Increased clock to 96Mhz and implemented initial usb_init routine

The clock setup should be moved into sysinit

scope-teensy/include/arm_cm4.h

@@ -15,7 +15,10 @@
 #define ARM_INTERRUPT_LEVEL_BITS          4
 
 /*Determines the correct IRQ number from a INT value */
-#define IRQ(N) (N - (1 << ARM_INTERRUPT_LEVEL_BITS))
+#define IRQ(N) (N - (1 << ARM_INTERRUPT_LEVEL_BITS))
+
+/*Sets the priority of an interrupt*/
+#define NVIC_SET_PRIORITY(irqnum, priority)  (*((volatile uint8_t *)0xE000E400 + (irqnum)) = (uint8_t)(priority))
 
 /***********************************************************************/
 // function prototypes for arm_cm4.c

scope-teensy/include/common.h

@@ -50,8 +50,8 @@
  *		   72 MHz			    8		   36
  *
  */
-#define PRDIV_VAL			8				/* PLL prescaler */
-#define VDIV_VAL			36				/* PLL multiplier */
+#define PRDIV_VAL			4				/* PLL prescaler */
+#define VDIV_VAL			24				/* PLL multiplier */
 
 /*
  *  Optionally define the system console (one of the UARTs) for serial I/O.

scope-teensy/include/usb.h

@@ -0,0 +1,19 @@
+/**
+ * Header file for my implementation of using the USB peripheral
+ * Kevin Cuzner
+ */
+#ifndef _USB_H_
+#define _USB_H_
+
+/**
+ * Number of USB endpoints
+ * 15 max
+ */
+#define USB_N_ENDPOINTS 0
+
+/**
+ * Initializes the USB module
+ */
+void usb_init(void);
+
+#endif // _USB_H_

scope-teensy/src/main.c

@@ -1,6 +1,7 @@
 #include "common.h"
 #include "arm_cm4.h"
 #include "adc.h"
+#include "usb.h"
 
 #define LED_ON  GPIOC_PSOR=(1<<5)
 #define LED_OFF GPIOC_PCOR=(1<<5)
@@ -38,15 +39,16 @@ int main(void)
     PIT_TCTRL1 |= PIT_TCTRL_TEN_MASK; // start Timer 1
 
     adc_init(8);
+    usb_init();
 
     enable_irq(IRQ(INT_PIT1));
     EnableInterrupts
 
     while(1)
     {
-        LED_ON;
+        LED2_ON;
         for (n = 0; n < s; n++);
-        LED_OFF;
+        LED2_OFF;
         for (n = 0; n < s; n++);
     }
 
@@ -60,10 +62,10 @@ void PIT1_IRQHandler()
     static uint8_t stat = 0;
     if (count == 30)
     {
-        if (stat)
-            LED2_ON;
+        /*if (stat)
+            LED_ON;
         if (!stat)
-            LED2_OFF;
+            LED_OFF;*/
         stat ^= 0x01;
         count = 0;
     }

scope-teensy/src/usb.c

@@ -0,0 +1,101 @@
+#include "usb.h"
+#include "arm_cm4.h"
+
+/**
+ * Descriptor bits struct
+ * See Table 41-4
+ */
+typedef struct {
+    unsigned rsrv0 :6;  //31-26
+    unsigned bc    :10; //25-16
+    unsigned rsrv1 :8;  //15-8
+    unsigned own   :1;  //7
+    unsigned data0 :1;  //6
+    union {             //5-2
+        unsigned tok_pid :4;
+        struct {
+            unsigned keep      :1;
+            unsigned ninc      :1;
+            unsigned dts       :1;
+            unsigned bdt_stall :1;
+        };
+    };
+    unsigned rsrv2 :2;  //1-0
+} bdt_bits_t;
+
+/**
+ * Buffer Descriptor Table entry
+ * There are two entries per direction per endpoint:
+ *   In  Even/Odd
+ *   Out Even/Odd
+ * A bidirectional endpoint would then need 4 entries
+ */
+typedef struct {
+    union {
+        uint32_t desc;
+        bdt_bits_t desc_bits;
+    };
+    void* addr;
+} bdt_t;
+
+// we enforce a max of 15 endpoints (15 + 1 control = 16)
+#if USB_N_ENDPOINTS > 15
+#error Maximum USB endpoints must be <=15
+#endif // USB_N_ENDPOINTS
+
+/**
+ * Buffer descriptor table, aligned to a 512-byte boundary (see linker file)
+ */
+__attribute__ ((section(".usbdescriptortable"), used))
+static bdt_t table[(USB_N_ENDPOINTS + 1)*4]; //max endpoints is 15 + 1 control
+
+void usb_init(void)
+{
+    uint32_t i;
+
+    //reset the buffer descriptors
+    for (i = 0; i < (USB_N_ENDPOINTS + 1) * 4; i++)
+    {
+        table[i].desc = 0;
+        table[i].addr = 0;
+    }
+
+    //1: Select clock source
+    SIM_SOPT2 |= SIM_SOPT2_USBSRC_MASK | SIM_SOPT2_PLLFLLSEL_MASK; //we use MCGPLLCLK divided by USB fractional divider
+    SIM_CLKDIV2 = SIM_CLKDIV2_USBDIV(1);// SIM_CLKDIV2_USBDIV(2) | SIM_CLKDIV2_USBFRAC_MASK; //(USBFRAC + 1)/(USBDIV + 1) = (1 + 1)/(2 + 1) = 2/3 for 72Mhz clock
+
+    //2: Gate USB clock
+    SIM_SCGC4 |= SIM_SCGC4_USBOTG_MASK;
+
+    //3: Software USB module reset
+    USB0_USBTRC0 |= USB_USBTRC0_USBRESET_MASK;
+    while (USB0_USBTRC0 & USB_USBTRC0_USBRESET_MASK);
+
+    //4: Set BDT base registers
+    USB0_BDTPAGE1 = ((uint32_t)table) >> 8;  //bits 15-9
+    USB0_BDTPAGE2 = ((uint32_t)table) >> 16; //bits 23-16
+    USB0_BDTPAGE3 = ((uint32_t)table) >> 24; //bits 31-24
+
+    //5: Clear all ISR flags and enable weak pull downs
+    USB0_ISTAT = 0xFF;
+    USB0_ERRSTAT = 0xFF;
+    USB0_OTGISTAT = 0xFF;
+    USB0_USBTRC0 |= 0x40; //a hint was given that this is an undocumented interrupt bit
+
+    //6: Enable USB reset interrupt
+    USB0_CTL = USB_CTL_USBENSOFEN_MASK;
+    USB0_USBCTRL = 0;
+
+    USB0_INTEN |= USB_INTEN_USBRSTEN_MASK;
+    //NVIC_SET_PRIORITY(IRQ(INT_USB0), 112);
+    enable_irq(IRQ(INT_USB0));
+
+    //7: Enable pull-up resistor on D+ (Full speed, 12Mbit/s)
+    USB0_CONTROL = USB_CONTROL_DPPULLUPNONOTG_MASK;
+}
+
+void USBOTG_IRQHandler(void)
+{
+    USB0_ISTAT = USB0_ISTAT;
+    GPIOC_PSOR=(1<<5);
+}