RS232 vs TTL

What is RS232?

When working with Serial Communication, you’ll bound to come across the term RS-232. What’s RS232 you may ask?

RS232 is the first serial communication protocol that’s widely used as a communication method for computers and devices by serial ports. Similar to your microcontroller serial signals, it transmits data a bit at one time.

RS232 works by connecting Data Transmission Equipment (DTE) and Data Communication Equipment (DCE), which has pins like TXD, RXD, and RTS&CTS.

  • TXD: Transmitter
  • RXD: Receiver
  • RTS: Request to Send
  • CTS: Clear to Send
  • GND: Ground

RS232 Features and Parameters:

Parameters RS232
Transmission Mode Simplex
Max connected devices 2 devices:
1 driver, 1 receiver
Max. transmission rate 20Kbps
Max. cable length 15m
Operation mode Single-ended (unbalanced type)
Features Short distance
1:1 connection


Advantages and Disadvantages of RS232


  • Low cost
  • Widely available and applicable due to its long presence in the telecommunications industry
  • Simple wiring and connectors with only max support for 1 driver and 1 receiver


  • Data transfer speed floats around 20kilobytes per second, slower than what we’re used to now
  • No more than 50 feet apart for a point-to-point connection between a computer and device

What is TTL serial?

TTL stands for Transistor-Transistor Logic, a serial communication commonly found in UART (universally asynchronous receiver/transmitter) transmission method, a method seen in most microcontrollers these days.

Advantages and Disadvantages of TTL Serial


  • Low cost
  • High availability
  • High compatibility with microcontroller
  • Ease of usage


  • Noisy, due to poor noise margin
  • Limited speed and frequency
  • Higher power consumption at higher frequencies

The two protocols differ in the following ways: 


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