Introduction: USB to Serial / TTL Adapter to Program ATmega328p (w/out DTR Pin!)

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This will help you upload code to an atmega328p for your standalone arduino project using USB to serial / TTL adapter!

Step 1:

First let’s see if the adapter’s working.

Plug in the adapter >> Open Arduino IDE >> Select the proper COM port >> Open Serial Monitor >> then type in “Hello World”, it should print “Hello World” in the monitor, if not something is wrong


Step 2: Fixing the Adapter's Driver

Device Manager >> Ports (COM & LPT)

If there is a yellow triangle next to “Prolific USB-to-Serial Comm Port”, that means correct driver version is not installed.

(Click this for more info)

Uninstall your existing driver (Control Panel >> Uninstall a program)

Download driver

Then install and done!

Do step 1 again to see if the adapter is now working

Step 3: Make the Necessary Wirings

For atmega328p on a breadboard, make the following connections (also, add an LED in series with a 100 ohm resistor on atmega328p pin 19/digital pin 13 for testing later)


1. Pushbutton (normally open)

2. 1 10kohm resistor

3. 2 22pF ceramic capacitors

4. Atmega328p

5. 16 MHz crystal oscillator

Step 4: Atmega328p Pinout

Step 5: Uploading Codes

For uploading code:

1. First make the following connections with the USB to Serial/TTL Adapter

USB to Serial/TTL Adapter >>>Atmega328p

5V >>> 5V rail

GND >>> GND rail

TXD >>> Pin 2 / RX pin

RXD >>> Pin 3 / TX pin

2. Open Arduino IDE >> File >> Examples >> Basics >> Blink

3. Press the pushbutton >> Hit upload

4. Keep on pressing if it says “Compiling sketch…”

5. Release the button as soon as it says “Uploading…”

6. Done!