From 1a4a6cb6d2aa2c8512e9637dc5dd95997321c444 Mon Sep 17 00:00:00 2001 From: Sadeep Madurange Date: Sun, 4 Jan 2026 17:57:39 +0800 Subject: Fix the search engine post. --- _log/_site/arduino-uno.html | 76 --------------------------------------------- 1 file changed, 76 deletions(-) delete mode 100644 _log/_site/arduino-uno.html (limited to '_log/_site/arduino-uno.html') diff --git a/_log/_site/arduino-uno.html b/_log/_site/arduino-uno.html deleted file mode 100644 index d8ffac4..0000000 --- a/_log/_site/arduino-uno.html +++ /dev/null @@ -1,76 +0,0 @@ -

This is a quick reference for wiring up ATmega328P ICs to run at 5V and 3.3V. -While the 5V configuration is common, the 3.3V configuration can be useful in -low-power applications and when interfacing with parts that themselves run at -3.3V. In this guide, the 5V setup is configured with a 16MHz crystal -oscillator, while the 3.3V configuration makes use of an 8MHz crystal -oscillator.

- -

The steps that follow refer to the following pinout.

- - - - - - -
- Pinout -

Pinout

- 		- Circuit -

Breadboard

-
- -

5V-16MHz configuration

- -

Powering ATmega328P microcontrollers with 5V is the most common setup. This is -also how Arduino Uno boards are wired.

- -

In this configuration, the microcontroller’s pin 1 is connected to 5V via a -10kΩ resistor. Pins 9 and 10 are connected to a 16MHz crystal oscillator via -two 22pF capacitors connected to ground. The microcontroller is powered by -connecting pins 7, 20, and 21 to a 5V DC power supply. Lastly, pins 8 and 22 -are connected to ground. In addition to the these connections, which are -required, it’s a good idea to add 0.1μF decoupling capacitors between pins 7, -20, and 21 and ground.

- -

Here’s a sample Makefile for compiling C programs for ATmega328P -microcontrollers using avr-gcc/avrdude toolchain.

- -

3.3V-8MHz configuration

- -

Electrical connections for running an ATmega328P at 3.3V are identical to that -of the 5V circuit. The only differences are that all the 5V connections are -replaced with a 3.3V power source and a 8MHz crystal oscillator takes the place -of the 16MHz crystal.

- -

However, standard ATmega328P chips are preconfigured to run at 5V. To run one -at 3.3V, we must first modify its fuses that control characteristics like the -BOD level. If a bootloader that expects a 16MHz clock (e.g., Arduino -bootloader) is pre-installed on the ATmega328P, it must be swapped with one -that accepts an 8MHz clock. To accomplish that, we need an in-system programmer -(ISP).

- -

Fortunately, we can turn an ordinary Arduino Uno board into an ISP by uploading -the ‘ArduinoISP’ sketch found in the Arduino IDE. The ISP communicates with the -microcontroller using a Serial Peripheral Interface (SPI). So, connect the SPI -port of the ATmega328P to that of the Arduino Uno, and the Uno’s SS pin -to the ATmega328P’s RESET pin.

- -

Power up the the ATmega328P by connecting its VCC to a 5V supply (we -can use Arduino Uno’s 5V pin). From the Arduino IDE, select ‘ATmega328P (3.3V, -8MHz)’ for processor from the tools menu. Also from the tools menu, select -‘Arduino as ISP’ as programmer. Finally, upload the new bootloader by selecting -‘Burn Bootloader’ from the tools menu.

- -

The ATmega328P is now ready to run at 8MHz with a 3.3V power supply. You can -upload programs to the ATmega328P as you normally would using avrdude. -Here’s a sample Makefile with adjusted parameters (e.g., baud -rate) for an 8MHz clock.

- -

Remarks

- -

In both configurations, if you intend to use the ATmega328P’s analog-to-digital -converter with the internal 1.1V or AVcc voltage as reference, do -not connect AREF (pin 21) to Vcc. Refer to section 23.5.2 in the -datasheet for more information.

- -- cgit v1.2.3