How to use
Requirements
Already flashed Jetson
Carrierboard that supports UART
UART cable to connect to the carrierboard
Hardware setup
Loopback
The loopback is mostly used for testing the TTY interface and is a good start to get used to it. Its only required to connect one cable from the UART TX to the UART RX signal.
System to System
If you want to communicate between two system, then you have to connect the UART RX and TX signals crossed with the ones from the other signal.
Software Setup
Minicom is a terminal tool to simplify the configuration and the usage of the UART port that you want to use.
Install minicom
In case you do not have Minicom already installed use the following command to install it on your Jetson:
sudo apt-get install minicom Check tty device
ls -l /dev/ttyS* /dev/ttyTHS*Open minicom
Now that everything is set up get the debug logs, you just have to start Minicom with the following parameters:
sudo minicom -D /dev/ttyTHS0Your terminal should now look like something like this
Welcome to minicom 2.7.1
OPTIONS: I18n
Compiled on Aug 13 2017, 15:25:34.
Port /dev/ttyTHS0
Press CTRL-A Z for help on special keys
Configure TTY Port
Start Stop Bits
There is always a Start bit which starts with a low bit pulse and a Stop bit which stops with a high bit pulse. Between the Start and Stop bit are the programmable numbers of data bits (typically between 5 to 8)
Hardware Flow Control
Requirements:
RTS data line (Request to Send)
CTS data line (Clear to Send)
These lines are cross-connected between two devices. The RTS line is used to output if it is ready to accept new data and the CTS is used to read if it is allowed to send data to the other device.
Software Flow Control
Requirements:
RX (Receiver)
TX (Transmitter)
GND (Ground)
The Transmission in a Software Flow Control is started and stopped by sending special flow control characters. The flow control character are send from the Transmitter to the Reciever line.
Special flow control characters:
XON (Allow transmission from device, control character: DC1 ^Q, ASCII dec 17)
XOFF (Should halt transmission from device, control character: DC3 ^S, ASCII dec 19)
Example: Jetson 1 sending XOFF to Jetson 2 => Jetson 2 should halt transmitting to A until Jetson 1 sends XON to Jetson 2
Differences
Extra wires for Start/Stop transmitting
Special Character which are send over normal data line
Baud rate
The baud rate is the amount of bits that get transmitted per second.
Example: 1 bit per 200 millisecond is 5 baud
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Change settings in minicom
Open you minicom terminal and press [CTRL-A] O to open up the configuration window
Welcome to minicom 2.7.1
OPTIONS: I18n
Compiled on Aug 13 2017, 15:25:34.
Port /dev/ttyTCU0, 09:43:54
Press CTRL-A Z for help on special keys
+-------[configuration]--------+
| Filenames and paths |
| File transfer protocols |
| Serial port setup |
| Modem and dialing |
| Screen and keyboard |
| Save setup as configuration |
| Save setup as.. |
| Exit |
+------------------------------+Press "Serial port setup" to continue
Welcome to minicom 2.7.1
OPTI+-----------------------------------------------------------------------+
Comp| A - Serial Device : /dev/ttyTCU0 |
Port| B - Lockfile Location : /var/lock |
| C - Callin Program : |
Pres| D - Callout Program : |
| E - Bps/Par/Bits : 115200 8N1 |
| F - Hardware Flow Control : Yes |
| G - Software Flow Control : No |
| |
| Change which setting? |
+-----------------------------------------------------------------------+
| Screen and keyboard |
| Save setup as configuration |
| Save setup as.. |
| Exit |
+------------------------------+In this Panel you can configure:
Change Baudrate (E)
Bautrate Start bit Parity bit Stop bit
115200 8 N 1Toggle Hardware Flow Control (F)
Toggle Software Flow Control (G)
After changing your settings press Enter to save changes and go to Exit to close the configuration
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