关于dsp28335的串口通信与PWM发生波形的问题

error #10234-D: unresolved symbols remain

error #10010: errors encountered during linking; "Example24_DSP2833x_SCI_echoback.out" not built
main.c文件代码如下:

#include "DSP2833x_Device.h"     // DSP2833x Headerfile Include File
#include "DSP2833x_Examples.h"   // DSP2833x Examples Include File

#include "leds.h"
#include "time.h"
#include "uart.h"
#include "epwm.h"
void main()
{
//Uint16 ReceivedChar=0;
InitSysCtrl();
InitPieCtrl();
IER = 0x0000;
IFR = 0x0000;
InitPieVectTable();
LED_Init();
TIM0_Init(150,200000);//200ms
UARTa_Init(1152000);
send_init();
while(1)
{
send_data();
DELAY_US(1000);
}
}