Power/booting problems

I havent needed help in a while, while i have been plugging away at my project. but there are now a few bugs i cant find. i am supplying my Arduino Mega 1280 from a Li Ion battery threw a boost circut supplying 5v. it will run fine if i have the computer connected to it than disconnect the computer, but when i just turn it on from the external power it will not run the code.

What could be causing this? i have alot of serial prints.

that is just to start. thank you in advance.

Will it stare when you power it up with the battery and then hit the reset button?

well i have a shield ontop of the arduino, and the reset button is in the middle so that was difficult, so i just jumped 5v to reset, and it didnt start.

You need to put the reset to ground to activate it.

Thank you, well i tried that, and i can see that it started the sketch but it didnt finish even the startup.

i have a GLCD, shield. and it has "noise" all over it.

i have alot of serial debug prints, sending to the usb port, will that affect anything if there is no place for thoes to go?

If the serial has no place to go it dosn't matter. It sounds like you have a grounding issue coupled with a power issue. Try powering it off your batteries but connecting a ground back to the computer and see if that lets it run. If so then we know what to address.

how would i go about grounding it to the computer without powering it by the computer.

BUT i did find when i was trying to find out i have my battery boost conencted to the 5v rail insted of the vin rail. i am going to switch thoes when i get home. i am also in prossess of sending all my debug prints to serial3 witch is my thermal printer.

What is the voltage output of your boost circuit, it should be +5V for maximum efficiency.

Just connect a wire to a signal ground on the computer, or hack up a lead.

yes the boost circuit is outputting a regulated 5v supply. and connecting to the signal ground made no change.

although my serial debug prints to the serial3 have narrowed it down to my sd card is not beginning. All the Serial ports begin, the RTC Begins with the correct time, than i do not recieve the begin sd statement.

What could cause the SD card not to begin, when on external power yet while off the computer it runs fine?

THANK YOU so much for all your help.

thank you again, i set the SPI speed down to a eighth and it is working. no on to the rest of the to do list...

im just going to type it here so i dont forget what i have to do, if anyone is interested in what this does let me know, i plan to do somethign for when it is completed.

fix single digit minutes and seconds for display (from RTC) make file list "clickable" and have it not update every touch. add wifi with page hosting for remote view of graph and data retrieval add ability to set RTC from the device itself. find way to add PS/2 Keyboard without using the hardware interrupt (they are already being used) add del button to graphing view/chart view add chart view check wireing. and fix switches.

I'm going to take a shot in the dark and chock it up to noise. You said it's a boost converter... so... switching? Have any filter caps?

It is not just a matter of capacitors with noise from a switcher, it is more to do with layout and screening.

Whaaat? Caps don't solve everything? Aw man. :D

Not this time :P