Lost ability to connect via USB

[Mjolinor]

Th 8U2 processor is very voltage intolerant unlike the 2560. My Wanhao has stuffed the USB serial so I just bought another stand alone USB<>serial and picked up the TX and RX lines from the board itself.

[csader]

Th 8U2 processor is very voltage intolerant unlike the 2560. My Wanhao has stuffed the USB serial so I just bought another stand alone USB<>serial and picked up the TX and RX lines from the board itself.

Interesting idea...I'm not super familiar with the pinout on a Taurino 2560...which pins are TX/RX for serial? I think i have an extra USB to Serial cable lying around somewhere.

[Mjolinor]

You would have to look at it or find a schematic on the net. It is usually pretty obvious which lines they are because they go from one processor to the other usually with a surface mount resistor inline, you just need to turn that resistor round on the pads so it is still connected to the 2560 and solder a small wire on the other end of the resistor, 2 wires +1 wire for ground between the two boards.

I used one of these:
http://www.geeetech.com/iduino-due-p...ter-p-655.html

The small board on that page. I would not advise you to buy from Geeetech, they truly suck at support and build quality and are somewhat less than honest in their descriptions.

[printbus]

The schematic for any of these Arduino clones is still the same as the Arduino branded MEGA2560. They have to follow the same pinout in order for firmware to be portable from one clone to another. The component and pad locations might vary some, but the basics of the schematic is pretty standard.

[csader]

Colin's assessment is a fried USB port. Ordered a replacement arduino.

[Mjolinor]

You should try programming the 8u2 before replacing the board. Very easy to make a programmer.

[adamfilip]

ive run into issues with not be able to connect, sometimes i need to go into device manager and select the port (port 5 in my case)
right click and hit disable and then do it again and enable
then unplug and replug the usb cable from the printer and then after that it usually works for me.

[csader]

You should try programming the 8u2 before replacing the board. Very easy to make a programmer.

That device you linked to is double the cost Colin's charging for a replacement board. Don't see the benefit.

[Mjolinor]

There is no benefit in that case.

A replacement processor board for my Wanhao is around £90 so adding another serial is well worth it and a lot quicker than replacing the 8u2.

[printbus]

...Ordered a replacement arduino.

At the near-commodity pricing Arduino boards go for, that's likely what I'd have done.

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This is mainly for future readers that run into the thread in searching USB issues, but here's some basic background info related to programming the MEGA2560 board.

As already discussed, there are two Atmel AVR processors on the board. Our printer firmware is uploaded and stored in the flash memory inside the ATMEGA2560 processor. General AVR processors aren't very efficient at dealing with USB, so the Arduino reference design for the MEGA2560 board adds a specialized ATMEGA18U2 processor for handling the USB interface. A serial link connects the two processors.

The ATMEGA18U2 flash memory is preprogrammed with the firmware needed for the USB interface processing. Arduino processors like the ATMEGA2560 are typically preprogrammed with at least a download bootstrap that allows the flash to be updated via the USB interface and the ATMEGA18U2 processor.

For programming, removable DIP style parts can be installed into a programmer board such as the Atmel STK500. The AVR processors I'm familiar can also be programmed in-circuit, as long as access to certain processor pins is made available for connection to the external programming hardware. Surface mounted parts like those on the MEGA2560 are typically programmed this way. The in-circuit programming could be used to attempt restoration of functionality to either processor on the MEGA2560 board.

Atmel refers to the in-circuit programming as In System Programming, or ISP. Atmel defines two standard connection schemes for this - a 3x2 header or a 5x2 header. Programming hardware typically supports either; Arduino opted for the 6-pin 3x2 header. Referring to the Arduino MEGA2560 reference design, connector ICSP is the programming header for the ATMEGA2560, and connector ICSP1 is the programming header for the ATMEGA18U2.

While plans for the external programmers can be found on the web, they're also not expensive to buy. I haven't used it, but as an example, SparkFun has the Pocket Programmer for $15 USD. For my general AVR development, I have the Atmel AVRISP mkII dongle programmer. In nearly all of my personal non-Arduino and non-USB designs, I run the ISP connections to a panel connector so that I can reprogram the AVR processor without opening anything up.

Most, if not all, of the external programmers leverage a protocol that started with the STK500 board-level programmer. The most common software tool used to support the protocol is avrdude. Those that have ran into issues programming their MEGA2560 may see errors related to STK500 or avrdude; now you understand why. Arduino uses avrdude as the programming utility.

Source or at least upload files for the ATMEGA18U2 and the boot loader on the ATMEGA2560 are likely available from Arduino or elsewhere.

While the programming isn't hard, there can be lot to grasp the first time through it, especially when the avrdude tool command line interface has to be used. I wouldn't like to try and figure out a new programmer and the programming utility when I also have suspect hardware to work with.

Those looking for more information on using AVR processors outside the Arduino realm are encouraged to look into the WinAVR environment that Arduino started with. Forum www.avrfreaks.net is arguably the largest gateway to user knowledge out there.