CPU Overclocking

Description

Some display functions may be CPU speed intensive and may require overclocking to a higher speed. It should be understood that overclocking places the processor in areas where proper function is not guaranteed. The PicoVGA library allows you to control the overclocking of the processor, according to the desired video mode. The minimum and maximum processor frequency can be specified in the VgaCfg() function. By default, the library allows a range of 120 to 270 MHz. However, it may happen that at higher frequencies the processor will not operate correctly and it may be necessary to lower the upper limit. The searched processor frequency can be set with the set_sys_clock_pll() function.

Functions
bool	vcocalc (u32 reqkhz, u32 input, u32 vcomin, u32 vcomax, bool lowvco, u32 *outkhz, u32 *outvco, u16 *outfbdiv, u8 *outpd1, u8 *outpd2)
	Search PLL setup. More...
bool	FindSysClock (u32 reqkhz, u32 *outkhz, u32 *outvco, u16 *outfbdiv, u8 *outpd1, u8 *outpd2)
	Find PLL generator settings with default parameters. (use set_sys_clock_pll to set sysclock) More...
void __not_in_flash_func()	FlashSpeedSetup (int baud)
	Setting the interface speed for external flash. More...

Function Documentation

vcocalc()

bool vcocalc	(	u32	reqkhz,
		u32	input,
		u32	vcomin,
		u32	vcomax,
		bool	lowvco,
		u32 *	outkhz,
		u32 *	outvco,
		u16 *	outfbdiv,
		u8 *	outpd1,
		u8 *	outpd2
	)

Search PLL setup.

Function for finding the optimal setting of the PLL system clock generator. The function is used to specify the desired output frequency, the input frequency of the crystal (12 MHz in Raspberry Pico), the minimum and maximum frequency of the VCO oscillator. The output is the parameters for setting the PLL oscillator. The function returns True if it was able to find a setting for the exact value of the desired frequency. Otherwise, it searches for the setting for the closest frequency and returns False.

Parameters

reqkhz	Required output frequency in kHz
input	PLL input frequency in kHz (default 12000, or use clock_get_hz(clk_ref)/1000)
vcomin	Minimal VCO frequency in kHz (default 400000)
vcomax	Maximal VCO frequency in kHz (default 1600000)
lowvco	Prefer low VCO (lower power but more jiter)
outkhz	Output achieved frequency in kHz (0=not found)
outvco	Output VCO frequency in kHz
outfbdiv	Output fbdiv (16..320)
outpd1	Output postdiv1 (1..7)
outpd2	Output postdiv2 (1..7)

Returns

True if precise frequency has been found, or near frequency used otherwise.

FindSysClock()

bool FindSysClock	(	u32	reqkhz,
		u32 *	outkhz,
		u32 *	outvco,
		u16 *	outfbdiv,
		u8 *	outpd1,
		u8 *	outpd2
	)

Find PLL generator settings with default parameters. (use set_sys_clock_pll to set sysclock)

Parameters

reqkhz	Required frequency in kHz
outkhz	Output achieved frequency in kHz (0=not found)
outvco	Output VCO frequency in kHz
outfbdiv	Output fbdiv (16..320)
outpd1	Output postdiv1 (1..7)
outpd2	Output postdiv2 (1..7)

Returns

True if precise frequency has been found, or near frequency used otherwise.

FlashSpeedSetup()

void __not_in_flash_func() FlashSpeedSetup

(

int

baud

)

Setting the interface speed for external flash.

Parameters

baud	Flash SSI speed (4 default, <4 faster, >4 slower)