This business card is a demonstration of a production flow of hardware project development. With the process outlined below, I can push the manufacturing documents to a board assembly company in Hong Kong and get five prototypes within one week cost effectively. This process allows for a rapid development cycle that allows a engineer to quickly iterate over hardware, software features and bugs getting prototypes into the hands of users for real world validation testing. The main steps are outlined below:

• Pick Processor
• Draw Schematic
• Source Components and footprints
• Layout Board
• Export pick and place and Bill Of Materials
• Place JLCPCB order, Refine and check bill of materials, check component placements
• Procure through hole or other components for assembly
• write firmware

Processor

The processor on the card is a nRF52832. It is a ARM Cortex M4 processor that has plenty of features with Bluetooth and NFC built in. For this project I just use basic binary general purpose input and output to turn the LEDs on and off and as interrupt pins for button pushes. The full datasheet is below:

Schematic

I use Fusion 360 for designing the circuitry. The nRF52832 datasheet has several reference circuits to get started. The one I used in this project is for low power battery applications. This design is relatively simple. There is the processor circuit, a matrix of LEDs, a few buttons, pins for programming and debugging and finally a battery.

Sourcing Components

I am using JLCPCB.com to manufacture the board. They have a large set of components on hand including our processor the nRF52832. You can globally source other components like DigiKey and Mouser if they don’t stock the component. It takes a week or two for the components to arrive to JLCPCB’s manufacturing plant in Hong Kong. You can search their component offerings through LCSC.com.

The next challenge is to pick components that also have a chip layout and footprint that can be imported into Fusion 360. That is where SnapEDA comes in. SnapEDA has built a plugin for Fusion 360 to import component layouts and footprints directly into your component library. You can create your own custom layouts, but generally I can find what I need through SnapEDA. Also, the Fusion 360 Electronics design system is based off of EagleCAD which Autodesk acquired. So any existing EagleCAD schematic can be imported and the reference circuit can just be copied and pasted into your design.

DigiKey www.digikey.com
LCSC Electronics www.lcsc.com
SnapEDA www.https://www.snapeda.com/

Board Layout

Once you have your schematic completed, you can move on to board layout. Since AutoDesk acquired EagleCAD a few years ago, the modeling and physical layout features have really matured. It is relatively easy to take a drawing from a physical STEP file, create a board outline that aligns with your project, and place the electronic components onto that outline. This project is a business card so it is just a 3.5″ x 2″ rectangle.

There are several design layout specs that are available online that define the manufacuring restrictions JLCPCB imposes. Those specs are EagleCAD/Fusion 360 compatible and can just be imported to check your layout for any possible issues. https://github.com/oxullo/jlcpcb-eagle

JLCPCB can manufacture a 5 board single sided populated, 2 layer PCB very economically. I try to keep all the surface mounted components on one side of the board, and place any hand soldered components on the other. In this design the processor, LEDs, capacitors, buttons and resistors are on one side, and I just need to solder on battery holder on the bottom.

Pick and Place Manufacturing Files

Once, the board layout is completed the manufacturing files need to be exported and uploaded to JLCPCB. The layout and pick and place information can be exported directly out of Fusion 360. The bill of materials can be exported via a script from github.

https://github.com/oxullo/jlcpcb-eagle

The layout and pick and place can be uploaded to JLCPCB without any alterations, the bill of materials needs to be looked over before manufacturing begins.

JLCPCB Ordering and Manufacturing

JLCPCB offers bare PCB manufacturing and assembly services as well as 3D printing services. An assembled board and 3D model can be built within 3 days then shipped via DHL and be in my hands within 3-5 of travel time. That means I can put an order in on Monday and have the parts of a prototype in my hands the following Monday. They offer a wide range of components through their LCSC partner website. If you have a specific component need you can order the part from DigiKey, Mouser or another component warehousing provider through their web portal. It takes 8-10 days to get to Hong Kong, but they will maintain and store your parts for you until you are ready to use them in a design.