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doc:hardware:port.serial [2013/04/24 19:04]
brnt
doc:hardware:port.serial [2014/03/21 23:02] (current)
bigbrick added hint to use SubD9 pins instead of soldering
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For help with the latter two, see [[soldering]]. But even if there is 9-pin D connector, beware the Voltage levels! For help with the latter two, see [[soldering]]. But even if there is 9-pin D connector, beware the Voltage levels!
 +
 +Hint: in case of unpopulated holes try fitting the pins from a disassembled SubD9 male plug into the holes instead of soldering the cable directly to the board. Fit perfectly on unbricked Asus and TP-Link routers and leaves no trace.
If the serial port is not readily accessible from the exterior of the device enclosure, you have some choices: If the serial port is not readily accessible from the exterior of the device enclosure, you have some choices:
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You will also need a terminal emulation program on your computer, such as minicom, hyperterminal, etc.  The terminal emulation program needs to be configured to be compatible with your device, in particular, with regard to baud rate and flow control.  If you are using only three wires (GND, TX, and RX) then hardware flow control should be turned off; you aren't using the pins (RTS and CTS) necessary for it to work.  Rarely, the baud rate that the device expects //might// be different in the bootloader and the running firmware; if so, you'll need to modify the baud rate settings in your terminal emulator after the firmware boots up. You will also need a terminal emulation program on your computer, such as minicom, hyperterminal, etc.  The terminal emulation program needs to be configured to be compatible with your device, in particular, with regard to baud rate and flow control.  If you are using only three wires (GND, TX, and RX) then hardware flow control should be turned off; you aren't using the pins (RTS and CTS) necessary for it to work.  Rarely, the baud rate that the device expects //might// be different in the bootloader and the running firmware; if so, you'll need to modify the baud rate settings in your terminal emulator after the firmware boots up.
 +Troubleshooting parts:
If you get something like this during the bootcycle (output is garbled) If you get something like this during the bootcycle (output is garbled)
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then probably the GND is not connected (soldered?) well. The router wont listen to any keyboard actions. then probably the GND is not connected (soldered?) well. The router wont listen to any keyboard actions.
After solving the problem output should look fine. After solving the problem output should look fine.
 +
 +If you successfully receive router bootup logs but seem unable to send data (e.g. some keyboard input which might be required to intercept bootup, and where you're unable to stop continued kernel bootup), then this may be due to having configured the connection as hardware flow control rather than software (happened on TL-WDR3600 in my case).
===== Considerations ===== ===== Considerations =====
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If you've found a good cell phone cable to use, you merely need to determine which wires are the VCC, GND, TX, and RX connections. Usually the VCC is red and the GND is black, but the other colors may vary (though blue and orange are common). There should be no need to modify the PCB embedded in the cable. If you've found a good cell phone cable to use, you merely need to determine which wires are the VCC, GND, TX, and RX connections. Usually the VCC is red and the GND is black, but the other colors may vary (though blue and orange are common). There should be no need to modify the PCB embedded in the cable.
-One type of the "Made in China" ones, not mentioned at http://www.nslu2-linux.org/wiki/HowTo/AddASerialPort ist the "S30880-S5601-A802-1"; its WHITE wire is data out (TX) and the ORANGE one is data in (RX), VCC and GND are red and black. Its a 3.3V converter built with the MAX3386E chip.+One type of the "Made in China" ones, not mentioned at http://www.nslu2-linux.org/wiki/HowTo/AddASerialPort ist the "S30880-S5601-A802-1"; its WHITE wire is data out (TX) of the DTE (PC) and conntcts to the RX of the DCE (Router); the ORANGE one is data in (RX) of the DTE (PC) and conntcts to the TX of the DCE (Router), VCC and GND are red and black. Its a 3.3V converter built with the MAX3386E chip.
=== MAX232 Kits === === MAX232 Kits ===
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===== Finding Serial Console ===== ===== Finding Serial Console =====
-First, check the OpenWrt wiki page describing your hardware and do a Google search. Most of the time, the serial port(s), if they exist, have already been documented by others.+First, check the OpenWrt wiki page describing your hardware and do a Google search. Most of the time, the serial port(s), if they exist, have already been documented by others. If methods listed here are not enough for you, consider to go deeper reading http://www.devttys0.com/2012/11/reverse-engineering-serial-ports/
==== Piezoelectric buzzer method ==== ==== Piezoelectric buzzer method ====

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doc/hardware/port.serial.1366823097.txt.bz2 · Last modified: 2013/04/24 19:04 by brnt