Possible Causes for Power on problem

Hi

Hv created a prototype on a breadboard involving a PIC MCU, a matrix keypad, LCD, buzzer that runs off 3xAA battery. Everytime I turn on the switch, it will display a menu of items which I then select using the keypad.

Quite frequently however, I notice that whenever I turn on the switch, nothing appears on the LCD. I have to turn off and on, sometimes more than once before I see the menu.

Any idea why this is so?

Thks!

Perhaps you're not waiting long enough for the LCD to initialise?.

i agree with Nigel. This problem hit me a while back and it was indeed in the delay for initialization. I suggest you set it to delay a bit longer if anything. If that doesnt work then i suggest you post more info like schematic/code. So we can see what it is. (or try at least )

You might also try enabling the POR (Power On Reset) fuse in your config' settings...

Mike

The LCD delay should have been sufficient, but I'll try again.

Couldn't find the POR setting; I'm using a 18F4620. However, just found out there is a setting PWRT, "power-up" timer, which provides a 65 ms (nominal) delay from the time the PIC detects that it has been powered up until program code begins execution. This delay allows the device's power supply to stabilize.

Sorry I couldn't do the above testings as I am in the middle of some escalation at work. So will report later to see if any of your suggestions work when I have the opportunity to try them out. Thks!

Not sure if you are using a Internal oscillator but if so be sure to wait for:

IOFS: INTOSC Frequency Stable bit.

How about posting some code if possible.

Urahara said:

Couldn't find the POR setting; I'm using a 18F4620.

Click to expand...

Sorry, I meant the BOR (brown out reset)...

Mike