The major options
So you want to start developing your own gadget or appcessory connected with Bluetooth Low Energy (BLE), but you are overwhelmed by the many options available. What is a System-on-a-chip and why should I care? Is it the same as an Integrated Circuit (IC)? Should I purchase a module or a development kit?
It all starts with silicon
In the past, silicon vendors mostly designed and offered Integrated Circuit (IC) solutions. That meant you could usually mix and match your preferred or best known chips when designing a new electronic system. For instance, you could add to the design your preferred microcontroller (MCU), communication IC, external Flash storage and other peripheral ICs.
The advantages of the multiple IC approach is that you can create a best-of-breed design leveraging your previous experience with multiple vendor ICs. Drawbacks are that the complexity is bigger (more choices to explore), interoperability issues frequently arise, and the number of components and PCB space will be usually bigger. Drawbacks compared to what? To using a System-on-a-chip (SoC) instead of a collection of interconnected and separated ICs.
A SoC is a single chip where the vendor has packaged all features one will usually need to address a specific market. There are several Bluetooth Low Energy SoCs in the market which integrate in a single chip: one or more microcontrollers, static RAM memory, Flash memory, Bluetooth controller, RF transceiver, voltage regulators and tons of extra peripherals (analog to digital converters, timers, cryptographic processors…)
We have already introduced the first tier (lowest level) of our solution: the “silicon”, either a set of interconnected ICs or a single SoC. But… working with a bare silicon chip means you have to design your own RF PCB, tune the design to comply with electromagnetic compatibility (EMC) and interference (EMI) regulations, debug and iterate through several prototypes, all of which require highly qualified designers and translates into a lot of time, money and resources.
Module vendors to the rescue
One tier above the bare IC or SoC is the module, a small form factor PCB, ready to use, where not only the IC or SoC is already soldered, but also the required RF components (filters, antenna), oscillators and passive components. To top it off, many available modules also include a metal shield to prevent EMI and are certified according to the regulations in place in one or many regions of the world: Europe (CE mark), USA (FCC), Canada (IC), Japan (VCCI)... Modules break out most of the IC or SoC signals, power and I/O ports, for easier integration with your design.
For all the above reasons and depending on the number of units to build, the total cost of embedding a module in your design can be lower than building your own circuit based on a Bluetooth Low Energy IC or SoC.
As a rule of thumb, if you are manufacturing less than 1K-10K units of a product, using a certified module while dodging the complexity of the RF design is the best route to follow. Even if you are into a very competitive market and need to reduce the BOM by a few cents, you can always get into deeper ground after your product is a huge success! Or you may save some cents from another part of the budget (packaging, shipping, handling...)
A last word, specially important for startups, using a ready to use module will surely allow you to get sooner to the market.
Development kits: the lean path to prototyping
To end with this brief overview of options, let’s take a look to the tier with highest level of abstraction: the development kit.
In many cases directly designed (or funded) by the silicon vendors, hardware development kits are intended to ease the learning of the technology. In the case of BLE SoCs, many of them include a hardware module soldered in a breakout board, a hardware programmer and software tools allowing fast prototyping of your firmware (where the real magic and user experience lies in).
In the case of bare ICs or slave SoC modules, a board designed to connect to an external MCU development board is usually provided.
Which approach is the best?
The table below sums up the different approaches you can follow when designing your Bluetooth Low Energy connceted prototype or product. Full disclosure: here at BLECentral we are great fans of certified modules.
This table is not intended to be complete and we will grow it adding more references in the future. Do you miss any? Is your favorite one not listed? Please, tell us!
|Silicon||- Highest design flexibility.
- Cheapest Bill Of Materials (BOM) for >10K units manufacturing runs.
|- Most expensive Non-Recurrent Engineering (NRE) costs: development, design and test of RF PCB.
- Highest complexity. Risk of unexpected delays and high costs associated to EMC/EMI certification.
- Longest time-to-market (TTM).
|- Avoid for small and medium manufacturing runs (<10K units).
- Lowest cost for big manufacturing runs (>10K units).
- Requires highly skilled engineers in the team and/or very expensive design and test services.
- Difficult and expensive certification.
- Slave chip:
- System on a Chip (SOC): Nordic nRF51822, Texas Instruments CC254x
|Certified module||- Fast and lean development path.
- Does not require highly skilled RF/EMI/EMC engineers or external services.
- Fast and easier certification of the finished product.
|- For big manufacturing runs (>10K units) can be more expensive than rolling out your own PCB/RF design.||- Short time-to-market (TTM).
- Greatly empowers embedded system engineers without RF knowledge.
- Fast and easier certification.
|Huamao technology HM-11, BlueGiga BLE112|
|Development Kit||- Shortest development time for prototypes and Minimum Viable Products (MVPs).
- May be used in small manufacturing runs (<100 units) or one time projects.
|- Much more expensive and bulky when compared to the other approaches.||- Allows very fast prototyping.
- Greatly empowers hobbyists and makers.
|Nordic nRF51 DK, Texas Instruments CC2541 Mini DK|