LED Blink is not working but code can program with PIC18F4550 and MikroC

Question

I tried to code LED on-off program for test PIC18F4550 microcontroller. The code can program to IC using Pikkit 2 but a program is not working. I code by using MikroC Pro for Pic 6.6.1. I am using 4Mhz crystal oscillator.

Why program is not working? is it IC not working?

Code:

void main() {
  TRISA.B0=0;

  while(1){
     PORTA.B0=1;
     Delay_ms(2000);
     PORTA.B0=0;
     Delay_ms(2000);
  }

}

This is my circuit diagram:

Answer 1

TRIS are the registers that control the direction (input or output) of a pin. You use only this register, so all you are doing is toggling between input and output.

The first line is correct, but in the loop you must use a PORT or (better) LAT register to toggle the pin between high and low.

Answer 2

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. LED orientations that work.

If the diode in your schematic is the LED in question then it is missing the "light" arrows from the symbol and it is in backwards so it will never light.

^{simulate this circuit}

Figure 2. This RC addition causes the \$ \overline {\text {MCLR}} \$ line to follow the power supply with a 10k x 100n = 1 ms time delay.

Also the \$ \overline {\text {MCLR}} \$ may need to be pulled high a little later after the chip has powered up. A small RC time delay is normally used for this. Check the datasheet examples for recommended values. The delay allows the internal voltages to settle and holding the line low resets everything to known initial conditions ensuring proper initialisation.