USB Serial Uart With Kicad

As I begin to consider my next project I first need to do some research and better yet some testing. You see the upcoming project I have in mind will require a on board serial usb connection..

After spending what seemed like weeks pouring over data sheets from all the major players I settled on two chips. Both from Microchip! The one I decided on was the MCP2221 usb to serial uart chip.

Around the same time I started to dive in to Kicad. This was a new pcb software for me. I have heard about it in passing but up to this point have not tried it. For this board I decided to change that and go ahead and design a usb serial uart board to test my chip choice for the up coming project. Install went without a hitch. Within seconds I was navigating the interface and doing my best to learn my new tool.

I must confess the learning curve while not bad at all; it did pose a hiccup or two. I had to “Rethink” or should I say “Relearn” my approach to libraries. Kicad does this differently then I was use to. But documentation and help have been plentiful before long I was on my way creating my own libraries and modifying footprints to suit my needs.

After a while I had my project complete and was ready to export the gerber files.

serial board 01

With kicad you can even 3d render your pcb! Wow, how cool. Now you can fully review your pcb as if you had it in hand before even placing your order!

serial board 02

Of course I had to modify the pcb solder mask colors to match my pcb house of choice. Shout out to OSHPark They make a excellent product with fast turn around. Perfect for the small batches of boards I need..

Going over my order sheet. It looks like I had the boards in hand in under 2 weeks. Not bad at all!

Ordered on: October 22nd 2016
Shipped on: November 2nd 2016

serial board 03

The one thing to keep in mind with Oshpark orders is board clean up. You will have to snip off the extra “ears” around the board. Not a difficult task but one to note..

Next I needed to order the parts to assemble my new pcb boards. Back to the Microchip datasheet. Wait a moment. It looks like a newer chip just came out from them that was not available when I designed my board. I quickly downloaded the new data sheet. Nice! this new chip is a drop in replacement for the chip I designed for. The new chip I am going with and need to order is the Microchip MCP2221A..  I also placed my order for the remaining parts.

serial board 04

Assembly went smooth without to much complaint. I do need to pickup a set of helping hands I think!

serial board 05

If you head over to my Instagram page you will see my first test video. By connecting the rx and tx lines with a jumper I was able to echo back what I sent out to make sure the board functions as expected. Awesome!

My next test was more practical. I hooked it up to one of my Uno clones and proceeded to flash a new sketch onto the Uno. I do have to manually press the reset switch right before upload as the mcp2221A has no hand shaking line. but this was no real problem. Success! The new sketch loaded right away.

Conclusion? I will say this is a success. I will be moving forward with this chip in my up coming project. For now if you would like to help support projects like this and more content in the future. Please feel free to head over to my Shop Page and pick one up for your self. You deserve it! 🙂


serial board 00