Max/232 Bootloader problems - Schematic attached...

[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

[skimask]

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

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

[Pic_User]

Hi Ross,

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

Bingo!
-Adam-

[rossfree]

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.

[Pic_User]

Hi Ross,

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

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-

[rossfree]

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!!!

[skimask]

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?