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| author | Sadeep Madurange <sadeep@asciimx.com> | 2025-12-08 17:34:35 +0800 |
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| committer | Sadeep Madurange <sadeep@asciimx.com> | 2025-12-08 21:05:19 +0800 |
| commit | 752a06ec0ebf20d6232b13f1ea53fe21fefcefbd (patch) | |
| tree | 690411afad8eb76216417a42de94135214cb2401 /_archive/arduino-uno.md | |
| parent | 20b0a045a7dc78f9728837fe5a1be8cf12caae4e (diff) | |
| download | www-752a06ec0ebf20d6232b13f1ea53fe21fefcefbd.tar.gz | |
Fix list indentation.
Diffstat (limited to '_archive/arduino-uno.md')
| -rw-r--r-- | _archive/arduino-uno.md | 82 |
1 files changed, 0 insertions, 82 deletions
diff --git a/_archive/arduino-uno.md b/_archive/arduino-uno.md deleted file mode 100644 index 6534c3c..0000000 --- a/_archive/arduino-uno.md +++ /dev/null @@ -1,82 +0,0 @@ ---- -title: How to configure ATmega328P microcontrollers to run at 3.3V and 5V -date: 2025-04-10 -layout: post ---- - -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. - -<table style="border: none; width: 100%;"> - <tr style="border: none;"> - <td style="border: none; width: 50%; vertical-align: top;"> - <img src="pinout.png" alt="Pinout" style="width: 100%"> - <p style="text-align: center;">Pinout</p> - </td> - <td style="border: none; width: 50%; vertical-align: top;"> - <img src="breadboard.jpeg" alt="Circuit" style="width: 100%"> - <p style="text-align: center;">Breadboard</p> - </td> - </tr> -</table> - -## 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](Makefile) 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 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. - -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](3v3.Makefile) 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 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. - |
