Connect to UART- From start to finish

To interact with a UART interface, you would need:

• A multimeter

• an USB to UART TTL adapter

• jumper cables

• and in some cases: a soldering station

After opening the device follow:

1. Get an overview of what is available of the PCB board

   1. Checkout which chips are used

      1. Google the datasheet of each chip you find (model should be printed on top of the chip)

      2. It can be useful to take a picture of the PCB and label everything you can identify

         

         Example layout of an PCB
   2. Check for connector or test pads (can be quick wins to find a UART/JTAG etc.)

      1. Even better if we find actual pins, where we can connect jumper cables to:

      

      Uart pins exposed

      1. Also JTAG (where we need more pins) are very interesting targets

      

      JTAG-Connector

      
2. Check the pinout for the connectors:

   1. Put your multimeter in continuity mode (often a "sound" symbol):

      

      Multimeter in continuity mode
   2. This mode will check if there is a direct link between two points on the PCB

   3. Put one probe on the connector pad you want to test

   4. The other one goes on the chip (datasheet will tell you what pins are used for UART/SPI/JTAG)

      

      How to probe

   You need to find the GND (ground), TX (transmit) and RX(receive) pins to communicate with UART.

3. Now you need to connect the pins using jumper cables to the UART-USB-TTL adapter (make sure RX -> TX and TX->RX, as they have to be reversed). This can be done by soldering the cables onto the connector pins, plug them in or use clamps.

   

   UART connection
4. On your PC use the following command to communicate over UART (you may have to adjust the baud rate)

Linux

sudo minicom -D /dev/ttyUSB0 -b 115200
sudo picocom -b 115200 -r -l /dev/ttyUSB0

Windows

Using PuTTY (Windows):

• Select “Serial” and enter the COM port (e.g., COM3) and baud rate (115200).

1. If you see readable data: You done it correctly!

example bootlog

Congrats! You found your first serial connection! Check out the UART chapter on how to use this to dump the firmware from the device.