|
对于这个问题,官方的设计的确是不太给力,搞个192MHz主频,这些问题也都迎刃而解了。
大家有兴趣可以尝试多种PLL参数的配置组合。
(为了安全稳定起见,开发板配置的例子采用168MHz主频,开发板外置晶振是8MHz)
==========================================================
下面这种180MHz的主频配置,的确是解决了48MHz频率的产生,但是过程参数PLL_VCO超出了范围
#if 0 /* 外部晶振8MHz, 系统主频 180MHz, USB & SDIO时钟 48M */
/* PLL_VCO = (HSE_VALUE / PLL_M) * PLL_N = 720MHz (超频) 正常值 192-432 */
#define PLL_M 4
#define PLL_N 360
/* USB OTG FS, SDIO and RNG Clock = PLL_VCO / PLLQ = 48MHz */
#define PLL_Q 15
/* SYSCLK = PLL_VCO / PLL_P = 180MHz*/
#define PLL_P 4
#endif
=================================================
#if 1 /* 外部晶振8MHz, 系统主频 180MHz, 但是USB & SDIO时钟 51.4M,非标准时钟,造成USB工作异常 */
/* PLL_VCO = (HSE_VALUE / PLL_M) * PLL_N = 360MHz (超频) 正常值 192-432 */
#define PLL_M 8
#define PLL_N 360
/* USB OTG FS, SDIO and RNG Clock = PLL_VCO / PLLQ = 48MHz */
#define PLL_Q 7
/* SYSCLK = PLL_VCO / PLL_P = 180MHz*/
#define PLL_P 2
#endif
=================================================
#if 0 /* 8M晶振, 系统主频 168M, USB & SDIO时钟 48M */
/* PLL_VCO = (HSE_VALUE / PLL_M) * PLL_N = 336MHz 正常值 192-432 */
#define PLL_M 8
#define PLL_N 336
/* USB OTG FS, SDIO and RNG Clock = PLL_VCO / PLLQ = 48MHz */
#define PLL_Q 7
/* SYSCLK = PLL_VCO / PLL_P = 168MHz*/
#define PLL_P 2
#endif
=================================================
#if 0 /* 8M晶振, 系统主频 192M (超频), USB & SDIO时钟 48M */
/* PLL_VCO = (HSE_VALUE / PLL_M) * PLL_N = 336MHz 正常值 192-432 */
#define PLL_M 8
#define PLL_N 384
/* USB OTG FS, SDIO and RNG Clock = PLL_VCO / PLLQ = 48MHz */
#define PLL_Q 8
/* SYSCLK = PLL_VCO / PLL_P = 192MHz*/
#define PLL_P 2
#endif
|
|