RTOS/CC2640: BLE connection failed once system_printf enabled

Tool/software: TI-RTOS

I try to use System_printf() to print message to Console on debugger.

Currently setup :

• Using CC2650 Lauchpad XDS-110 connect to external CC2640 
• Using C:\ti\simplelink\ble_sdk_2_02_01_18\examples\cc2650lp\simple_peripheral\ccs\app
• Using CCS V7

I following info from forum and doc.  Had done following :

• In CCS project : TOOLS --> appl_ble.cfg

var SysStd = xdc.useModule('xdc.runtime.SysStd');
var System = xdc.useModule('xdc.runtime.System');

System.SupportProxy = SysStd;

• In c file

#include <xdc/runtime/System.h>

#define DELAY_MS(i) (Task_sleep(((i) * 1000) / Clock_tickPeriod))

static void sensorDeviceTaskFxn(UArg a0, UArg a1)
{

while(1)

{

DELAY_MS(1000);

System_printf("Device Task Running");}

}

}

Once I enable the code to print once a second, the BLE connection will fail.  If I remove the debug print, the simple_peripheral will work just fine.

Thanks for your advice.