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• Version 0.2 - 2-layer board

  Andrew Retallack • 03/13/2014 at 12:16 • 0 comments

  A Two-Layer Breakout

  We were happy with our one-sided self-etched board as a proof of concept, and were now ready to move onto something that would approach a final product. We made a number of changes to the design, which meant we needed to move to a two-layer PCB:

  • Power: We made the power more accessible. Instead of presenting VCC and GND as separate female pins on the board, we chose to drive them straight into the breadboard
  • ICSP Header: it’s great to be able to program using an FTDI chip, but it’s harder to burn bootloaders and set the fuses on the chip, so we included an ICSP header
  • Silkscreen: Of course we can’t have a cool looking silkscreen on our self-etched board.
  • SMD Components: If you’re playing with microcontrollers on breadboards, you’re probably adept enough at soldering to handle a few larger SMD components – we therefore included a few 1206 resistors and capacitors, as well as a LED. They’re fun…

  Building a professional prototype PCB

  After a load of research, and hearing of them on a few respected posdcasts, we uploaded our EagleCAD .brd files to OSHPark. They are extremely competitive, turnaround times are good for our purposes, and it’s great to support a small company. The render of our board is shown in this post.

  OSHPark kept us in the loop, and the boards were shipped. The wait was nearly over – we couldn’t wait to get a purple PCB in our hands!

• Version 0.1 - the Birth

  Andrew Retallack • 03/13/2014 at 12:15 • 0 comments

  My RF Project: The Problem

  I was working on a low-energy RF project, using the HopeRF RFM12B. I was going to start out by prototyping using my Arduino UNO, but hit a few problems:

  1. The RFM12B works at a maximum voltage of 3.8v – the UNO runs at 5v
  2. I only had one UNO, and I of course needed two controllers to establish communication.

  Easy, I thought. I’ve built an Arduino on a Breadboard before!

  So I built my two Arduinos on a Breadboard, using 3.3v regulators to remain within the RFM12B spec. It was a struggle to work through the jumper wires, but I managed to get the test up and running, and had the two modules communicating. OK, so the principle works, now let’s wire up a few buttons, a temperature sensor, and a few LEDs. I also only had one FTDI board to program the microcontrollers, which I was repeatedly unwiring and rewiring. I now had a mass of jumpers, and couldn’t see the forest for the trees. It was time to re-think things.

  A Microcontroller Breakout: The Solution

  What I needed was a way to connect my ATmega328P to the breadboard:

  • without all of the clutter of the supporting components and wires
  • without rebuilding a power supply again and again
  • with the ability to choose between 5v and 3.3v
  • with the ability to program using my FTDI without re-wiring

  Version 0.1: A self-etched PCB

  The first stage of the project was to develop a prototype that could be easily and quickly tested and tweaked. The key focus was to test the footprint of the board, as well as of course the functionality. This was achieved using the toner-transfer method to create the PCB image on a copper-clad board, and then to etch, drill and solder this manually.

  The first version of the PCB worked well, but of course we picked up a few items to tweak and refine. Once that was done, we were ready to move onto the next step – a two-sided PCB with additional functionality.

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