Use IRC48M clock for USB when F_CPU is 180 or 216 MHz

teensy3/kinetis.h

@@ -1035,6 +1035,7 @@ enum IRQ_NUMBER_t {
 #define SIM_SOPT2_RMIISRC		((uint32_t)0x00080000)		// 0=external, 1=external 1588
 #define SIM_SOPT2_USBSRC		((uint32_t)0x00040000)		// 0=USB_CLKIN, 1=FFL/PLL
 #define SIM_SOPT2_PLLFLLSEL		((uint32_t)0x00010000)		// 0=FLL, 1=PLL
+#define SIM_SOPT2_IRC48SEL		((uint32_t)0x00030000)		// 0=FLL, 1=PLL
 #define SIM_SOPT2_TRACECLKSEL		((uint32_t)0x00001000)		// 0=MCGOUTCLK, 1=CPU
 #define SIM_SOPT2_PTD7PAD		((uint32_t)0x00000800)		// 0=normal, 1=double drive PTD7
 #define SIM_SOPT2_FBSL(n)		((uint32_t)(((n) & 3) << 8))	// FlexBus security level

teensy3/mk20dx128.c

@@ -891,19 +891,19 @@ void ResetHandler(void)
 	SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(0) | SIM_CLKDIV1_OUTDIV2(3) | SIM_CLKDIV1_OUTDIV4(7);
 	SIM_CLKDIV2 = SIM_CLKDIV2_USBDIV(4);
 #elif F_CPU == 216000000
-	// config divisors: 216 MHz core, 54 MHz bus, 27 MHz flash, USB = not feasible
+	// config divisors: 216 MHz core, 54 MHz bus, 27 MHz flash, USB = IRC48M
 	// TODO: gradual ramp-up for HSRUN mode
 	SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(0) | SIM_CLKDIV1_OUTDIV2(3) | SIM_CLKDIV1_OUTDIV4(7);
-	SIM_CLKDIV2 = SIM_CLKDIV2_USBDIV(8) | SIM_CLKDIV2_USBFRAC;
+	SIM_CLKDIV2 = SIM_CLKDIV2_USBDIV(0);
 #elif F_CPU == 192000000
 	// config divisors: 192 MHz core, 48 MHz bus, 27.4 MHz flash, USB = 192 / 4
 	// TODO: gradual ramp-up for HSRUN mode
 	SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(0) | SIM_CLKDIV1_OUTDIV2(3) | SIM_CLKDIV1_OUTDIV4(6);
 	SIM_CLKDIV2 = SIM_CLKDIV2_USBDIV(3);
 #elif F_CPU == 180000000
-	// config divisors: 180 MHz core, 60 MHz bus, 25.7 MHz flash, USB = not feasible
+	// config divisors: 180 MHz core, 60 MHz bus, 25.7 MHz flash, USB = IRC48M
 	SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(0) | SIM_CLKDIV1_OUTDIV2(2) | SIM_CLKDIV1_OUTDIV4(6);
-	SIM_CLKDIV2 = SIM_CLKDIV2_USBDIV(6) | SIM_CLKDIV2_USBFRAC;
+	SIM_CLKDIV2 = SIM_CLKDIV2_USBDIV(0);
 #elif F_CPU == 168000000
 	// config divisors: 168 MHz core, 56 MHz bus, 28 MHz flash, USB = 168 * 2 / 7
 	SIM_CLKDIV1 = SIM_CLKDIV1_OUTDIV1(0) | SIM_CLKDIV1_OUTDIV2(2) | SIM_CLKDIV1_OUTDIV4(5);
@@ -988,8 +988,11 @@ void ResetHandler(void)
 	// now we're in PEE mode
 	// USB uses PLL clock, trace is CPU clock, CLKOUT=OSCERCLK0
 	#if defined(KINETISK)
-	SIM_SOPT2 = SIM_SOPT2_USBSRC | SIM_SOPT2_PLLFLLSEL | SIM_SOPT2_TRACECLKSEL
-		| SIM_SOPT2_CLKOUTSEL(6);
+	#if F_CPU == 216000000 || F_CPU == 180000000
+	SIM_SOPT2 = SIM_SOPT2_USBSRC | SIM_SOPT2_IRC48SEL | SIM_SOPT2_TRACECLKSEL | SIM_SOPT2_CLKOUTSEL(6);
+	#else
+	SIM_SOPT2 = SIM_SOPT2_USBSRC | SIM_SOPT2_PLLFLLSEL | SIM_SOPT2_TRACECLKSEL | SIM_SOPT2_CLKOUTSEL(6);
+	#endif
 	#elif defined(KINETISL)
 	SIM_SOPT2 = SIM_SOPT2_USBSRC | SIM_SOPT2_PLLFLLSEL | SIM_SOPT2_CLKOUTSEL(6)
 		| SIM_SOPT2_UART0SRC(1) | SIM_SOPT2_TPMSRC(1);