pwm

src/SUMMARY.md

@@ -9,5 +9,6 @@
 
 - [Blink LED](./blinky/index.md)
     - [With rp-rs](./blinky/rp-rs.md)
+        - [PWM](./blinky/pwm.md)
     - [With embassy](./blinky/embassy.md)
 - [Resources](./resources.md)

src/blinky/pwm.md

@@ -0,0 +1,55 @@
+
+## What is PWM?
+PWM stands for **Pulse Width Modulation**. It is a technique used to control the amount of power delivered to a device by adjusting the width of the pulses in a signal.
+
+In PWM, a digital signal switches between **on** and **off** states at a high frequency. The **duty cycle** of the signal determines how long it stays on compared to how long it stays off. 
+
+- **Duty Cycle**: The percentage of time the signal is on during one cycle. 
+  - For example:
+    - 100% duty cycle means the signal is always on.
+    - 50% duty cycle means the signal is on half the time and off half the time.
+    - 0% duty cycle means the signal is always off.
+
+In the above example code, we use PWM to fade an LED.
+
+### Fading Up
+The first loop gradually increases the LED brightness from `LOW` (0) to `HIGH` (25,000). The `delay.delay_us(8)` creates a short pause between each increase, allowing the LED to visibly brighten.
+
+### Fading Down
+The second loop decreases the LED brightness back down to `LOW` (0), again using the same delay to make the transition smooth.
+
+### Pause
+After fading up and down, the program pauses for 500 milliseconds before repeating the cycle, allowing the LED to rest briefly.
+
+Play around by adjusting the `delay` and observe. You can even comment out one of the for loop and observe the effect. 
+
+
+## PWM Peripheral in RP2350
+The PWM peripheral is responsible for generating PWM signals. The Pico 2 features 12 PWM generators, known as slices, with each slice having two channels(A/B). This configuration results in a total of 24 PWM output channels available for use.
+
+**Mapping of PWM channels to GPIO Pins**: 
+
+You can find the table on page 1073 of the [RP2350](https://datasheets.raspberrypi.com/rp2350/rp2350-datasheet.pdf) Datasheet for more information. You have to refer this table when using a specific GPIO, as each GPIO corresponds to a particular slice. For instance, using GP25 (for the LED) means you are working with output 4B, which is the B output of the fourth slice.
+
+<img style="display: block; margin: auto;" alt="pico2" src="../images/gpio-map-pwm-channels.png"/>
+
+Initialize the PWM slices by creating an instance using the PAC's PWM peripheral and reset control.
+```rust
+let mut pwm_slices = hal::pwm::Slices::new(pac.PWM, &mut pac.RESETS);
+```
+
+// Retrieve a mutable reference to PWM4 from the initialized PWM slices for further configuration.
+```rust
+let pwm = &mut pwm_slices.pwm4;
+```
+
+// Configure PWM4 to operate in phase-correct mode for smoother output transitions.  (You can refer the [secrets arudion PWM](https://docs.arduino.cc/tutorials/generic/secrets-of-arduino-pwm/) if you want to know what is phase-correct)
+```rust
+pwm.set_ph_correct();
+```
+
+// Get a mutable reference to channel B of PWM4 and direct its output to GPIO pin 25.
+```rust
+let channel = &mut pwm.channel_b;
+channel.output_to(pins.gpio25);
+```

src/blinky/rp-rs.md

@@ -146,27 +146,4 @@ cd pico2-blinky/rprs-blinky
 ## How to Run?
 
 You refer the ["Running The Program"](../running.md) section
-
-## What is PWM?
-PWM stands for **Pulse Width Modulation**. It is a technique used to control the amount of power delivered to a device by adjusting the width of the pulses in a signal.
-
-In PWM, a digital signal switches between **on** and **off** states at a high frequency. The **duty cycle** of the signal determines how long it stays on compared to how long it stays off. 
-
-- **Duty Cycle**: The percentage of time the signal is on during one cycle. 
-  - For example:
-    - 100% duty cycle means the signal is always on.
-    - 50% duty cycle means the signal is on half the time and off half the time.
-    - 0% duty cycle means the signal is always off.
-
-In the above example code, we use PWM to fade an LED.
-
-### Fading Up
-The first loop gradually increases the LED brightness from `LOW` (0) to `HIGH` (25,000). The `delay.delay_us(8)` creates a short pause between each increase, allowing the LED to visibly brighten.
-
-### Fading Down
-The second loop decreases the LED brightness back down to `LOW` (0), again using the same delay to make the transition smooth.
-
-### Pause
-After fading up and down, the program pauses for 500 milliseconds before repeating the cycle, allowing the LED to rest briefly.
-
-Play around by adjusting the `delay` and observe. You can even comment out one of the for loop and observe the effect. 
+