AT90USBKEY / Arduino compatability

Hey guys, I am a musician and am trying to interface my windows PC with an old mid 80's sampler unit. Currently there is a kit for interfacing the sampler with windows ( firmware and driver already made, as well as the interfacing software)

Since there is a rs422 port on the 80's sampler basically what is needed is a fancy rs422 to usb adapter. The current kit is using the AT90USBKEY by Atmel, but the availability and bulk of the board isn't very appealing.

I have the current diy plans for the at90usbkey board, but was wondering if someone could help me convert it over to arduino? Would be willing to pay some money for plans.... I really want to be able to interface my vintage sampler !

Thanks again for helping a musician use archaic hardware in the studio! :smiley: :smiley:

What's the protocol? My experience with RS422 is that it's just a differential signal version of RS232. you can even wire an RS422 to RS232 by connecting the T- and R- lines to GND.

To connect to an Arduino, just get the rs422 equivalent of a MAX232.


well RS422 adapters currently on the market do not support synchronous communication, which this old sampler is in need of.... all far over a musicians' head :wink:

well there is a max422 IC, hmmm could that be the equivalent?

No, I think the MAX422 is an (obsolete) op-amp of some kind.

Your device is not a standard serial interface - it is synchronous. Standard RS232/RS422 is asynchronous.

Looks like you've got a non-standard device with a custom interface and custom drivers to talk to that interface. IMO this will be non-trivial to implement.


any more specifics about the project?

Here's a cheap AT90USB1286 board at $24:

This is the essentially the same chip as on the AT90USBKEY board, with the distinction that the AT90USB1287 used in that board also supports USB OTG (on-the-go, a type of host-mode) whereas the AT90USB1286 used in the teensy++ doesn't. Reading the description of your project I guess it shouldn't make a difference. I'm pretty sure you can take the code already written for the AT90USBKEY and just run it on a teensy++. You can probably even get away with using a 'normal' teensy (slightly cheaper, less capable chip), although that might need a little extra work.

Form factor shouldn't be a problem either, methinks. I've seen people use teensies and cover them with heatshrink to get a nice USB adapter without any nasty cables sticking out.

By the way, I've looked at the schematics of the project you mentioned, pretty cool stuff. I'd definitely go for a teensy, perhaps breadboard it. I believe they come with an arduino bootloader so you can compile the firmware for the AT90USBKEY (make sure you use the correct mcu part in the makefile; MCU = at90usb1286), and upload the hex file using avrdude for example.

Let us know how it goes :slight_smile:

Oh scratch the Arduino loader part, it comes with its own loader, as of course the connection is usb directly, instead of uart+ftdi. Duh :slight_smile:

awesome! I'm totally about to order a teensy ++ and get a breadboard... RS still sells breadboards right?

Don't forget to post pictures of the finished product once you're done :3