replace mega16U2 on Mega2560

So a while ago the mega16U2 some how burnt out on me, so I built a parallel programmer so that I could program my Mega2560 anyways, unfortunately, I desire to have serial communication with a computer now, but since I don't have the handy dandy 16U2 to do the serial to USB conversion, I'm at a disadvantage, so my question is, how can I remove and solder on a new ATmega16U2 in place of the old one?

PS: the reason I believe the current 16U2 to be fried is cause my mega doesn't show up on my computer at all, and when attempting to reflash the 16U2 with my parallel programmer, it fails miserably with several errors, including not returning a device signature corresponding to the 16U2

Any help will be greatly appreciated, thanks in advance :smiley:

hot air or chipquick would remove it

or if you have a FTDI or similar cable you could just cut the traces and use that though the header connections (or make a level shifter/inverter and use a real RS232 port on the computer)

how do I get the new chip on?

wick the pads dry, tack a couple corners and a steady hand

or solder paste and hot air

maybe a couple other options, though due to the size of that IC its going to be finicky (and don't forget you have to program it)

Do you have another arduino? I am assuming that you are using a Parallel Programmer, that you do not have any other type of "pocket programmer".

like I said, I've got a parallel programmer, so I can program the chip through the ICSP header next to it, and no, I don't have any other of these "pocket programmers" that you speak of, nor do I have another arduino. I'm thinking I need to find a different solution though cause Atmel refuses to send samples to anyone using anything other than a business email, maybe I can get a chip from Microchip or something, anyone have some recommendations on chips that are good for serial to USB?

for free? not really

whats the difference between the ATMega16U2-MU and the 16U2-MUR?

they seam to be the same package type and all that good stuff, but what does the R mean?

c0d3Man:
like I said, I've got a parallel programmer, so I can program the chip through the ICSP header next to it, and no, I don't have any other of these "pocket programmers" that you speak of, nor do I have another arduino. I'm thinking I need to find a different solution though cause Atmel refuses to send samples to anyone using anything other than a business email, maybe I can get a chip from Microchip or something, anyone have some recommendations on chips that are good for serial to USB?

Well check out the FTDI FT232RL chip as used in the older versions of the arduino board before they switched to using Atmel chips as USB serial converter chips. The driver for the FTDI USB converter still is part of the current IDE installation distrubution so that the IDE can continue to support older arduino boards.

Lefty

-MU vs -MUR is just how the parts are packaged for shipping.
I'd also opt for connecting an FTDI Basic or CP2102 module to the +5, Gnd, DTR, Rx, and TX pins for serial downloading.

Assuming you will be unable to replace -16U2.

I'm hoping to get a 16u2 soon, I was thinking of trying a heat gun to desolder the bad chip and then solder on the new chip by applying some solder to the pins on the board and using the heat gun on the chip because of it being a VQFN, but I'm worried about causing problems for nearby components, like the RX and TX LEDs, and the other various components that are very close, If I can't get that done then I will definitely check out the FTDI chip(s).

Any tips on soldering with a heat gun? or a more efficient way of soldering on the QFN chip? I though about possibly building a reflow oven thing and using that[as a last resort for replacing this chip], but I don't want to melt the plastic on the pin headers.

"Any tips on soldering with a heat gun?"
You really need a nozzle to control airflow.
Such as
http://www.mpja.com/prodinfo.asp?number=15284+TL
or similarly sized for the part you are trying to rework.

what does that tip actually do? cause I had been thinking of just using a heat gun my mom has, which I think has a nozzle that is roughly as small as the chip [actually I think its a little smaller than the chip, and its a round hole], I had not realized I would need a certain tip.

The nozzle keeps the 300 degree celsius airflow to the small area around the chip so all sides are heated evenly.
A round nozzle like this
http://www.mpja.com/prodinfo.asp?number=15283+TL
may be used also have to move it all around the chip to get all sides melted at the same time.

So Atmel is being gracious enough to send me a "sample" of the 16U2, but the nozzle on my mom's heat gun is about the size of a dime, so I guess I'll have to find some way of shrinking the nozzles size

just use an iron, its not that hard, without decent hot air accesories you stand more of a chance of blowing everything around the chip off the board

theres nothing for me to use the iron on though, thats the problem, the package they use for the 16u2 on the Mega2560 is pinless, it just has exposed spots under the chip, and on top of that, its a VERY tiny chip

Well I removed the old chip and put on the new one, but somethings wrong, the chip showed up on my computer, when I first plugged in my Arduino to program the new chip, as a atmega16u2 DFU mode, so I powered up FLIP and burned the firmware through the USB port (one of the things wrong is that I can't program the chip through the ICSP header, it doesn't respond with anything, it appears that it sees the chip as being there, partially (hard to explain at the moment cause its hard to remember and its been several days since I had tried to program it, college was keeping me busy), anyways I do have issues trying to burn the bootloader back onto the mega2560, I think its issues from how I modified my Parallel programmer, I had resoldered all the wires so as to shorten the 2 foot 8 inch cable to a 2 foot 7 inch cable and soldered the exposed wire in the cord (which comes in contact with the "Faraday" shield) to try and help block interference, though the length of the cord is probably too long, but I digress, when I try to burn the bootloader back onto the mega2560, most of the attempts end with a supposedly successful writing, but 2 of the fuses are changed in the process, and I am still unable to communicate serially with my Arduino or even program it.

any insight on the length of my parallel cables?
what about theories of what may be wrong on my Arduino that is still preventing serial communication? it doesn't appear to have any shorts (visible at least), and the only two contacts that I lifted from the board by accident when applying new solder for the 16u2 where for unconnected pins on the chip and are therefore unneeded.

also as a side note, it seams that my Arduino is now partially powered when I plug my parallel programmer into the iscp headers (it happens with both); I don't recall it doing this before the work and therefore leads me to believe that there is a short somewhere.

again thanks in advance for any help, comments, insight, or anything