | |||
| + | 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 [[OPOS6ULDev#Connectors |RaspberryPi connector]] (pin 8 and 10). | ||
| + | |||
| + | ==Statistics== | ||
| + | * To have some statistics on serial port usage: | ||
| + | <pre class=apf> | ||
| + | # cat /proc/tty/driver/<driver_name> (for example ttyAPP on APF28, IMX-uart on OPOS6UL) | ||
| + | |||
| + | 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 | ||
</pre> | </pre> | ||
== Links == | == Links == | ||
| − | * [http://tldp.org/HOWTO/Serial-HOWTO.html Serial | + | * [http://tldp.org/HOWTO/Serial-HOWTO.html Serial UART manual in Linux] |
[[Category:Serial ports]] | [[Category:Serial ports]] | ||
Latest revision as of 09:58, 26 July 2018
How to use the APF's serial ports on Linux.
Contents
[hide]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
In Linux console
- It is as simple as opening the device as a file and writing data to it:
# echo "HELLO" > /dev/ttymxc0
- To receive data (ASCII in that case):
# cat /dev/ttymxc0
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:
# cat /proc/tty/driver/<driver_name> (for example ttyAPP on APF28, IMX-uart on OPOS6UL) 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
