Improve writing.

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.