Make all float->int/frac conversions round to nearest by default

src/rp2040/pico_platform/include/pico/platform.h

@@ -70,6 +70,11 @@
 #define PICO_RAM_VECTOR_TABLE_SIZE (VTABLE_FIRST_IRQ + NUM_IRQS)
 #endif
 
+// PICO_CONFIG: PICO_CLKDIV_ROUND_NEAREST, True if floating point clock divisors should be rounded to the nearest possible clock divisor by default rather than rounding down, type=bool, default=1, group=pico_platform
+#ifndef PICO_CLKDIV_ROUND_NEAREST
+#define PICO_CLKDIV_ROUND_NEAREST 1
+#endif
+
 #ifndef __ASSEMBLER__
 
 /*! \brief No-op function for the body of tight loops

src/rp2350/pico_platform/include/pico/platform.h

@@ -63,6 +63,11 @@
 #define PICO_USE_STACK_GUARDS 0
 #endif
 
+// PICO_CONFIG: PICO_CLKDIV_ROUND_NEAREST, True if floating point clock divisors should be rounded to the nearest possible clock divisor by default rather than rounding down, type=bool, default=1, group=pico_platform
+#ifndef PICO_CLKDIV_ROUND_NEAREST
+#define PICO_CLKDIV_ROUND_NEAREST 1
+#endif
+
 #ifndef __ASSEMBLER__
 
 /*! \brief No-op function for the body of tight loops

src/rp2_common/hardware_adc/include/hardware/adc.h

@@ -70,6 +70,11 @@
 #define ADC_TEMPERATURE_CHANNEL_NUM (NUM_ADC_CHANNELS - 1)
 #endif
 
+// PICO_CONFIG: PICO_ADC_CLKDIV_ROUND_NEAREST, True if floating point ADC clock divisors should be rounded to the nearest possible clock divisor rather than rounding down, type=bool, default=PICO_CLKDIV_ROUND_NEAREST, group=hardware_adc
+#ifndef PICO_ADC_CLKDIV_ROUND_NEAREST
+#define PICO_ADC_CLKDIV_ROUND_NEAREST PICO_CLKDIV_ROUND_NEAREST
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -198,6 +203,9 @@ static inline void adc_run(bool run) {
  */
 static inline void adc_set_clkdiv(float clkdiv) {
     invalid_params_if(HARDWARE_ADC, clkdiv >= 1 << (ADC_DIV_INT_MSB - ADC_DIV_INT_LSB + 1));
+#if PICO_ADC_CLKDIV_ROUND_NEAREST
+    clkdiv += 0.5f / (1 << ADC_DIV_INT_LSB); // round to the nearest fraction
+#endif
     adc_hw->div = (uint32_t)(clkdiv * (float) (1 << ADC_DIV_INT_LSB));
 }
 

src/rp2_common/hardware_clocks/include/hardware/clocks.h

@@ -253,6 +253,11 @@ extern "C" {
 #else
 #define PARAM_ASSERTIONS_ENABLED_HARDWARE_CLOCKS 0
 #endif
+#endif
+
+ // PICO_CONFIG: PICO_CLOCK_GPIO_CLKDIV_ROUND_NEAREST, True if floating point GPIO clock divisors should be rounded to the nearest possible clock divisor rather than rounding down, type=bool, default=PICO_CLKDIV_ROUND_NEAREST, group=hardware_clocks
+#ifndef PICO_CLOCK_GPIO_CLKDIV_ROUND_NEAREST
+#define PICO_CLOCK_GPIO_CLKDIV_ROUND_NEAREST PICO_CLKDIV_ROUND_NEAREST
 #endif
 
 typedef clock_num_t clock_handle_t;
@@ -387,6 +392,9 @@ static inline void clock_gpio_init_int_frac(uint gpio, uint src, uint32_t div_in
 static inline void clock_gpio_init(uint gpio, uint src, float div)
 {
     uint div_int = (uint)div;
+#if PICO_CLOCK_GPIO_CLKDIV_ROUND_NEAREST
+    div += 0.5f / (1 << (CLOCKS_CLK_GPOUT0_DIV_FRAC_MSB + 1 - CLOCKS_CLK_GPOUT0_DIV_FRAC_LSB)); // round to the nearest fraction
+#endif
 #if CLOCKS_CLK_GPOUT0_DIV_FRAC_MSB - CLOCKS_CLK_GPOUT0_DIV_FRAC_LSB == 15
     uint16_t frac = (uint16_t)((div - (float)div_int) * (1u << 16));
     clock_gpio_init_int_frac16(gpio, src, div_int, frac);

src/rp2_common/hardware_pio/include/hardware/pio.h

@@ -31,6 +31,12 @@
 #define PICO_PIO_VERSION 0
 #endif
 #endif
+
+// PICO_CONFIG: PICO_PIO_CLKDIV_ROUND_NEAREST, True if floating point PIO clock divisors should be rounded to the nearest possible clock divisor rather than rounding down, type=bool, default=PICO_CLKDIV_ROUND_NEAREST, group=hardware_pio
+#ifndef PICO_PIO_CLKDIV_ROUND_NEAREST
+#define PICO_PIO_CLKDIV_ROUND_NEAREST PICO_CLKDIV_ROUND_NEAREST
+#endif
+
 /** \file hardware/pio.h
  *  \defgroup hardware_pio hardware_pio
  *
@@ -488,6 +494,9 @@ static inline void sm_config_set_clkdiv_int_frac(pio_sm_config *c, uint16_t div_
 
 static inline void pio_calculate_clkdiv8_from_float(float div, uint32_t *div_int, uint8_t *div_frac8) {
     valid_params_if(HARDWARE_PIO, div >= 1 && div <= 65536);
+#if PICO_PIO_CLKDIV_ROUND_NEAREST
+    div += 0.5f / 256; // round to the nearest 1/256
+#endif
     *div_int = (uint16_t)div;
     // not a strictly necessary check, but if this changes, then this method should
     // probably no longer be used in favor of one with a larger fraction

src/rp2_common/hardware_pwm/include/hardware/pwm.h

@@ -103,6 +103,11 @@ static_assert(DREQ_PWM_WRAP7 == DREQ_PWM_WRAP0 + 7, "");
 })
 #endif
 
+// PICO_CONFIG: PICO_PWM_CLKDIV_ROUND_NEAREST, True if floating point PWM clock divisors should be rounded to the nearest possible clock divisor rather than rounding down, type=bool, default=PICO_CLKDIV_ROUND_NEAREST, group=hardware_pwm
+#ifndef PICO_PWM_CLKDIV_ROUND_NEAREST
+#define PICO_PWM_CLKDIV_ROUND_NEAREST PICO_CLKDIV_ROUND_NEAREST
+#endif
+
 static inline void check_slice_num_param(__unused uint slice_num) {
     valid_params_if(HARDWARE_PWM, slice_num < NUM_PWM_SLICES);
 }
@@ -155,6 +160,9 @@ static inline void pwm_config_set_phase_correct(pwm_config *c, bool phase_correc
  */
 static inline void pwm_config_set_clkdiv(pwm_config *c, float div) {
     valid_params_if(HARDWARE_PWM, div >= 1.f && div < 256.f);
+#if PICO_PWM_CLKDIV_ROUND_NEAREST
+    div += 0.5f / (1 << PWM_CH0_DIV_INT_LSB); // round to the nearest fraction
+#endif
     c->div = (uint32_t)(div * (float)(1u << PWM_CH0_DIV_INT_LSB));
 }