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Added USB clock set up + corrected OSC->CR defines 

Added USB clock set divider up for 48MHz operation, corrected oscillator MCU loading capacitor defines.
External capacitors not fitted to the Teensy3.1 PCB.
USBSerial tested using official Hello World program for serial communication to pc terminal.
pull/957/head
Paul Staron 2015-03-07 22:59:07 +00:00
parent 2dfb1b743f
commit 256321199f
1 changed files with 4 additions and 2 deletions
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6
libraries/mbed/targets/cmsis/TARGET_Freescale/TARGET_K20XX/TARGET_TEENSY3_1/system_MK20DX256.c
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@ -202,9 +202,11 @@ void SystemInit (void) {
#elif (CLOCK_SETUP == 3)
/* SIM->CLKDIV1: OUTDIV1=0,OUTDIV2=0,OUTDIV3=1,OUTDIV4=1,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0,??=0 */
SIM->CLKDIV1 = (uint32_t)0x00110000u; /* Update system prescalers */
/* SIM->CLKDIV2: USBDIV=5,USBFRAC=0 */
SIM->CLKDIV2 = (uint32_t)0x05u; /* Divide 72MHz system clock for USB 48MHz */
/* Switch to FBE Mode */
/* OSC0->CR: ERCLKEN=0,??=0,EREFSTEN=0,??=0,SC2P=0,SC4P=0,SC8P=0,SC16P=0 */
OSC0->CR = (uint8_t)0x0Au; // this is required if there are no external capacitors fitted to the Xtal
/* OSC0->CR: ERCLKEN=0,??=0,EREFSTEN=0,??=0,SC2P=1,SC4P=0,SC8P=1,SC16P=0 */
OSC0->CR = OSC_CR_SC8P_MASK | OSC_CR_SC2P_MASK; /* 10pF loading capacitors for 16MHz system oscillator*/
/* MCG->C7: OSCSEL=0 */
MCG->C7 = (uint8_t)0x00u;
/* MCG->C2: ??=0,??=0,RANGE0=2,HGO=0,EREFS=1,LP=0,IRCS=0 */