TTL vs rs232- Differences, Upsides, and Downsides

The Serial communication method is one of the most reliable data transmission modes over long distances. We will expound on the two main protocols in serial communication; TTL vs. rs232 serial. Hence, for an elaborate explanation of how these modes work, read on. 

Overview of TTL vs rs232

An rs32 Cable

Fig 1: An rs32 Cable

A serial signal is a mode of sending a single bit of data at a time. Hence, rs232 is the primary serial communication protocol. It connects Data Transmission Equipment (DTE) and Data Communication Equipment (DCE). 

On the other hand, Transistor-Transistor Logic (TTL) is a serial communication mode common in universally asynchronous receiver/transmitter (UART). The UART is the transmission technique synonymous with a wide range of most present-day microcontrollers. 

Noteworthy, serial transmission at the TTL level is between 0V and Vcc. 

RS232 Features and Parameters

An rs232 cable

Fig 2: An rs232 cable

  1. First, It is a full-duplex protocol featuring a 1:1 connection
  2. Also, it has a simplex transmission mode
  3. Thirdly, the maximum number of devices you can connect is 2 (Has 1 receiver and 1 driver)
  4. And it features a 20Kbps maximum transmission rate
  5. Fifthly, it’s a single-ended serial communication protocol for short-distance transmissions.  
  6. Also, any signal line voltage has a negative logic relationship

Advantages and disadvantages of TTL vs rs232

Conventional rs232 ports

Fig 3: Conventional rs232 ports

Check out the advantages and disadvantages of rs232:

Advantages of rs232

  1. It is widely available and also cheap. 
  2. Also, it requires simple wiring and few connectors; it only has 1 driver and 1 receiver. 

Disadvantages of rs232

  1. RS-232 signals have relatively slow data transfer speeds of approximately 20kilobytes per second. 
  2. Secondly, you cannot set it at a distance of more than 50ft between a device and a PC. 

Below are the merits and demerits of TTL:

Advantages of TTL serial

  1. It is readily available, and it is also cheap.
  2. Also, it is easy to use
  3. Thirdly, it is widely compatible with most microcontrollers.

Disadvantages of TTL serial

  1. It features a poor noise margin; hence relatively noisy
  2. Secondly, it has relatively high power consumption, especially at high frequencies. 
  3. Furthermore, a TTL signal has relatively low speed and frequency. 

TTL vs rs232: What’s the difference?

A USB to TTL convertor

Fig 4: A USB to TTL convertor

The two protocols differ in the following ways: 

Also, note that the two feature inverted logic levels. In this case, the inversion is between the“1”s and “0”s. 

How to make RS232 to TTL UART Converter

Male and Female DB9 connectors

Fig 5: Male and Female DB9 connectors


You will need the following materials for this project: 

  • Wire pieces
  • A Female DB9 connector
  • A 7805 regulator
  • Approximately one to five meters of a 4-wire cable
  • Two 1N4148 diodes
  • A  MAX232 IC
  • 47uF, 100uF electrolyte capacitors (1 each)
  • Four 4.7uF electrolyte capacitors, namely C3, C4, C5, C6
  • One 3.5mm stereo audio male connector
  • Soldering wire and oil. 

Connection Procedure

First, solder the four 4.7uF capacitors to the IC. The following table will come in handy during this process: 

Next, connect the power regulator to the MAX232 IC as follows: 

Now its time to connect the other capacitors to the 7805 regulators and MAX232 IC as follows: 

  1. First, connect the 47uF Capacitor positive pin to pin 16 of the MAX232 and the negative pin to the IC’s pin 15. 
  2. Also, connect the 100uF Capacitor positive pin to supply regulator’s pin 1 and the negative pin to pin 2. 

Next, connect one of the 1N4148 diode’s negative pins to pin 1 of the supply regulator. Also, attach C5 + pin to pin 2 of the voltage regulator via a small wire. 

Further, attach small wires on DB9 connector pins to make the following connections: 

Also, connect Pin 2 of the voltage regulator and MAX232 IC’s pins 9 and 10 to the 3.5mm audio connector. It’s best to insert insulators between wires that can touch to prevent short-circuiting. 

Lastly, cover the DB9 connector and test the device you’ve created. Remember to set the serial port RTS/DTR.


Fig 6: Male and Female rs232 connectors

Is RS-232 compatible with TTL?

There is no compatibility of TTL with the RS232 standard. However, most of the RS232 serial ports for scanners are TTL ports. 

Can a TTL to RS232 converter use only transistors?

It is possible only to build simple TTL to RS232 converters using transistors. You will require only two transistors for this project. 


Above are the key differences between RS232 and TTL and their respective features. Besides, we’ve described how to assemble a simple RS232 to TTL converter. For more inquiries, communicate with us

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Emma Lu
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