Max/232 Bootloader problems - Schematic attached...

[rossfree]

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

[skimask]

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

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

[rossfree]

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

[skimask]

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

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...

[rossfree]

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

[Archangel]

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

Skimask, did you see that ?
JS

[skimask]

Skimask, did you see that ?
JS

Yep...'bout crapped myself too