View source for Uart

https://blog.mbedded.ninja/electronics/communication-protocols/uart-communication-protocol/

URT is a serial connection that was implemented without being standardized. UART chip 8250 and it's newer version 16450 was used as a parallel to serial interface between the processor and the slave device

RS232 was standardized in 1960 as EIA RS-232 and updated throughout the years with version TIA-232-F from 2012.

RS232 port (DE9 subcontractor / DB25) From a DTE Terminal to a DCE modem. The original 8250 had an 8 bit buffer. Tx, Rx, CTS Clear-to-Send, RTS Ready-to-Receive. RS232 has a lot of power and the voltage is between -15 and plus -15V. UART uses the voltage from the chips (e.g. 5V or 3.3V depending on the )



Tx/Rx and no clock signal. Instead stop start was used, problems with IRQ, every byte triggered an interrupt. Processor would context switch.

[    0.000000] earlycon: sbi0 at I/O port 0x0 (options <nowiki>''</nowiki>)

[    0.000000] printk: bootconsole [sbi0] enabled

console=ttyS0,115200 earlycon=sbi

==== History ====
https://www.youtube.com/watch?v=2XLZ4Z8LpEE

Teletype on a 20mA current loop


sysctl -w kernel.printk="2 4 1 7"

dmesg --console-off

dmesg -D

CTRL + A Beginning of the line

CTRL + C Break

CTRL + D Logout

CTRL + E End of the line

CTRL + H Backspace

CTRL + J Enter

CTRL + K Yank everything after the cursor

CTRL + U Yank everything before the cursor

CTRL + Y Paste

CTRL + L Clear the screen

CTRL + R Revers search through history

CTRL + T Swap characters