diff options
Diffstat (limited to '_archive/arduino-uno.md')
| -rw-r--r-- | _archive/arduino-uno.md | 45 |
1 files changed, 27 insertions, 18 deletions
diff --git a/_archive/arduino-uno.md b/_archive/arduino-uno.md index 99e3985..41407c3 100644 --- a/_archive/arduino-uno.md +++ b/_archive/arduino-uno.md @@ -1,16 +1,16 @@ --- -title: Programming ATmega328P chips +title: ATmega328P chips date: 2025-04-10 author: Wickramage Don Sadeep Madurange layout: post --- -This post is a step-by-step guide for wiring up ATmega328P ICs to run at 5V -with a 16MHz crystal and 3.3V with an 8MHz crystal. While the 5V -configuration is common, the 3.3V configuration can be advantageous in -low-power applications and when interfacing with parts that run at 3.3V. - -## 5V-16MHz configuration +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. @@ -27,40 +27,49 @@ The steps that follow refer to the following pinout. </tr> </table> +## 5V-16MHz configuration + 1. Connect pin 1 to 5V via a 10kΩ resistor. 2. Connect a 16MHz crystal oscillator across pins 9 and 10. 3. Connect each pin of the crystal to ground via 22pF capacitors. 4. Connect pins 7, 20, and 21 to 5V. 5. Connect pins 8 and 22 to ground. -In addition to the connections described above, it's a good idea to add 0.1μF +In addition to the the connections above, 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 avr-gcc and avrdude. ## 3.3V-8MHz 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 3.3V supply. +Standard ATmega328P chips are preconfigured to run at 5V. To run one at 3.3V, +we must first modify its fuses (e.g., BOD level). If the chip contains a +pre-installed bootloader that expects a 16MHz clock (such as the Arduino Uno +bootloader), it must be replaced with one that is more amenable to an 8MHz +clock. + +In the following steps, we use an Arduino Uno as an in-system programmer to +replace the embedded bootloader and modify the appropriate fuses. - 1. Upload the 'ArduinoISP' sketch to the Uno. - 2. Wire up the ATmega328P as described in the previous section. Replace the 5V - supply with a 3.3V supply and use an 8MHz crystal instead of the 16MHz + 1. Upload the 'ArduinoISP' sketch to the Arduino Uno. + 2. Wire up the ATmega328P IC as described in the previous section, while + replacing the 5V supply with a 3.3V supply and 16MHz crystal with an 8MHz crystal. 3. Connect the SPI ports (SCK, MISO, and MOSI) of the two MCUs. - 4. Connect Uno's SS pin to the IC's pin 1 (RESET). - 5. The IC can be powered by the Arduino Uno's 5V pin. + 4. Connect the Arduino Uno's SS pin to the IC's RESET pin (pin 1). + 5. Connect the IC's V<sub>CC</sub> to a 5V supply (e.g., the Arduino Uno's 5V + pin). 6. Burn the bootloader to the ATmega328P: - Select 'ATmega328P (3.3V, 8MHz)' from Tools > Processor. - Select 'Arduino as ISP' from Tools > Programmer. - Select Tools > Burn Bootloader. The ATmega328P is now ready to run at 8MHz with a 3.3V power supply. You can -upload programs to the ATmega328P as you usually would using avrdude. +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. 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 ADC -Voltage Reference in the datasheet for more information. +not connect AREF (pin 21) to V<sub>cc</sub>. Refer to section 23.5.2 in the +datasheet for more information. |