Hello, recently I have done Periph Blinky e.g. from LPCOpen library on MCUxpresso. I am using LPC1769 chip and I have toggled GPIO pin. In my case I have used buzzer pin i.e. Port 3 & Pin 25. Instead of using Timer delay I created a delay function i.e. void delay_ms(unsigned int ms). Here I am attaching the systick.c file. Hope it helps:smileyhappy:!!