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Top Forums UNIX for Dummies Questions & Answers setserial not working on linux running on Beagleboard (ARM development board) Post 302569229 by julumme on Sunday 30th of October 2011 10:15:37 AM
Old 10-30-2011
setserial not working on linux running on Beagleboard (ARM development board)


I'm trying to develop an application to work with serial infra-red module, but I'm having difficulties to even get my module started. My HW is Beagleboard, which has 1 UART serial port, normally used for console, which I have disabled (I re-created the boot.scr, without the console arguments), and I have modified the getty config, not to try to attach to ttyO2.
On 3.x omap kernels, the serial port is now called ttyOx instead of ttySx, though I guess that doesn't really matter ? I guess the port and irq are the most important things..

During boot, I can see following information regarding the configuration:
[    0.000000] Kernel command line: console=tty0 root=/dev/mmcblk0p2 rootwait ro vram=12MB omapfb.mode=dvi:1280x720MR-16@60 fixrtc buddy=none mpurate=auto
[    0.000000] console [tty0] enabled
[    0.768524] omap_uart.0: ttyO0 at MMIO 0x4806a000 (irq = 72) is a OMAP UART0
[    0.768768] omap_uart.1: ttyO1 at MMIO 0x4806c000 (irq = 73) is a OMAP UART1
[    0.769012] omap_uart.2: ttyO2 at MMIO 0x49020000 (irq = 74) is a OMAP UART2
[    0.769226] omap_uart.3: ttyO3 at MMIO 0x49042000 (irq = 80) is a OMAP UART3

When system tries to load the lirc module (for infra-red) I get this
complain about IRQ being busy:
[   12.396392] lirc_serial: IRQ 74 busy

Now, I'm not sure now why that is still happening, as I think nobody should be connected to ttyO2 anymore. But anyway, around internet people say I should release the UART manually, and I try it with setserial, with strange reply:
ubuntu@omap:/etc$ sudo setserial /dev/ttyO2 uart none
Cannot set serial info: Invalid argument

If I try without sudo, I get "Permission denied"

Also strangely, when I try to look at the port status:
ubuntu@omap:/etc$ sudo setserial -g /dev/ttyO[0-3]
/dev/ttyO0, UART: undefined, Port: 0x0000, IRQ: 72
/dev/ttyO1, UART: undefined, Port: 0x0000, IRQ: 73
/dev/ttyO2, UART: undefined, Port: 0x0000, IRQ: 74
/dev/ttyO3, UART: undefined, Port: 0x0000, IRQ: 80

Shoudn't there be something in those port addresses ?
Does it matter that "MMIO" is used ? Normally IO port seems to be indeed 0x**** format, now the address for serial port is much higher (0x********)

Any ideas how I should proceed ?

Last edited by julumme; 10-30-2011 at 12:16 PM.. Reason: -

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ports(7)						 Miscellaneous Information Manual						  ports(7)

ports, port_names - Device (tty and lp) names for serial and parallel ports SYNOPSIS
Default Serial Ports: /dev/tty00 /dev/tty01 (not present on a single-port system) Parallel Port: /dev/lp0 DESCRIPTION
AlphaStation and AlphaServer systems provide one or two 9-pin serial communication ports. These ports are usually labelled 1 (COMM1) and 2 (COMM2), but they may be identified by different icons. Using the appropriate serial cable and terminator, you can connect a serial printer, external modem, or character-cell terminal to a serial port. Most AlphaStation and AlphaServer systems also provide one parallel port, for use with a parallel printer. When you add a device to your system, the installation documentation may instruct you to map the device pathname to the port. These devices are located in the /dev directory. For serial-line ports, the two default device pathnames are: This pathname always maps to 1, COMM1, the lowest port number, an icon for a terminal console, or the only serial port (on a single-port system). This pathname always maps to 2, COMM2, the next numbered port, or (if one serial port is labeled with an icon for a terminal console) the remaining serial port. If your system hardware has been extended to include additional serial ports, the pathnames /dev/tty02, /dev/tty03, and so forth, may also be available to you. However, most systems have only /dev/tty00 and /dev/tty01 as the device pathnames for serial ports. The one parallel port on an AlphaStation or AlphaServer may be labeled with the word printer or a printer icon. On some systems, the paral- lel port may not be labeled. The device pathname for the parallel port is /dev/lp0. Currently, Tru64 UNIX does not fully support parallel printers, so fewer devices are connected to this port as compared to serial ports. If you are connecting a terminal console to your system, it must be connected to the serial port mapped to /dev/tty00. For other serial devices, it does not matter which of the serial ports you choose for the connection. For example, suppose you are setting up a system that has two serial ports, labeled 1 and 2. You intend to use a serial-line terminal rather than a workstation monitor as the system console and also want to connect a serial-line printer to the system. In this case, you must connect the terminal to the port labeled 1 (with the device pathname /dev/tty00). Therefore, you must connect the printer to the remaining port labeled 2 (with the device pathname /dev/tty01). If, for the same type of system, you intend to use a workstation monitor as the system console, it does not matter which serial port you use for a serial-line printer or modem. In other words, you can connect the printer to either port 1 (with pathname /dev/tty00) or port 2 (with pathname /dev/tty01). When prompted to enter a /dev/tty** pathname by the lprsetup script or the Print configuration tool in the CDE Application Manager, you would specify /dev/tty00 if you connected the printer to port 1 or /dev/tty01 if you connected the printer to port 2. See the System Administration manual for more information on setting up consoles (including remote consoles) and printers. See the modem(7) reference page for more information on setting up modems. SEE ALSO
Commands: lprsetup(8) Devices: ace(7), modem(7) System Administration delim off ports(7)

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