MSP430提供的USB官方例程里有一句语法看不懂？求指教！！！里面时钟具体是怎么配置的？我只看见一句话USBHAL_initClocks(8000000); // Config clocks. MCLK=SMCLK=FLL=8MHz; ACLK=REFO=32kHz，这句话如何理解？？？
具体程序例程见下面：
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/*
* ======== main.c ========
* "Simple Send"
*
* This example shows a very simplified way of sending. This might be used in
* an application where the main functionality doesn't change much if a USB
* host is present or not. It simply calls USBCDC_sendDataInBackground(); if no
* host is present, it simply carries on.
*
* Simply build, run, and attach to a USB host. Run a terminal application
* and open the COM port associated with this device. (In Windows, check the
* Device Manager.) The time should be displayed, every second.
*
* Note that this code is identical to example H9, except for one line of
* code: the call to USBCDC_sendDataInBackground() instead of
* USBHID_sendDataInBackground(). This reflects the symmetry between writing
* MSP430 code for CDC vs. HID-Datapipe.
*
*+----------------------------------------------------------------------------+
* Please refer to the MSP430 USB API Stack Programmer's Guide, located
* in the root directory of this installation for more details.
* ---------------------------------------------------------------------------*/
#include <string.h>
#include "driverlib.h"
#include "USB_config/descriptors.h"
#include "USB_API/USB_Common/device.h"
#include "USB_API/USB_Common/usb.h" //USB-specific functions
#include "USB_API/USB_CDC_API/UsbCdc.h"
#include "USB_app/usbConstructs.h"
/*
* NOTE: Modify hal.h to select a specific evaluation board and customize for
* your own board.
*/
#include "hal.h"
// Function declarations
void convertTimeBinToASCII(uint8_t* timeStr);
void initRTC(void);
// Application globals
volatile uint8_t hour = 4, min = 30, sec = 00; // Real-time clock (RTC) values. 4:30:00
volatile uint8_t bSendTimeToHost = FALSE; // RTC-->main(): "send the time over USB"
uint8_t timeStr[9]; // Stores the time as an ASCII string
/*
* ======== main ========
*/
void main(void)
{
WDT_A_hold(WDT_A_BASE); //Stop watchdog timer
// Minimum Vcore setting required for the USB API is PMM_CORE_LEVEL_2
PMM_setVCore(PMM_CORE_LEVEL_2);
USBHAL_initPorts(); // Config GPIOS for low-power (output low)
USBHAL_initClocks(8000000); // Config clocks. MCLK=SMCLK=FLL=8MHz; ACLK=REFO=32kHz
USB_setup(TRUE,TRUE); // Init USB & events; if a host is present, connect
initRTC(); // Start the real-time clock
__enable_interrupt(); // Enable interrupts globally
while (1)
{
// Enter LPM0, which keeps the DCO/FLL active but shuts off the
// CPU. For USB, you can't go below LPM0!
__bis_SR_register(LPM0_bits + GIE);
// If USB is present, sent the time to the host. Flag is set every sec
if (bSendTimeToHost)
{
bSendTimeToHost = FALSE;
convertTimeBinToASCII(timeStr);
// This function begins the USB send operation, and immediately
// returns, while the sending happens in the background.
// Send timeStr, 9 bytes, to intf #0 (which is enumerated as a
// COM port). 1000 retries. (Retries will be attempted if the
// previous send hasn't completed yet). If the bus isn't present,
// it simply returns and does nothing.
if (USBCDC_sendDataInBackground(timeStr, 9, CDC0_INTFNUM, 1000))
{
_NOP(); // If it fails, it'll end up here. Could happen if
// the cable was detached after the connectionState()
} // check, or if somehow the retries failed
}
} //while(1)
} //main()
// Starts a real-time clock on TimerA_0. Earlier we assigned ACLK to be driven
// by the REFO, at 32768Hz. So below we set the timer to count up to 32768 and
// roll over; and generate an interrupt when it rolls over.
void initRTC(void)
{
TA0CCR0 = 32768;
TA0CTL = TASSEL_1+MC_1+TACLR; // ACLK, count to CCR0 then roll, clear TAR
TA0CCTL0 = CCIE; // Gen int at rollover (TIMER0_A0 vector)
}
// Timer0 A0 interrupt service routine. Generated when TimerA_0 (real-time
// clock) rolls over from 32768 to 0, every second.
#if defined(__TI_COMPILER_VERSION__) || (__IAR_SYSTEMS_ICC__)
#pragma vector=TIMER0_A0_VECTOR
__interrupt void TIMER0_A0_ISR (void)
#elif defined(__GNUC__) && (__MSP430__)
void __attribute__ ((interrupt(TIMER0_A0_VECTOR))) TIMER0_A0_ISR (void)
#else
#error Compiler not found!
#endif
{
if (sec++ == 60)
{
sec = 0;
if (min++ == 60)
{
min = 0;
if (hour++ == 24)
{
hour = 0;
}
}
}
bSendTimeToHost = TRUE; // Time to update
__bic_SR_register_on_exit(LPM3_bits); // Exit LPM
}
// Convert a number 'bin' of value 0-99 into its ASCII equivalent. Assumes
// str is a two-byte array.
void convertTwoDigBinToASCII(uint8_t bin, uint8_t* str)
{
str[0] = '0';
if (bin >= 10)
{
str[0] = (bin / 10) + 48;
}
str[1] = (bin % 10) + 48;
}
// Convert the binary globals hour/min/sec into a string, of format "hr:mn:sc"
// Assumes str is an nine-byte string.
void convertTimeBinToASCII(uint8_t* str)
{
uint8_t hourStr[2], minStr[2], secStr[2];
convertTwoDigBinToASCII(hour, hourStr);
convertTwoDigBinToASCII(min, minStr);
convertTwoDigBinToASCII(sec, secStr);
str[0] = hourStr[0];
str[1] = hourStr[1];
str[2] = ':';
str[3] = minStr[0];
str[4] = minStr[1];
str[5] = ':';
str[6] = secStr[0];
str[7] = secStr[1];
str[8] = '\n';
}
/*
* ======== UNMI_ISR ========
*/
#if defined(__TI_COMPILER_VERSION__) || (__IAR_SYSTEMS_ICC__)
#pragma vector = UNMI_VECTOR
__interrupt void UNMI_ISR (void)
#elif defined(__GNUC__) && (__MSP430__)
void __attribute__ ((interrupt(UNMI_VECTOR))) UNMI_ISR (void)
#else
#error Compiler not found!
#endif
{
switch (__even_in_range(SYSUNIV, SYSUNIV_BUSIFG )) {
case SYSUNIV_NONE:
__no_operation();
break;
case SYSUNIV_NMIIFG:
__no_operation();
break;
case SYSUNIV_OFIFG:
UCS_clearFaultFlag(UCS_XT2OFFG);
UCS_clearFaultFlag(UCS_DCOFFG);
SFR_clearInterrupt(SFR_OSCILLATOR_FAULT_INTERRUPT);
break;
case SYSUNIV_ACCVIFG:
__no_operation();
break;
case SYSUNIV_BUSIFG:
// If the CPU accesses USB memory while the USB module is
// suspended, a "bus error" can occur. This generates an NMI. If
// USB is automatically disconnecting in your software, set a
// breakpoint here and see if execution hits it. See the
// Programmer's Guide for more information.
SYSBERRIV = 0; // Clear bus error flag
USB_disable(); // Disable
}
}
//Released_Version_5_00_01 |
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