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@ -2,7 +2,7 @@
## Table of contents
* [UART](#uart)
* [Table of contents](#table-of-contents)
* [Table of contents](#table-of-contents)
* [What is it ?](#what-is-it-)
* [Identifying UART ports](#identifying-uart-ports)
* [Using a multimeter](#using-a-multimeter)
@ -10,7 +10,10 @@
* [Connect to serial port](#connect-to-serial-port)
* [WARNING](#warning)
* [Examples](#examples)
* [UART over BLE](#uart-over-ble)
* [Connection using a USB to TTL](#connection-using-a-usb-to-ttl)
* [Detect the baud rate](#detect-the-baud-rate)
* [Interact with UART](#interact-with-uart)
- [UART over BLE](#uart-over-ble)
## What is it ?
@ -18,15 +21,15 @@ UART stands for Universal asynchronous receiver transmitter. Used for serial com
UART peripherals are commonly integrated in many embedded devices. UART communication makes use of baud rate to maintain synchronism between two devices. The baud rate is the rate at which information is transferred in a communication channel.
With access to the UART, a user can see bootloader and operating system logs.
With access to the UART, a user can see bootloader and operating-system logs.
Generaly, the line is held high (at a logical 1 value) while UART is in idle state.
Generally, the line is held high (at a logical 1 value) while UART is in idle state.
We call the most common configuration **8N1** : eight data bits, no parity, and 1 stop bit.
We call the most common configuration **8N1**: eight data bits, no parity, and 1 stop bit.
## Identifying UART ports
A UART pinout has **four** ports :
A UART pinout has **four** ports:
* **TX** (Transmit)
* **RX** (Receive)
* **Vcc** (Voltage)
@ -34,7 +37,7 @@ A UART pinout has **four** ports :
![](https://re-ws.pl/wp-content/uploads/2017/09/pinout.jpg)
To find UART multiple solution :
To find UART multiple solution:
* Search on Internet
* Labeled on PCB
* Find candidates
@ -51,7 +54,7 @@ First identify the GRN pin, by using the multimeter in continuity mode.
Place the black probe on any grounded metallic surface, be it a part of the tested PCB or not. Then place the red probe on each of the ports. When you hear a beeping sound, you found a GND pin.
#### Vcc pin
Turn the multimeter to the DC voltage mode in and set it up to 20V of voltage. Keep the black probe on a grounded surface. Place the red probe on a suspeted pin and turn on the device.
Turn the multimeter to the DC voltage mode in and set it up to 20V of voltage. Keep the black probe on a grounded surface. Place the red probe on a suspected pin and turn on the device.
If the multimeter measures a constant voltage of either 3.3V or 5V, you've found the Vcc pin.
@ -66,10 +69,16 @@ If you've already identified the rest of the UART pins, the nearby fourth pin is
Otherwise, you can identify it because it has the lowest voltage fluctuation and lowest overall value of all the UART pins.
### Using a logic analyzer
A logic analyzer is an electronic instrument that captures and displays multiple signals from a digital system or digital circuit.
!!!!!!!!!!!!!!!DO THIS PART!!!!!!!!!!
To find the UART pins we will connect the pins to a logic analyzer and look for data being transmitted.
To find the UART pins we will connect the pins to a logic analyzer and look for data being transmitted. In the case of this device, bootloader and kernel logs are printed to this interface on startup, so we will expect to see data come across the transmit line of the UART device.2 This is what we will be looking for.
Make sure any system you're testing is **powered off** when you connect the logic analyzer's probes to it **to avoid short-circuiting**.
In the settings, change the **Speed (Sample Rate)** to 50 kS/s and the **Duration** to 20 seconds. As a rule, you should sample digital signals **at least four times faster than their bandwidth**. With serial communications, which are generally very slow, a 50 kS/s sampling rate is more than enough, although sampling faster than this does no harm. As for the duration, 20 seconds is enough time for the device to power on and start transmitting data.
In the case of this device, bootloader and kernel logs are printed to this interface on startup, so we will expect to see data come across the transmit line of the UART device.2 This is what we will be looking for.
https://medium.com/@shubhamgolam10/reverse-engineering-uart-to-gain-shell-de9019ae427a
@ -85,36 +94,37 @@ It's not a big deal if you confuse the UART RX and TX ports with each other, bec
![](https://vanhunteradams.com/Protocols/UART/uart_hardware.png)
!!!!!!!!!!!!!!!REDO THIS PART!!!!!!!!!!
### Connection using a USB to TTL
Once the ports are connected, plug the adapter into your computer. You now need to find the **device file descriptor**. To do that enter the following command : `sudo dmesg`.
Connect to UART using an USB to TTL, then find the `/dev/ttyUSB0` device in the `dmesg` command output. You need to create the `dialout` group for Debian or `uucp` for Manjaro :
Typically, it will be assigned to `/dev/ttyUSB0` **if you don't have any other peripheral devices attached**.
* `sudo usermod -a -G dialout username`
* `sudo gpasswd -a username uucp`
Under Ubuntu or Debian, a non-root user cannot have access to serial ports such as ttyS0 or ttyUSB0 if he is not a member of the **dialout** group ! The equivalent group on Arch based distributions is **uucp**. In other words, you just have to add yourself to this group to have access.
!!!!!!!!!!!!!!!REDO THIS PART!!!!!!!!!!
Ubuntu or Deiban: `sudo usermod -a -G dialout $USER`
Arch based: `sudo usermod -a -G uucp $USER`
#### Detect baud rate
##### Most common baud rate
### Detect the baud rate
#### Most common baud rate
The most common baud rates for UART are `9600`, `19200`, `38400`, `57600` and `115200`.
A table of other used but less common baud rates can be found here : [Here](https://lucidar.me/en/serialib/most-used-baud-rates-table/)
A table of other used but less common baud rates can be found here: [Here](https://lucidar.me/en/serialib/most-used-baud-rates-table/)
##### Auto-detect the baud rate using a script
Link : [baudrate.py](https://github.com/devttys0/baudrate/blob/master/baudrate.py)
#### Autodetect the baud rate using a script
Link: [baudrate.py](https://github.com/devttys0/baudrate/blob/master/baudrate.py)
```bash
# Download
# Download the script
wget https://raw.githubusercontent.com/devttys0/baudrate/master/baudrate.py
# Install serial
# Install serial dependency
pip2.7 install serial
# Run the script on "/dev/ttyUSB0"
python2.7 baudrate.py -p /dev/ttyUSB0
```
#### Interact with UART
Different command line tools to interract with UART :
### Interact with UART
Different command line tools to interact with UART:
```powershell
cu -l /dev/ttyUSB0 -s 115200
microcom -d -s 115200 -p /dev/ttyUSB0
@ -122,7 +132,7 @@ minicom -b 115200 -o -D /dev/ttyUSB0 # To exit GNU screen, type Control-A k
screen /dev/ttyUSB0 115200
```
Script to brute force a password protected UART :
Script to brute force a password protected UART:
```python
import serial, time
port = "/dev/ttyUSB0"
@ -145,13 +155,14 @@ with open('/home/audit/Documents/IOT/passwords.lst', 'r') as f:
It’s an emulation of serial port over BLE. The UUID of the Nordic UART Service is `6E400001-B5A3-F393-E0A9-E50E24DCCA9E`. This service exposes two characteristics: one for transmitting and one for receiving.
* **RX Characteristic** (UUID: 6E400002-B5A3-F393-E0A9-E50E24DCCA9E) : The peer can send data to the device by writing to the RX Characteristic of the service. ATT Write Request or ATT Write Command can be used. The received data is sent on the UART interface.
* **TX Characteristic** (UUID: 6E400003-B5A3-F393-E0A9-E50E24DCCA9E) : If the peer has enabled notifications for the TX Characteristic, the application can send data to the peer as notifications. The application will transmit all data received over UART as notifications.
* **RX Characteristic (UUID: 6E400002-B5A3-F393-E0A9-E50E24DCCA9E)** :
* The peer can send data to the device by writing to the RX Characteristic of the service. ATT Write Request or ATT Write Command can be used. The received data is sent on the UART interface.
* **TX Characteristic (UUID: 6E400003-B5A3-F393-E0A9-E50E24DCCA9E)** :
* If the peer has enabled notifications for the TX Characteristic, the application can send data to the peer as notifications. The application will transmit all data received over UART as notifications.
### Examples
* [nRF UART 2.0 - Nordic Semiconductor ASA](https://play.google.com/store/apps/details?id=com.nordicsemi.nrfUARTv2)
* [UART/Serial Port Emulation over BLE](https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v14.0.0%2Fble_sdk_app_nus_eval.html)
* [UART Over Bluetooth Low Energy](https://thejeshgn.com/2016/10/01/uart-over-bluetooth-low-energy/)
Example with Micro::bit :
* [https://makecode.microbit.org/v1/98535-28913-33692-07418](https://makecode.microbit.org/v1/98535-28913-33692-07418)
* [Using the micro:bit Bluetooth Low Energy UART (serial over Bluetooth)](https://support.microbit.org/support/solutions/articles/19000062330-using-the-micro-bit-bluetooth-low-energy-uart-serial-over-bluetooth-)