Understanding Hardware Design

As technology becomes more and more complex there is an ever growing need to understand and implement reliable and cost-effective hardware – all to support software expectations. Just a decade earlier it was common for a Hardware Engineer to also be a Software Engineer – and this is still the case of many simple products or when developing hobby level electronics. In this article we’ll go through the method of developing hardware as well as some tips and tricks to ease your development.

What is Hardware Design and Development

Hardware Design and Development relates to the method of implementing IC’s (Integrated Circuits) and Electronic Components into a system, usually in the form of a PCB (printed circuit board). The process involves careful component selection, schematic design and PCB layout/routing. Post manufacturing of the design, hardware verification, validation and testing is completed to ensure the final solution meets all requirements.

Prerequisites for hardware development

None. Anyone can delve into art of electronics hardware design and development! This article will mostly be for the makers and entry level hardware engineers.
For more advanced hardware design usually an Engineering Degree in Electronics or understanding of basic physics and math principles can be helpful – especially for high-speed electronics.

Measuring Tools, Equipment & Software

You don’t need to spend much to get started, less than <$100 should be sufficient.

Measuring Tools & Equipment

1. A low-cost multimeter from amazon or ebay <$25 (No need for True RMS)
2. If your budget allows, then a low-cost USB oscilloscope is also handy <$50
3. Breadboard jumper cables also come in handy for when your PCB is designed, and you want to solder some wires to measure signals <$10

Software Tools

Some free options include, KiCAD, Eagle & EasyEDA. If you are at university then most likely you’ll have access to Altium which is great, however not really required to get started on basic hardware design.

Hardware Design & Development Process

The process for developing hardware can vary depending on design complexity. There are also different project management models that are used to create systems and products, e.g. waterfall and agile etc. Below we’ll focus on a straightforward waterfall type approach.   

Gathering Requirements

Product needs will dictate the selection of hardware. So, the first step is usually understanding what is required at a higher level. Here’s a brief list to go through which illustrates the type of requirements that might need to be gathered:

1. How is it powered? Does it need a battery?
2. Does it need to communicate with the internet to send data?
3. What are the size constraints? Does it need to fit into a pre-existing enclosure?
4. How do you interact with it? Does it need a screen or is it controlled via an app?
5. How will it be programmed? Does it need a special programming port?
6. Where will the hardware be sold? What are the certification and conformance requirements?
7. Is there is a cost consideration? Will it be produced in high volumes?
8. Does it need to be future proofed?

Create a block / system level diagram

Once you have all the requirements it’s time to create a system level diagram, this diagram can be drawn on your PCB design software itself or as a separate document. It should illustrate the high-level design of your hardware. If possible showing where power flows, what communication protocols are used and how they connect from each schematic to another is a great way to start visualizing your hardware design. Here’s an example of how it should look:

Major Component Selection

Selecting major components is based on what the requirements are of your system. It’s important that a buffer is added to ensure the PCB is future proofed. E.g. 20% extra I/O or 50% extra memory.

Detailed Design

Detailed design is where the bulk of the time and resources goes into hardware development. It’s important not to rush designs as unlike software development you can’t just “recompile” a Printed Circuit Board.

Schematic Design and Validation

Schematic design illustrates the connections between circuits and electronic components. Including passives (capacitors, resistors, inductors etc) and active integrated circuits (micro controllers, embedded devices, system-on-chips etc). It’s important to check the schematic carefully as any mistake here will most likely mean you’ll need to re-manufacture the hardware. Here at Elemental Electronics we have dedicated templates to check and validate schematics, which is usually completed by someone other than the main designer.

Footprint design and Development

Electronic component manufacturers usually specify the required PCB footprint for their components. If not available, the IPC 7351 standard is a great reference for ensuring good footprint design. The standard also goes into the different “densities” usually denoted as “Low” “Medium” and “High”. For makers and hobbyists “Low” or “MFG” density will allow for easy manual soldering and repair. 

PCB Outlines and Mechanical Constraints

First thing before laying out any components is to draw the dimensions of your PCB. If it’s going in an enclosure put in the mounting holes and allow for any other mechanical constraints is critical.

PCB Routing

PCB Routing is an art on its own and takes a lot of experience – especially if it’s a high-density board. A good way to start is to route sections off the PCB first separately, e.g. Power Circuits, MCU, input/output connections etc. Then once the sections are completed, place them on the PCB and interconnect the circuits.
It’s also common to begin a design then ½ way through decide to start again from scratch – don’t feel disappointed if this happens it’s all part of the learning process.

DFM and Manufacturing Outputs

PCB manufactures require certain outputs to print and manufacture your board. For a low-cost PCB I would recommend JLC or PCBway, they also have excellent tutorials and guides on steps for creating manufacturing data.
It’s also recommended to check your manufacturing output data as sometimes there can be some discrepancies when generating them, a good free tool to use is gerbv.

Manufacturing & Assembly

Most basic boards and hobby level electronics can be soldered together by hand, with not much more than a basic soldering iron. Assuming you are soldering by hand then we recommend the following approach:

1. All power circuits first
2. Turn the hardware on (only with power circuits)
   • And measure the voltages and make sure there isn’t anything unexpected
3. Start soldering each section at a time
   • First the MCU and circuits required to turn on the MCU
     1. Complete a software check to ensure you can communicate with the MCU
   • Then the rest of the circuits with connectors and larger components last (Unless they are passives)

Testing and Validation

Once a PCB is assembled and manufactured it’s important to make sure that all the initial requirements are met. Usually, hardware level specific testing should also be completed these can include items such as:

1. Voltage level stability/ripple and line regulation
2. POR (Power-on-reset) testing
3. Performance over temperature
4. MCU clock stability
5. Noise on ADC inputs
6. Thermal / temperature testing
7. Unit testing (Stress testing one function)
8. Software/Hardware testing
9. Compliance and EMC Testing

Production Manufacturing & Support

It’s rare for a product to not require some level of support during production manufacturing. From creating a test fixture or ICT (in-circuit tester) to custom flashing software, it’s important to not underestimate the cost and resources to proper setup for production.  Some items to think about for production include:

1. In Circuit Testing
2. Test fixtures
3. EOL (End-of-line) testing
4. Purchasing MCU’s that are already flashed (This can save a lot of time)
5. Component sourcing/purchasing plans and matrices
   • Including alternative components

Top 10 key principles of hardware design

We’ve put together 10 key principles below that we think are critical during hardware design and development. 

1. Major Component Selection

As a beginner select major components that have a good online user base, i.e. ATmega328p (Based on the Arduino UNO) or something from the PIC series.
If in doubt using switching regulators then LDO are a safer option, alternatively purchase DC-DC converter drop in components.

2. Power Management & Optimization

For power critical requirements it’s always good to test as much off-board as possible. Datasheets can sometimes be written to create more sales of a certain ICs. This is especially true for efficiencies of DC-DC converters. We sometimes develop test PCBs just to evaluate PMIC (Power Management Integrated Circuit)

3. Layer Stack up

Layer stack up determines the number of routing layers on a printed circuit board. Beginners usually just required 1,2 or 4 layers. If 4 layers are used, we recommend routing layers on the outer 2 layers and the inner layers to be GND or 0VDC.

4. Thermal Management

Many IC’s especially power related and switching components are limited by their thermal properties. It’s important to go through the datasheets of these components and ensure that sufficient thermal dissipation is designed into the PCB. This could include heatsinks, thermal vias or even active cooling such as fans and liquid cooling.

5. Cost optimisation

For low-volume one-off PCBs looking into cost reduction isn’t worth it. If you are designing a board for larger production volumes, then cost can be optimized by:

1. Design your own DC-DC converters instead of buying off-the-shelf components
2. Reducing number of expensive capacitors (e.g. tantalum or some electrolytics)
3. Reducing the number of layers of the PCB
4. Using lower cost connectors

6. PCB layout techniques

Here are some basic layout techniques that will make designing a PCB a bit easier:

1. Keep enough space between tracks/traces (This also helps with EMC/EMI)
2. Setup your design rules (Use your suppliers capabilities to set these up)
3. Place components in sections
   • i.e. Digital signals in one area and anal og in another
4. Try keep connectors all on one side of the board (i.e. top or left side)
5. Place only low-mass components on the bottom layer (small capacitors etc)
6. Use ground / 0VDC planes

7. Test points

Placing test points that are easy to probe and verify the board is functioning properly is critical – especially for production. You can implement test points by using either pads or through hole vias. Some test points are solderable like the Keystone’s 5012 series.

8. Fiducials and DFM (Design for Manufacturability)

A bare minimum of 2 fiducials are required for each side of a printed circuit board. We recommend using 3 and placing additional fiducials next to high-density ICs. The size of your fiducial is usually determined by the manufacturer of the circuit board, however a general rule of thumb is for the copper diameter to be 1.5mm diameter with mask removed to 3mm.

9. Keeping it simple

Don’t over-complicate the board by trying to squeeze everything into one area for no reason. If you have low-speed signals feel free to use as much of the board space as possible.

10. EMC Considerations

EMC is a complex topic that involves a good understanding of electromagnetics. But here are some generalised rules when designing hardware. Ground and Reference can be used interchangeably. 

1. Place a ground plane directly under your tracks
2. Don’t split the ground plane – unless you really have a need for this, most the time you won’t.
3. Don’t route signals over a “split” ground/reference plane
4. Use ground return vias (place a ground via next to the signal routing tracks)
5. Pour ground on the top and bottom layers. Route triplets where possible (ground between traces)
6. Not-Fit components that might be used to filter. I.e. you might place a PI filter on the power input to an MCU

What’s next for Hardware Engineering?

With technology expanding into different areas such as AI and quantum computing, hardware will only get more complex. User and client expectations also mean that more functionality is required from products – whilst maintained similar size and battery/power usage.

AI Hardware & FPGAs

FPGAs play a critical role in AI hardware. They can accelerate AI computational tasks as they run data streams in parallel (rather than sequentially). This is particularly useful when trying to process data or even graphics. Many FPGAs now come with an MCU on-board, this makes routing and hardware design much easier.

IoT (Internet of Things)

IoT has been around for many years, and the process of developing hardware that is “IoT” enabled is well established. Moving forward, a continued focus on lower power devices and MCUs, battery management and increased functionality within the same hardware package will drive the IoT trend. 

More for less & expectations

Component and chip pricing can be very volatile and depends on many factors including raw material pricing fluctuations, political stability, global demand and logistics. As user’s demand more from their hardware costs are only going to increase (mostly for the high-end components). We should however see costs remain stable for the lower-end 8-bit MCU’s as they are well established and are considered “legacy”. 

Conclusion

Most hobbyists and junior engineers can create simple hardware without the need for advanced knowledge in the field. Practice makes perfect and it can take many years and deep knowledge in Electronic Engineering to create complex high-speed/reliable circuits that are used in a wide range of applications.
Got a hardware idea or a working prototype that you want to refine? Speak to us today for a free quote refine and manufacturing your next product!