Problem Programming PIC18F2550

[dmitri]

One more question on PIC18F2550. Is it supposed to be recognized by the OS right after it's flashed, even if ATMega and optocoupler IC are not in their sockets and nothing else is connected to the digital board (keyboard, LCD, etc.)?

Yes, it should be recognised without anything else connected.

[Firelord]

Yes, it should be recognised without anything else connected.

All right, thanks. If I succeed in resolving this issue I will report back.

[dmitri]

Does it at least say that something was connected to the USB port but is no recognised?

[Firelord]

Does it at least say that something was connected to the USB port but is no recognised?

Absolutely nothing happens (tried connecting the board to two PCs). Checked the USB cable and also short/break defects on the board, and it all seems correct.

[Firelord]

I'm not quite sure whether it's relevant or not (this was discussed earlier in this topic) -- between the VUSB of the PIC (pin 14) and the ground I get 1.38V.

[dmitri]

Check voltage on pins 1, 8, 14, 19, 20 and 26.

[Firelord]

Here are the measurements. Pins 8, 19 and 26 are connected to the ground, so hopefully you want a reading between those pins and VBUS of the USB.

1: 4.97V
8: gnd, 4.96V
14: 1.38V
19: gnd, 4.96V
20: 4.97V
26: gnd, 4.94V

[dmitri]

Here are the measurements. Pins 8, 19 and 26 are connected to the ground, so hopefully you want a reading between those pins and VBUS of the USB.

No, I wanted to see that they are properly grounded and that they read 0V exactly.

1: 4.97V
8: gnd, 4.96V

8 Must be 0V.

14: 1.38V

14 must be 3.3V. If it's not then either PIC is not properly grounded or some of the pins are shorted to ground/Vcc. If neither then PIC or the crystal is faulty/damaged.

19: gnd, 4.96V

19 must be 0V.

20: 4.97V
26: gnd, 4.94V

26 must be 0V.

[Firelord]

No, I wanted to see that they are properly grounded and that they read 0V exactly.

They read 0V of course.

So I'll start dealing with pin 14 then. Maybe check the caps around it and replace the crystal for one thing. If this doesn't help I'll order another PIC. By the way, what should the reading be on pin 14 WITHOUT the PIC in the socket?

[dmitri]

By the way, what should the reading be on pin 14 WITHOUT the PIC in the socket?

No reading, it is not connected to anything in this case and so consequently you should read infinite resistance between this pin and any other point/pin when PIC is out.