Quick notes/intro for router debugging and rooting. Including tools, terms, and tactics.
UART is a serial protocol used for interecting with the system. May return a shell, and or access to the filesystem. Seperate from JTAG. - Voltage fluctuates at boot1 from 0 to 3.3/5.5v - Constant low value below VCC and above GND - Voltage is constant 0, has 4 traces in a crosss shape2 - Normally not used to if device already powered, should not fluctaute1 Fluctuation is caused from the debug messages being sent.2 Testing continuity of GND to other pins, shows other pins that may be groundedSquare outlined pin, normally is "pin 1"
Used for on-chip-debugging, generally allows for access to a GNU Debugger (GDB) for the JTAG host. Pinout for hidden console may be found with JTAGenum/JTAGulator. Then access GDB with a Bus Pirate or Shikra USB-to-Serial devices and debug applications using OpenOCD software.sudo dmesg | grep -iC 5 usbsudo screen -L /dev/ttyUSB0 115200Alternatively, use the Arduino IDE serial console. Useful when input is off with the screen utilityIn the screen command, 115200 is the baud rate of the serial communicationsThe baud rate can be determined using -https://github.com/devttys0/baudrate.git
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JTAGulator
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Identifies JTAG & UART pinouts.
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JTAGenum1
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Identifies JTAG pinouts
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Bus Pirate2
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FT232RL - USB to Serial, Use SOIC8 Clip to dump firmwarez
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Shikra3
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FT232H(Q) - USB to Serial
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RS-232 Generic Adapter4
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USB to Serial
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1 JTAGenum Setup Tutorial: https://p16.praetorian.com/blog/jtagulator-vs-jtagenum-tools-for-identifying-jtag-pins-in-iot-devices2 Bus Pirate Pinout Informationhttp://dangerousprototypes.com/docs/Common_Bus_Pirate_cable_pinouts3 Shikra Pinout [UART] D0 - TX, D1 - RXSee also, Adafruit FT232H Breakout - https://cdn-learn.adafruit.com/downloads/pdf/adafruit-ft232h-breakout.pdf4 Male DB9: GND - Pin 5, TX - Pin 3, RX - Pin 2
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