refactor(PWM):

Modified for a more space optimised PWM function

lab_4/lab_4.c

@@ -15,8 +15,6 @@
 #include "hardware/adc.h"
 
 #define PWM_PIN 2
-#define PWM_FREQ 20
-#define PWM_DUTY 50
 
 #define ADC_PIN 26
 #define ADC_FREQ 25
@@ -41,48 +39,6 @@ bool repeating_timer_callback (struct repeating_timer *t) {
     return true;
 }
 
-/**
- * Helper function to calculate the clock divider and wrap value for PWM
- * Based on: https://www.i-programmer.info/programming/hardware/14849-the-pico-in-c-basic-pwm.html
- *
- * RP2040 clock is 125 MHz, PWM Counter is 16-bit
- * Clock divider is 16-bit, with 12-bit integer and 4-bit fraction
- * @param slice_num     PWM slice number
- * @param channel       PWM channel
- * @param frequency     PWM frequency
- * @param duty_cycle    PWM duty cycle
- * @return              PWM wrap value
- */
-uint32_t pwm_set_freq_duty (uint slice_num,
-                            uint channel, uint32_t frequency, int duty_cycle) {
-    uint32_t clock = 125000000;
-
-    // divider = Ceil(16 * clock / 65536 * frequency) + remainder
-    //         = Ceil(clock / frequency / 4096) + remainder
-    uint32_t divider16 = clock / frequency / 4096 +
-                         (clock % (frequency * 4096) !=
-                          0); // Round up if less than 1
-
-    // If divider is less than 16, set it to 16 (16-bit counter)
-    if (divider16 / 16 == 0)
-    {
-        divider16 = 16;
-    }
-
-    // Wrap value is 16 bits, so max value is 65535 (2^16 - 1)
-    uint32_t wrap = clock * 16 / divider16 / frequency - 1;
-
-    // Set clock divider and wrap value
-    pwm_set_clkdiv_int_frac(slice_num, divider16 / 16,
-                            divider16 & 0xF);
-    pwm_set_wrap(slice_num, wrap);
-
-    // Level = wrap * duty_cycle(as fraction)
-    //       = wrap * duty_cycle / 100
-    pwm_set_chan_level(slice_num, channel, wrap * duty_cycle / 100);
-    return wrap;
-}
-
 /**
  * Setup Function for PWM and ADC
  * @param timer   Repeating timer for ADC
@@ -92,7 +48,11 @@ void setup (struct repeating_timer *timer) {
     gpio_set_function(PWM_PIN, GPIO_FUNC_PWM);
     uint slice_num = pwm_gpio_to_slice_num(PWM_PIN);
     uint channel = pwm_gpio_to_channel(PWM_PIN);
-    pwm_set_freq_duty(slice_num, channel, PWM_FREQ, PWM_DUTY);
+
+    pwm_set_clkdiv(slice_num, 100); // 125 MHz / 100 = 1.25 MHz
+    pwm_set_wrap(slice_num, 62500); // 1.25 MHz / 62500 = 20 Hz
+    pwm_set_chan_level(slice_num, channel, 62500/2); // 50% duty cycle
+
     pwm_set_enabled(slice_num, true);
 
     // ADC setup