How to set up PWM frequency

[DS-567]

I can't figure out how to set a PWM frequency of any value between 10kHz and 20kHz using the neorv32_pwm_setup() function.

Note I am using an old version of Neorv32 that only accepts one parameter as input to this function, i.e. the clock prescaler 3-bits.

I can achieve 6.1kHz with the prescaler_64 and the next prescaler jumps to 48kHz. How can I achieve programmable PWM frequency?

[stnolting]

With the old version (before v1.10.5.4 / #1049), the PWM frequency could only be configured via the 3-bit clock divider - which only allowed a very limited spectrum:

neorv32/sw/lib/include/neorv32.h

Lines 210 to 219 in a9a8e20

	enum NEORV32_CLOCK_PRSC_enum {
	CLK_PRSC_2 = 0, /**< CPU_CLK / 2 */
	CLK_PRSC_4 = 1, /**< CPU_CLK / 4 */
	CLK_PRSC_8 = 2, /**< CPU_CLK / 8 */
	CLK_PRSC_64 = 3, /**< CPU_CLK / 64 */
	CLK_PRSC_128 = 4, /**< CPU_CLK / 128 */
	CLK_PRSC_1024 = 5, /**< CPU_CLK / 1024 */
	CLK_PRSC_2048 = 6, /**< CPU_CLK / 2048 */
	CLK_PRSC_4096 = 7 /**< CPU_CLK / 4096 */
	};

This is precisely why the PWM module has been revised and now offers far more options for setting the PWM frequency.

[DS-567]

Ah right that makes sense, thanks Stephan.

Any hacks or workarounds? 😅

[stnolting]

Oh, that's complicated... The easiest “hack” would be to upgrade to the latest version. 😅

[DS-567]

Haha, I might have to. Thanks anyway Stephan 👍