USB to atmel

Hello Everyone,

I am finally getting my circuit off of the arduino and am using eagle to lay out a pcb.

I have a few questions on how to properly set up the USB to atmel connections.

  1. I have seen many diagrams and breadboards that do not use any resistors or ferrite beads. They work, but I have feeling I should have some sort of resistors, caps and a bead to help with noise, Fluctuations with voltage, that type of thing.

The circuit works great on a breadboard. I have concerns thou when it gets to a pcb.

What is the proper way of going from the USB header on the board to the atmel? In terms of components And layout?

Any help is greatly appreciated! Thank you

questions on how to properly set up the USB to atmel connections.

All of the production Arduino boards have schematics and reference designs. Below is the UNO... should give you all the basics by following the originals:


Could also follow the chip maker's guide for the USB/Serial chip. for FT2323RL and similar chips. Here for the Atmel chip Atmega16U2, Section 20 for USB.

I've laid out a few boards with the FTDI chip, there are no special things to worry about, just the normal decoupling and take note of the components used in other designs.

I do use traces with rounded (or no) corners, but that's not really required I think. Just don't run D+ and D- clear across the board, keep them short.


Thanks for the replies!

On the ferrite bead, I have been doing some reading about these. My understanding is that these are basically a jumper wire that is coated with some material?

Would this part work for a bead for USB?

I was looking at the datasheets for these parts and am curious. Is the current the biggest concern? If so I would assume that I am just looking for a part that is ok for 500mA for usb use?

Lots of production merchandize use these to get through FCC certifications. For hobby use, they are rarely needed. Use them at your own discression... Or, buy them by the lot and make geek necklaces for your friends.

Seriously, they are useful, but placement is everything. Unless you understand the nuances of RF noise suppression or unless a design calls for them, you can generally ignore their value.