From 8cd867cd53794386cb9443bfc023fe97c5c5fa47 Mon Sep 17 00:00:00 2001 From: Sadeep Madurange Date: Sat, 25 Oct 2025 18:19:48 +0800 Subject: Render posts. --- _site/archive/arduino-uno/index.html | 117 +++++++++++++++++++++++++++++++++++ 1 file changed, 117 insertions(+) create mode 100644 _site/archive/arduino-uno/index.html (limited to '_site/archive/arduino-uno/index.html') diff --git a/_site/archive/arduino-uno/index.html b/_site/archive/arduino-uno/index.html new file mode 100644 index 0000000..ff3ca44 --- /dev/null +++ b/_site/archive/arduino-uno/index.html @@ -0,0 +1,117 @@ + + + + + Notes on programming ATmega328P chips + + + Notes on programming ATmega328P chips + + + + + + + + + +
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NOTES ON PROGRAMMING ATMEGA328P CHIPS

+ +
10 APRIL 2025
+ +
+ +

This post is a step-by-step guide for wiring up ATmega328P ICs to run at 5 V +with a 16 MHz crystal and 3.3 V with an 8 MHz crystal. While the 5 V +configuration is common, the 3.3 V configuration can be advantageous in +low-power applications and when interfacing with parts that run at 3.3 V.

+ +

5 V - 16 MHz configuration

+ +

The steps that follow refer to the following pinout.

+ + + + + + +
+ Pinout +

Pinout

+ 		+ Circuit +

Breadboard

+
+ +
    +
  1. Connect pin 1 to 5 V via a 10 kΩ resistor.
    2. +
  2. Connect a 16 MHz crystal oscillator across pins 9 and 10.
    3. +
  3. Connect each pin of the crystal to ground via 22 pF capacitors.
    4. +
  4. Connect pins 7, 20, and 21 to 5 V.
    5. +
  5. Connect pins 8 and 22 to ground.
    6. +
+ +

In addition to the connections described above, it’s a good idea to add 0.1 μF +decoupling capacitors between pins 7, 20, and 21 and ground. +Here’s a sample Makefile for avr-gcc and avrdude.

+ +

3.3 V - 8 MHz configuration

+ +

The following steps use Arduino Uno as an ISP and Arduino utilities to program +ATmega328P’s bootloader and the fuses (e.g., BOD level) for a 3.3 V supply.

+ +
    +
  1. Upload the ‘ArduinoISP’ sketch to the Uno.
    2. +
  2. Wire up the ATmega328P as described in the previous section. Replace the 5 V +supply with a 3.3 V supply and use an 8 MHz crystal instead of the 16 MHz +crystal.
    3. +
  3. Connect the SPI ports (SCK, MISO, and MOSI) of the two MCUs.
    4. +
  4. Connect Uno’s SS pin to the IC’s pin 1 (RESET).
    5. +
  5. The IC can be powered by the Arduino Uno’s 5 V pin.
    6. +
  6. Burn the bootloader to the ATmega328P: +
      +
    • Select ‘ATmega328P (3.3 V, 8 MHz)’ from Tools > Processor.
      • +
    • Select ‘Arduino as ISP’ from Tools > Programmer.
      • +
    • Select Tools > Burn Bootloader.
      • +
    +
    7. +
+ +

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

+ +

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

+ +
+ +

by W. D. Sadeep Madurange

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