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usb cdc example + PWM cause hardfault error

I run USB virtual com port example on NXP LPC1768 successfully, in Keil environment.

by default, the code is in privileged mode.

for example, I added a single line for accessing PWM peripheral and it causes HardFault error.

Also, I tried 

__SVC

solution but it causes HardFault too.

this is Keil pack installer example and I only added a header and a line about PWM:

#include "cmsis_os.h"
#include "rl_usb.h"

#include "Board_GLCD.h"
#include "GLCD_Config.h"
#include "LPC17xx.h"                    // Device header

extern    GLCD_FONT GLCD_Font_6x8;
extern    GLCD_FONT GLCD_Font_16x24;


int main (void) {

  GLCD_Initialize         ();
  GLCD_SetBackgroundColor (GLCD_COLOR_BLUE);
  GLCD_SetForegroundColor (GLCD_COLOR_WHITE);
  GLCD_ClearScreen        ();
  GLCD_SetFont            (&GLCD_Font_16x24);
  GLCD_DrawString         (0U, 0U*24U, "    USB Device      ");
  GLCD_DrawString         (0U, 1U*24U, "   CDC ACM Class    ");
  GLCD_DrawString         (0U, 2U*24U, " VirtualCOM Example ");
  GLCD_DrawString         (0U, 4U*24U, "   USB <-> UART1    ");
  GLCD_DrawString         (0U, 8U*24U, "  Keil Tools by ARM ");
  GLCD_DrawString         (0U, 9U*24U, "    www.keil.com    ");

  USBD_Initialize         (0U);         // USB Device 0 Initialization
  USBD_Connect            (0U);         // USB Device 0 Connect

    LPC_PWM1->PR = 24;   //PWM causes **hardFault** 

  while (1) {
    osSignalWait (0U, osWaitForever);
  }  
}
Solution

  • This causes by PC USB recognition problem.

    It should solve by trying to off the device for 1 or 2 seconds, and then plug it in again.