Odd download problems

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parts-man73

Member
I just recently started having problems downloading to my 18X chips. I can check the firmware via the "options..." menu. I can also "clear hardware memory" without errors. But when I try to download a program, it errors out with a "memory verification error at byte ???"

The possible causes it lists are
1.Cable removed during programming
2.Power removed during programming
3.incorrect power supply (e.g. 6V) used

I obviously am not removing the power or cable during programming. The power supply I am using is a wall wort that is providing 5 volts. I've checked with my digital multimeter and I find 5.2 volts on pin 14

If I press the reset button (pulling pin 4 low) and release the button at the same time I start my download, it will take the program. But if the program is too large, it will error again, but at a higher byte. (the error code displays the byte at which the memory verification error occurred) So I can never load really large programs.

The only thing I can think of that is different, is that I am using a different computer now, maybe the serial port isn't compatible. It is a desktop computer, I know some have had problems with laptops.
I haven't tried this yet, but should I try using a MAX232 in my download circuit? I don't have any suitable transisters in my supplies to handle the inversion nessesary for this chip, but if need be, I can get some monday when my local electronics store opens.

Thanks,
Brian
 
M

Michael 2727

Senior Member
Is the wall wart a 5V DC regulated one ?
If not how big is the capacitor inside it -
you won't know obviously.
If you place the 5V supply across a 4 inch
Loudspeaker with a 330 Ohm resistor in series and you hear any HUM the internal
supply filter capacitor is probably minimal.
Try adding a 1,000 µF Electrolytic across the supply for extra stability.

PS:
If the wall wart was a really crappy one to
begin with and had no capacitor at all it
would be AC modulated DC as the output.
By adding any capacitor the output voltage
will nearly double be aware of this.


Edited by - Michael 2727 on 07/05/2006 01:24:48
 
Y

ylp88

Senior Member
Definietly try using batteries (3 x 1.5V AA) so that you can isolate any power instability problems. Don't try using a MAX232 - it inverts the download signal and this will make sure that the download DOES NOT work! It will also make the circuit more complex leading to higher potential for more problems.

<b><i>ylp88 </b> </i>
 
P

parts-man73

Member
I may have found a solution here... I read the other thread with a similar problem. I tried the battery power solution and it did help. still an occaisional error though.
I went back to my 5.3 volt wall wart and put a 1n4004 diode on the supply to my solderless breadboard, and it shaves about half a volt off the supply voltage. Now I have error free downloads.

I think I will soon try a power supply like this one http://www.sparkfun.com/commerce/product_info.php?products_id=114

Brian
 
premelec

premelec

Senior Member
When I have had problems it usually has been that there is an instruciton in a running program like 'sleep' which interferes with a download ... if you disconnect power, start download and _then_ turn on power this usually solves _that_ problem [remember capacitors in PS must discharge for power to actually be off].
 
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