LCD will not start

[JohnPaul]

Ski,
I am still using the same chip PIC16F627A.
I failed the LED test. I hook up an LED to the Ground then in series to 330 ohm Resistor and a cable at the end. I tap the cable to +5V and tested the LED polarity. Then I tap each of the pin. I tried one LED then also tried all of the output pins. Program below.
How could I have damaged my chip? It is new. How could I be certain my chip is damaged before I toss it to the trash can?

LED6 VAR PORTB.0 ' Pin LED Test
TRISB = 0 ' PORT B is output
RPT:
PAUSE 2000 ' WAIT 1 SECOND
LED6 = 1 ' Turn Pin LED ON

PAUSE 2000 ' WAIT 1 SECOND
LED6 = 0 ' Turn Pin LED OFF

GOTO RPT ' Repeat

END ' End of program

Also tried them all and none of the LED turned on.

LED1 VAR PORTA.2 ' Pin LED Test
LED2 VAR PORTA.3 ' Pin LED Test
LED3 VAR PORTA.4 ' Pin LED Test
LED4 VAR PORTA.5 ' Pin LED Test
LED6 VAR PORTB.0 ' Pin LED Test
LED7 VAR PORTB.1 ' Pin LED Test
LED8 VAR PORTB.2 ' Pin LED Test
LED9 VAR PORTB.3 ' Pin LED Test
LED10 VAR PORTB.4 ' Pin LED Test
LED11 VAR PORTB.5 ' Pin LED Test
LED12 VAR PORTB.6 ' Pin LED Test
LED13 VAR PORTB.7 ' Pin LED Test
LED15 VAR PORTA.6 ' Pin LED Test
LED16 VAR PORTA.7 ' Pin LED Test
LED17 VAR PORTA.0 ' Pin LED Test
LED18 VAR PORTA.1 ' Pin LED Test

TRISA = 0 ' PORT A is output
TRISB = 0 ' PORT B is output


RPT:
PAUSE 1000 ' WAIT 1 SECOND
LED1 = 1 ' Turn Pin LED ON
LED2 = 1 ' Turn Pin LED ON
LED3 = 1 ' Turn Pin LED ON
LED4 = 1 ' Turn Pin LED ON
LED6 = 1 ' Turn Pin LED ON
LED7 = 1 ' Turn Pin LED ON
LED8 = 1 ' Turn Pin LED ON
LED9 = 1 ' Turn Pin LED ON
LED10 = 1 ' Turn Pin LED ON
LED11 = 1 ' Turn Pin LED ON
LED13 = 1 ' Turn Pin LED ON
LED15 = 1 ' Turn Pin LED ON
LED16 = 1 ' Turn Pin LED ON
LED17 = 1 ' Turn Pin LED ON
LED18 = 1 ' Turn Pin LED ON
PAUSE 1000 ' WAIT 1 SECOND

LED1 = 0 ' Turn Pin LED OFF
LED2 = 0 ' Turn Pin LED OFF
LED3 = 0 ' Turn Pin LED OFF
LED4 = 0 ' Turn Pin LED OFF
LED6 = 0 ' Turn Pin LED OFF
LED7 = 0 ' Turn Pin LED OFF
LED8 = 0 ' Turn Pin LED OFF
LED9 = 0 ' Turn Pin LED OFF
LED10 = 0 ' Turn Pin LED OFF
LED11 = 0 ' Turn Pin LED OFF
LED13 = 0 ' Turn Pin LED OFF
LED15 = 0 ' Turn Pin LED OFF
LED16 = 0 ' Turn Pin LED OFF
LED17 = 0 ' Turn Pin LED OFF
LED18 = 0 ' Turn Pin LED OFF

GOTO RPT ' Repeat

END ' End of program

[JohnPaul]

JoeS,

Your posts noted and changes made. I am pondering why my chip is not working. If the chip is damaged, won't the programmer verify step resulted in an error? What's next after LED test failed? I have another pci16gf627A chip. I am afraid that I might damage it too.

Regards,
JohnPaul

[JohnPaul]

ski,

I like your 'heartbeat' practice. I would adapt it as my practice too.

Regards,
JohnPaul

[skimask]

ski,

I like your 'heartbeat' practice. I would adapt it as my practice too.

Regards,
JohnPaul

Put a voltmeter on the OSCx pins. You should get around 2.5v with an external oscillator, or if you've got OSC2 setup as an Fosc/4 output.
I wouldn't think you smoked a chip...as has been noted before, PICs are fairly tough chips, not unbreakable, but tough.
And if for some reason, your PIC is running on the 48khz internal clock, your program will run about 83 times slower than it should...in other words it'll take 166 seconds for your LEDs to blink.

[JohnPaul]

Ski,

Hmm. I am not yet familiar with the OSC parameter settings.
I did the LED test without any of the additional DEFINE and @ statements beside the ones that I posted.
I waited 5-10 minutes for the LED to light up on pin 6. But the chip and bottom of the bread board were getting hot so I pulled the power off.


I just checked again. I think that I might have really burned my chip this time.
I placed the voltmeter on 0 and +5V, and I would read +5v. But the moment I connect my +5v cable to VDD (pin 14). The voltmeter reading would drop to 1.67v?


Regards,
JohnPaul

[skimask]

Ok, get rid of everything but the power supply (connect a light bulb across it, verify 5v under a small load, use 3 alkalines or 4 NiCads instead of a power supply), the PIC16F627A, an LED with a 300-ish ohm resistor in series, 10K pullup to +5v on MCLR, and some sort of crystal/oscillator setup on OSC1... and put a small cap across Vdd and Vss on the PIC (very important step here!)

Double check your pin 1 on the PIC and plug it in.
Break it down...break it WAY down to bare bones.

Rewrite the program, simplify it as far as you can, one LED or a group of LEDs, doesn't matter, same thing, blink the LED...

Let us know what you've got after you get it broke down...

I don't think you've fried anything (although it's entirely possible), I think you're just forgetting something basic, and when that gets figured out, everything else will fall into place faster than you can spend money on it

[JohnPaul]

Dear Ski,

Hahaha... Blinking the LED is the first project in the book and I thought it's so simple so I read all the projects but did not tried any of the LEDs .... skipped all the project all the way to the LCDs. Now, I am back... to LED1.BAS

I will get a new chip and tried the LED Blinking tomorrow and start anew.
It's late now.

Thank you very much! I greatly appreciate your help.

Regards,
JohnPaul

[Archangel]

JoeS,

Your posts noted and changes made. I am pondering why my chip is not working. If the chip is damaged, won't the programmer verify step resulted in an error? What's next after LED test failed? I have another pci16gf627A chip. I am afraid that I might damage it too.

Regards,
JohnPaul

Hi JohnPaul,
You would think so wouldn't you, but the short answer is no, I have killed a few PICs and had programs verify fine, I think I killed the output transistors while the core of the pic remained undamaged. You would do well if using an old breadboard to either replace it or use an ohmmeter to verify all connections, I have been led to the land of little hair as a result of these.
JS

[JohnPaul]

Joes & Ski,
Thank you for the help.

JoeS,
Using an Ohmeter, which pins do I tap, what to expect and why? I would also do the Ohmeter test on a new chip alongside with this chip in question.

Regards,
JohnPaul

[skimask]

MCLR / Vdd - 5v (if running a 5v power supply, otherwise, take all these reading and divide them down accordingly)

Vss - 0v

OSC1 / OSC2 - with an external oscillator/crystal, somewhere around 2.5v give or take, because the meter is really reading DC, it's catching the average of the DC, which since it's going high/low/high/etc, is around 2.5v.

Pins set to an input will most likely read about 2.5v, or a suitable fraction of the main power supply voltage.

Pins set to output and logic low will be between 0v and about .6v

Pins set to output and logic high will be around 7/10 of the main power voltage.

All interconnects on your breadboard should be practically a dead short, like less than about 10 ohms or so. Don't forget to check your multimeter leads themselves for resistance.

Hopefully this is what you were asking about. Sounds a tad bit basic to me, but that's just me...

By checking the new chip against the old chip alongside it in identical circuits, you are doing what I call a 'signature check', good troubleshooting technique, but it really only works if you've got a couple of known good working setups to verify another bad setup.

[Archangel]

Joes & Ski,
Thank you for the help.

JoeS,
Using an Ohmeter, which pins do I tap, what to expect and why? I would also do the Ohmeter test on a new chip alongside with this chip in question.

Regards,
JohnPaul

Hi JP,
Pretty much as skimask said, just check from the leads of the components to where they are supposed to be connected ( the other component ). These breadboards get really spooky over time. Darrel told me he only uses them once. That's too rich for my blood but my time is perhaps less valuable. Certainly I do not do this for a living. I dissasembled my old breadboards and was very surprised at what I found in the way of wear and corrosion. This is especially important on the VSS & VDD connections so power flows through the device in the way it's designers intended, otherwise very strange current paths can exist and FRY something.
JS

[JohnPaul]

Hey, folks. No progress today... Hehehe... I actually mean I slacked off. I could not find my other 627A. Use of magnifier did not helped. I would try the 84A but have to use OSC chip or I have to use my 40 pins. I could not wait for the weekend to come.

What is the most advanced PIC chip one could wish for? I like my 627A since it has internal OSC.

I am reserving my 40 pins for more complexed project in the future.


Cheers!

John Paul

[JohnPaul]

JohnS,
I bought this regulated variable PS. They go by 1.5, 3, 4.5, 6, 9v, 12v.
No +5v! I like it because it's so portable than those high Amp PS. So I was playing with the PIC with 4.5v and ocassionally switching to 6v. Could I have caused the untimely dead of my PIC?
Later, I retrieve one of my breadboard with a T7805. Just to make sure the LCD and Chip now has the recommended (or was it REQUIRED) voltage?
Hahaha...

Regards,
JohnPaul

[skimask]

JohnS, I bought this regulated variable PS. They go by 1.5, 3, 4.5, 6, 9v, 12v. No +5v! I like it because it's so portable than those high Amp PS. So I was playing with the PIC with 4.5v and ocassionally switching to 6v. Could I have caused the untimely dead of my PIC? Later, I retrieve one of my breadboard with a T7805. Just to make sure the LCD and Chip now has the recommended (or was it REQUIRED) voltage?
Hahaha...
Regards,
JohnPaul

The PIC (and everything else mentioned so far) will run just fine off 4.5v, and the occassional switchover to 6v probably won't hurt it much either. Datasheets say 7V is 'absolute maximum' rating, not recommended for any length of time. I've accidentally ran a couple of my PIC's at 9v before, they still run, not saying they're not damaged and won't fail before the others, but they do still work.