Strange SerOut Problem

[masosi]

This graph...
Correct?

[skimask]

This graph...
Correct?

That -1% @ 5v isn't going to kill your serial.
Also, it's say 'TYPICAL'...doesn't really mean 'yours'.

[masosi]

Ah... well thats another desperate idea gone...

I'll try the timing trials.

[masosi]

I've tried the circuit with the Crystal (4MHz), everything seems to be the same...

Attached is the circuit diagram, could someone please check it to see what I am doing wrong please???

The LED blinks if the serial port is not connected to the computer.
The LED doesn't blink if the serial port IS connected to the computer, so I'm thinking its a grounding problem. Any suggestions?

This is the code that I am testing with:

PORTA = 0
PORTB = 0
CMCON = 7 'Set 16F628A Comparators off

Include "modedefs.bas"
light var PORTB.0
Low light

Start:
Toggle light
SerOut PORTA.1,N300,["Pulse",10,13]
Pause 100
goto Start

High light
end

[skimask]

I've tried the circuit with the Crystal (4MHz), everything seems to be the same...

Attached is the circuit diagram, could someone please check it to see what I am doing wrong please???

The LED blinks if the serial port is not connected to the computer.
The LED doesn't blink if the serial port IS connected to the computer, so I'm thinking its a grounding problem. Any suggestions?

This is the code that I am testing with:

PORTA = 0
PORTB = 0
CMCON = 7 'Set 16F628A Comparators off

Include "modedefs.bas"
light var PORTB.0
Low light

Start:
Toggle light
SerOut PORTA.1,N300,["Pulse",10,13]
Pause 100
goto Start

High light
end

Ya, there's a few things wrong with that.
Check your little green book...page 131, 136, 139, 144. You might find your problem/answer there.

[paul borgmeier]

You show VSS = -5V on your sketch. It should be VSS = 0V

ALso, If you have nothing between your +5.0V power supply and your PIC, then you should measure +5.0V between VDD and VSS on your PIC (not 3.5V).

EDIT: it sounds like a grounding problem just like you suspected

[masosi]

You show VSS = -5V on your sketch. It should be VSS = 0V

ALso, If you have nothing between your +5.0V power supply and your PIC, then you should measure +5.0V between VDD and VSS on your PIC (not 3.5V).

EDIT: it sounds like a grounding problem just like you suspected

Well by -5V, I mean the negative side of the power supply.
This is the power supply I'm using (pretty cheap and nasty, but I thought it would do the job (it did for a while)).
http://www.jaycar.com.au/productView...Max=&SUBCATID= - Model MP-3144 (the first one listed).
...I don't know what switchmode means...

[masosi]

I've tried with and without a resistor on the Rx and Tx Pin, there's no difference.

Does it make sense that the serial port seems to be sucking the life out of the circuit...?

[skimask]

I've tried with and without a resistor on the Rx and Tx Pin, there's no difference.

Does it make sense that the serial port seems to be sucking the life out of the circuit...?

No, but it makes sense that without the resistor, you probably smoked all of your ports.

But...back to the timing thing. The LED blinks, ok... Back to basics...
Do you have an LCD? Make a counter, one second, power up the PIC, start your stopwatch. Wait for 100 seconds. If your watch and the PIC/LCD match up after 100 seconds, you can be reasonably sure you're within 1-2% of the 4Mhz clock speed. The longer you go, the more accurately you can count it up.