Max/232 Bootloader problems - Schematic attached...

Hi all,

I've struggled alone on this for long enough. I've bread-boarded the MAX232 circuit with the 16f876 and it works... but once on my circuit board it does not. This is a new board, all chips socketed except the thermocouple amplifier.

The only socketed components currently on the board are the MAX232 and the 16f876. Nothing else.

The 876 has been loaded (on the breadboard) with a "blink" program and it works.

I am using Picbasic Pro and Microcode Studio. I am also swapping the MAX and 876 between the new circuit board and a breadboard. So those two components are not bad.

Could there be some suttle difference in my circuit board that I'm not finding?

Please let me know if you see something I do not. I designed this circuit board but I am an AMATEUR. I did my best. The board also uses a 16f88 (also socketed). I left off a pull-up resistor on MCLR for that chip... it will be rectified later.

I'm getting a "reset controller" message when I try to bootload to the 876 on my new circuit board. Using the same computer, program, processor and Max232 on my breadboard... it all works. Go figure!

Hope you have some suggestions.

Many thanks!

Ross

Quote:

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Originally Posted by rossfree

Hi all,
I've struggled alone on this for long enough. I've bread-boarded the MAX232 circuit with the 16f876 and it works... but once on my circuit board it does not. This is a new board, all chips socketed except the thermocouple amplifier.
The only socketed components currently on the board are the MAX232 and the 16f876. Nothing else.
The 876 has been loaded (on the breadboard) with a "blink" program and it works.
I am using Picbasic Pro and Microcode Studio. I am also swapping the MAX and 876 between the new circuit board and a breadboard. So those two components are not bad.
Could there be some suttle difference in my circuit board that I'm not finding?
Please let me know if you see something I do not. I designed this circuit board but I am an AMATEUR. I did my best. The board also uses a 16f88 (also socketed). I left off a pull-up resistor on MCLR for that chip... it will be rectified later.
I'm getting a "reset controller" message when I try to bootload to the 876 on my new circuit board. Using the same computer, program, processor and Max232 on my breadboard... it all works. Go figure!
Hope you have some suggestions.
Many thanks!
Ross

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Are you using one of those solderless breadboards?
We had a discussion here awhile back about how crappy those things can be sometimes.
A few people, myself included, basically came to the conclusion that it's not a bad idea just to throw them away after awhile and replace them. The contacts inside them go to crap, cause intermittent problems, etc.etc. Just not worth the headache :)

Hi Ross,

Quote:

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Originally Posted by rossfree

I left off a pull-up resistor on MCLR for that chip... it will be rectified later.

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Bingo!:)
-Adam-

Thank you for replying...

I am not having trouble with the breadboard. It's my new circuit board that does not allow me to program the chip. On the breadboard, I can program just fine.

I do have a pull-up resistor on the circuit board for the 876. I will have to add one for the 16f88 when I start working with that part of the circuit board.

The circuit board has a jumper that allows me to chose which PIC I am programming. Both will have the "bootloader" programs in them.

Hi Ross,

Quote:

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Originally Posted by rossfree

It's my new circuit board that does not allow me to program the chip.

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You may have to post pictures of your PCB.

Did you etch it yourself?
Double sided?
Does it have plated through holes?
Are there any solder bridges?
Did you accidentally lay it out as a “mirror image”?
Are all the PCB parts installed with correct polarity?
Are external wires attached to the correct places?
Is the MCLR resistor really 4.7k not 4.7 Ohms (4k7 not 4R7)?

A picture is worth a thousand questions!:)

-Adam-

To Pic_User,

Thank you for your reply.

Did you etch it yourself? No... PCB123. I made two boards. No solder-mask or SS. And I found a problem earlier... my metal can crystal was intermittantly touching traces under it. Ha! Fixed.

Double sided? Yes.

Does it have plated through holes? Yes.

Are there any solder bridges? I've been over it carefully. Can't find any. Doesn't mean I didn't miss something. But it's not a huge board. I've checked voltages and ohm'd pins. Nothing stands out as blatantly wrong. Power supply is cool, no hot parts at all. 5 volts where expected. 12 volts where expected... etc.

Did you accidentally lay it out as a “mirror image”? Nope.

Are all the PCB parts installed with correct polarity? Silk screen was wrong on LEDs... put them all in backwards. Bother! :-) I corrected it earlier.

Are external wires attached to the correct places? No external connections as yet. Only power supply, Max232, 876, and T/C amp on board. Trying to get this going before pushing on. One thing at a time. :-)

Is the MCLR resistor really 4.7k not 4.7 Ohms (4k7 not 4R7)? Good question... I checked it earlier. It is correct. And the 100 ohm resistor on pin 9 is correct also.

If I had pics of the board I would post. I'm including a PDF of the artwork and traces. Blue traces on bottom of board... Red on top.

I have three operator push buttons and a POT on back side of board and an in-line connector strip for the LCD (also on back of board). The LCD is not connected. And I have not put the operator POT on the board yet either (R23).

I know it is unlikely that you can do much... but just maybe someone will catch something I missed.

HELP HELP HELP! :-)

Thank you!!!

Do you have 16F876 or 16F876A selected in your programmer, or which chip do you have?
It's a thought...
How about the PGM pin on the '876? Do you have the right pullup/pulldown on that? Are you using high voltage on the breadboard and low voltage on the PCB?

Do you have 16F876 or 16F876A selected in your programmer, or which chip do you have?

I'm using a 16f876. Microcode Studio is also set to 16f876.



It's a thought...
How about the PGM pin on the '876? Do you have the right pullup/pulldown on that? Are you using high voltage on the breadboard and low voltage on the PCB?

I am holding MCLR high with a 4.7k resistor. I don't think I need to do any more than that. I am using a MAX232 connected to TX and RX and pin 9 of the MAX is connected thru a 100ohm resistor to MCLR on the chip.

It asks for a reset when I try to program... but pressing the reset button on my circuit board does nothing for programming the chip... it does pull pin1 of the 876 (MCLR) from 5vdc to gnd.

I'm still checking voltages... and the thing that sticks out is that the voltages on the MAX232 on my circuit board are different from those on my breadboard. And all of this works on my breadboard... using the same MAX232 and the same 876. :-[

One voltage that really stands out is on pin 8 of the MAX232. On my breadboard... with the serial cable plugged in (from my computer) and the breadboard powered up, I read -10vdc. On my circuit board... under same conditions, it reads 0vdc. There is something wrong there. I will look at it closer.

If you haven't had a chance to look... I've posted a schematic and board layout in this thread.

Thank you for helping out!

Still looking for an answer.

Ross

Quote:

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Originally Posted by rossfree

I am holding MCLR high with a 4.7k resistor. I don't think I need to do any more than that. I am using a MAX232 connected to TX and RX and pin 9 of the MAX is connected thru a 100ohm resistor to MCLR on the chip.
Ross

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Not MCLR-------PGM different pin, different function. It'll cause programming problems depending on method used to program.

I just checked the data sheet on the 876 (is everyone proud of me! :-)

Using the bootloader and a MAX232, I am using high voltage programming? Yes? and the PGM pin is associated with Low Voltage Programming and In-Circuit Debugging. So I think I am ok there.

I DID however find a major problem.

Yep... I did it... I think I read the drawing of my 9-pin D-sub in reverse... all of my pins on the board are mirrored. :-P

SOOoooooooo... I think I found my problem. Wierd that it should give me almost all of the same voltages on the MAX232 pins except one. ???

I'll yank the D-Sub and flip it to the other side of the board and see if that cures my ills.

Will get back shortly.

The amateur in me is showing. :-)

Thank again!

Ross

Quote:

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Originally Posted by rossfree

I DID however find a major problem. Yep... I did it... I think I read the drawing of my 9-pin D-sub in reverse... all of my pins on the board are mirrored. :-P I'll yank the D-Sub and flip it to the other side of the board and see if that cures my ills. Will get back shortly. The amateur in me is showing. :-) Thank again!
Ross

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You ain't the first one to pull off the ol' "flipped the D-sub around to the other side of the board the wrong way around in reverse" trick, or even do the same thing to a double row IDE connector. Good luck...

Happiness is a board that programs with the bootloader!

That was the problem... the 876 is happy and computer is chitting at it merilly. It was the mirrored D-Sub. A mistake I can live with... but assure you will be corrected for future projects.

Thank you Skimask for your comments. And thanks to those that helped out.

Love the forum!

Ross

Quote:

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Originally Posted by rossfree

"Thank you Skimask for your comments." And thanks to those that helped out.

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Skimask, did you see that ?
JS

Quote:

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Originally Posted by Joe S.

Skimask, did you see that ?
JS

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Yep...'bout crapped myself too :D

Alright... let me re-phrase that.

Thank you Skimask for your help and polite comments! And again let me say how much I appreciate all who contributed to the correction of my most dispickable mistakes.

GEEEEZZZZZZZZZEEEEE!

:-)

Quote:

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Originally Posted by rossfree

Alright... let me re-phrase that.
Thank you Skimask for your help and polite comments! And again let me say how much I appreciate all who contributed to the correction of my most dispickable mistakes.
GEEEEZZZZZZZZZEEEEE!
:-)

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It's all good...no sweat...

Quote:

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Originally Posted by rossfree

Alright... let me re-phrase that.

Thank you Skimask for your help and polite comments! And again let me say how much I appreciate all who contributed to the correction of my most dispickable mistakes.

GEEEEZZZZZZZZZEEEEE!

:-)

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Hi rossfree :)
I wasn't woofin' on you ! Old skimask has taken some heat lately from a few nonreaders of the holy green book, and I was pointin' out that someone appreciated him. Oh and there are no dispickable mistakes, a few dipstickable ones perhaps, but those only prove humanity :)

Quote:

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Originally Posted by Joe S.

Old skimask has taken some heat lately from a few nonreaders of the holy green book, and I was pointin' out that someone appreciated him.

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That's the facts...
I'll take a flipped part on a PCB anyday over a non-believer/non-reader/non-digestor of the information in the holy green book...not to mention the teachings of the great PBprophets 'DT', 'Mr_E', and 'Melanie' and the writings contained herein...
All MUST bow to their wisdom and their teachings...for they are the truth and the truth shall set your hardware free to do your bidding.
Lessor PBprophets, if I may consider myself that, well, maybe you'll take what I say with a grain of salt and a skeptical eye...over a beer...next to the bonfire...with a shot of tequila

Skimask, there for a minute I was looking for a lamb to slaughter. Your words made me ssshhhhiiiivvvverrrr... no wait... I had my had on the fuse block. Made me think I should be naked with lit candles all around, sitting on a rough stone floor with my legs crossed...

but then I came to my senses... and went back to watching Opra.

I do this stuff as a hobby... It allows me to play at work once in a while. Mostly I'm a mechanical guy. I've designed lots of machines with electronics guru's doing my bidding. **evil laugh**

I especially liked hearing my electronics co-worker, guru, companion, best friend... comment that when we finished designing and building a machine, everyone would coo and ahh about how cool the machine (that I designed!) looked and worked. He said nobody appreciated his work... the electronics inside the machine that made all of those things play.

I said to him, "That's because electronics are SUPPOSED to work."

HA HA HA HA HA HA HA HA HA!!!

He was a good sport! And he taught me pretty much everything I know about electronics. I'm nowhere near his level. I don't pretend to be. The little I know allows me to piddle with processors and programming. That's enough. I'm happy.

I don't wear a watch cause everyone else wears one. I don't own a cell phone cause in an emergency there's always one around...

And there's this forum. Need I say more?

Life is good.

Ross

Well, there ya go...
Now go break something....and fry something else, let all the magic smoke out of it!!!! :D