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diff --git a/_site/log/arduino-uno/index.html b/_site/log/arduino-uno/index.html index 45f6456..95681a4 100644 --- a/_site/log/arduino-uno/index.html +++ b/_site/log/arduino-uno/index.html @@ -2,12 +2,12 @@ <html> <head> <meta charset="utf-8"> - <title>How to configure ATmega328P microcontrollers to run at 3.3V and 5V</title> + <title>ATmega328P at 3.3V and 5V</title> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> - <title>How to configure ATmega328P microcontrollers to run at 3.3V and 5V</title> + <title>ATmega328P at 3.3V and 5V</title> <link rel="stylesheet" href="/assets/css/main.css"> <link rel="stylesheet" href="/assets/css/skeleton.css"> </head> @@ -41,17 +41,11 @@ <main> <div class="container"> <div class="container-2"> - <h2 class="center" id="title">HOW TO CONFIGURE ATMEGA328P MICROCONTROLLERS TO RUN AT 3.3V AND 5V</h2> + <h2 class="center" id="title">ATMEGA328P AT 3.3V AND 5V</h2> <h6 class="center">10 JUNE 2025</h5> <br> - <div class="twocol justify"><p>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.</p> - -<p>The steps that follow refer to the following pinout.</p> + <div class="twocol justify"><p>Quick reference for wiring ATmega328P ICs at 5V and 3.3V. 5V uses 16MHz +crystal, 3.3V uses 8MHz.</p> <table style="border: none; width: 100%;"> <tr style="border: none;"> @@ -66,59 +60,38 @@ oscillator.</p> </tr> </table> -<h2 id="5v-16mhz-configuration">5V-16MHz configuration</h2> - -<p>Powering ATmega328P microcontrollers with 5V is the most common setup. This is -also how Arduino Uno boards are wired.</p> - -<p>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.</p> - -<p><a href="Makefile">Here’s</a> a sample Makefile for compiling C programs for ATmega328P -microcontrollers using avr-gcc/avrdude toolchain.</p> - -<h2 id="33v-8mhz-configuration">3.3V-8MHz configuration</h2> - -<p>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.</p> - -<p>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).</p> - -<p>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.</p> - -<p>Power up the the ATmega328P by connecting its V<sub>CC</sub> 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.</p> - -<p>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. -<a href="3v3.Makefile">Here’s</a> a sample Makefile with adjusted parameters (e.g., baud -rate) for an 8MHz clock.</p> +<h2 id="5v-16mhz">5V-16MHz</h2> + +<p>Standard setup. How Arduino Uno boards are wired.</p> + +<p>Connections: Pin 1 → 5V via 10kΩ resistor. Pins 9/10 → 16MHz crystal via 22pF +capacitors to ground. Pins 7/20/21 → 5V supply. Pins 8/22 → ground. Add 0.1μF +decoupling caps between pins 7/20/21 and ground.</p> + +<p>Sample Makefile: <a href="Makefile">Makefile</a></p> + +<h2 id="33v-8mhz">3.3V-8MHz</h2> + +<p>Electrical connections identical to 5V circuit. Replace 5V with 3.3V supply, +16MHz crystal with 8MHz.</p> + +<p>Problem: ATmega328P ships configured for 5V. Must modify fuses (BOD level, +etc.) and replace bootloader. Standard Arduino bootloader expects 16MHz—needs +8MHz version.</p> + +<p>Solution: Use Arduino Uno as ISP. Upload ‘ArduinoISP’ sketch from Arduino IDE. +Connect SPI pins (ATmega328P ↔ Uno), Uno’s SS pin → ATmega328P RESET pin. Power +ATmega328P from Uno’s 5V pin during programming.</p> + +<p>Arduino IDE: Select ‘ATmega328P (3.3V, 8MHz)’ processor, ‘Arduino as ISP’ +programmer. Burn bootloader via tools menu.</p> + +<p>Sample Makefile (8MHz): <a href="3v3.Makefile">Makefile.3v3</a></p> <h2 id="remarks">Remarks</h2> -<p>In both configurations, if you intend to use the ATmega328P’s analog-to-digital -converter with the internal 1.1V or AV<sub>cc</sub> voltage as reference, do -not connect AREF (pin 21) to V<sub>cc</sub>. Refer to section 23.5.2 in the -datasheet for more information.</p> +<p>Don’t connect AREF (pin 21) to V<sub>cc</sub> if using ADC with internal 1.1V +or AV<sub>cc</sub> reference. See datasheet section 23.5.2.</p> </div> <p class="post-author right">by W. D. Sadeep Madurange</p> |