Most everyone, at some time, has heard the term “The Internet of Things”, or more commonly referred to as the IoT. The IoT describes how physical objects are slowly connecting to the internet, a simple example being your thermostat at home that can now be controlled via your cell phone through the internet. It’s estimated that 6 billion such everyday physical objects will be connected to the IoT by 2020. This means that the IoT is not just a fad or a market trend, but a real commercial reality with a lot of money involved in it. Sensor-based systems connect the real world to the IoT. These systems must operate interactively with each other, as well as autonomously, and they typically do so using wireless communication. These sensor-based systems for the IoT must also be very low power so that they can run on batteries for a long time.
Bluetooth® low energy, or BLE, has now become the de facto standard for low-power wireless in the IoT market. Over 1.2 billion Bluetooth Smart Ready products were sold in 2013 alone. These include products like the iPad, iPhone, MacBook, Android and Windows phones, and also laptops and desktop computers, which essentially means that you have a whole ecosystem of hosts to connect to very easily. In addition, BLE is designed for low-power sensor-based products like wearable electronics, medical devices and home automation devices. IoT products require sensor-based BLE systems.
Figure 1 shows a few examples of IoT products. The first one is a fitness monitor by Jawbone, which is an example of a wearable electronic device, the second is a heart rate monitor by Mio, which is a great example of a medical device, and a third example is the Kevo Deadbolt by Kwikset, which is a home automation device, that connects to the internet and allows you to interactively and remotely unlock your door.
Figure 1: Example IoT devices.
PSoC enables low-power designs due to its architecture. PSoC is the world’s first programmable, embedded design platform. It includes a CPU, like the 32-bit ARM Cortex-M0 for instance, and has both analog and digital programmable blocks. Because of this, it accelerates system design with reliable and easy-to-use solutions such as touch sensing.
Let’s face it, designing wireless sensor-based systems for the IoT is difficult. This is because designing such systems requires engineers to work with multiple design tools from multiple IC vendors. Implementing wireless itself is pretty complex because of complicated specifications like the BLE protocol stack, for instance; and when you get down to the board design, doing RF board design is not very easy, it’s a complicated process as well. Designing systems with multiple ICs increases your BOM cost. When designing these sensor-based systems for the Internet of Things, you will typically require analog frontends for sensors, digital logic for control, a Bluetooth energy radio, and an MCU. Additionally, if you’re trying to create a sophisticated user interface, you might require an additional touch or display IC. All of these quickly add up to your system BOM cost. Finally, achieving low system power is difficult. These wireless systems for the IoT are often operating off of coin-cell batteries and optimizing the entire system’s power consumption requires very careful use of low power modes.
PSoC 4 BLE solves these problems by:
- Enebling complete system design in PSoC Creator
- Simplifying the BLE Protocol Stack and Profile configuration with the easy-to-use BLE Component
- Simplifying RF board design by integrating the Balun
- Integrating programmable AFEs and digital logic, and CapSense with the ARM Cortex-M0 CPU and BLE radio
- Delivering five flexible, easy-to-use, low-power modes
PSoC Creator enables complete system design all in a single tool. What you see in Figure 2 is a Bluetooth low energy heart rate monitor, for example, that implements a custom AFE shown in PSoC Creator. You start off by exploring the library of over 75 components and you drag and drop these components onto your schematic to complete your hardware system design. In this case we’re using a combination of analog components to design an AFE and also the BLE component to provide wireless communication. You would then configure each of these components using the component configuration tools; and each of these components also have their own data sheets that provide you with more information and list out all the APIs, which you can co-design in your application firmware and hardware in the IDE concurrently. Cypress also provides documentation like App Notes. The “Getting Started with PSoC BLE” App Note is a great one that helps you get started with the solution and provide system guidelines for the design.
Figure 2: BLE heart rate monitor example project.
The BLE component itself simplifies the Bluetooth low energy stack and profile configuration. What you would typically do in hundreds and hundreds of lines in code can now be done in a simple, intuitive, easy-to-use graphical user interface. The BLE component in PSoC Creator contains the Bluetooth 4.1 specification, it also contains the BLE Protocol Stack, including all of the supportive BLE Profiles, and has very easy and simple to use APIs for firmware development. If you may recall from earlier, you can right click the BLE component in PSoC Creator to open its configuration tool. In the profiles tab screenshot (Figure 3), you can see how it includes profiles for a heart rate measurement that can be clicked. The figure also shows all of the various parameters available for very easy configuration for the protocol Stack and the profile set up.
Figure 3: BLE component configuration tool.
PSoC 4 BLE also simplifies RF board design. Designing an antenna matching network (AMN) is not very easy, it’s a non-trivial job. This is because these AMNs are sensitive to PCB layout and parasitics and you need to tune it for the best RF performance. The tuning of the antenna matching network increases while the complexity of tuning increases dramatically when many external components are used. A typical AMN uses up to nine external components, whereas Cypress’s AMN only uses two because the Balun is integrated. Figure 4 is an example with Cypress’s solution. You only have to use two external components - an inductor and a capacitor, whereas with Nordic you have to use seven external components, and with the TI solution you have to use nine external components. The PSoC 4 BLE integrated Balun simplifies your RF board design and reduces PCB footprint. Of course it also reduces your BOM cost because you do not have to go buy external components or an external Balun IC.
Figure 4: PSoC 4 BLE simplifies RF boards.
PSoC 4 BLE integrates programmable AFEs, programmable Digital Logic, and CapSense all in a single chip. The integration of all of these blocks together reduces your system’s BOM cost. You can use the programmable analog blocks like the opamps, comparators, ADCs and DACs, to create your custom AFEs for analog sensors. You can use the programmable digital blocks such as the Timer Counter PWM, the Serial Communication blocks, or even the UDBs (Universal Digital Blocks), to integrate digital logic. Additionally, you can implement reliable and sophisticated user interfaces with Cypress’s industry-leading CapSense technology.
In addition, PSoC’s programmable architecture offers some very unique advantages. Firstly, you are able to reduce the power consumption for battery-operated applications by offloading CPU tasks to the UDBs. This greatly saves you CPU cycles. You can also create custom digital peripherals using the UDBs; we’ll show an example later where I’ve put a customized I2C wake-up chip from accelerometer input. You can also reconfigure these blocks during run time or during operation to create multiple functions, thereby allowing you to use the same block to do different things. Of course, with PSoC’s flexible architecture you can use any pin on the chip as an analog or digital I/O because of the on-chip multiplexors. What we have in Figure 5 is an actual PSoC Creator schematic that shows a complete production design for a full system. Starting from the left I have inputs from electrodes from my heart rate monitor, these go to my analog front-in that’s created using four opamps. A couple of these operate as an instrumentation amplifier, whereas another one operates as a filter. Once a signal is conditioned using the analog front-in, it then goes into the 12-bit SARADC. We’ve also added an accelerometer using a customized component, a CapSense component to provide a user interface, a PWM component that could drive LEDs, a segment LCD component to drive displays, and of course the BLE component to provide Bluetooth low energy wireless communication. You can see how you can do this entire design all in a single chip and all with a single tool using PSoC Creator, allowing you to create complete systems for the IoT.
Figure 5: Complete IoT system design.
PSoC 4 BLE also enables very-low-power wireless systems and it does so because it offers five very flexible power modes, namely the active, sleep, deep sleep, hibernate, and stop modes. The details are listed in the table in Figure 6.
PSoC 4 BLE has the best-in-class low-power modes. In the hibernate and stop modes it is consuming the lowest current; 60 nano-amps in stop mode, 150 nano-amps in hibernate mode. It also retains the SRAM data in the hibernate mode while retaining complete system status in the deep sleep mode. PSoC Creator also provides you very easy-to-use APIs to switch easily between these low-power modes, and for a one-second connection interval, which is a Bluetooth low-energy spec, PSoC systems consume an average of 18.9 micro-amps of current. This is because the chip is active for very short periods of time and can go to sleep or deep sleep for the remaining duration.
Figure 6: Complete IoT system design.
Now let’s take a quick look at the PSoC 4 BLE chip (Figure 7), what type of applications it will be used for, and what features it has. Target applications for PSoC 4 BLE include sports and fitness monitors, wearable electronics, medical devices, home automation solutions, game controllers, and any general sensor-based low-power systems for the IoT. As I mentioned, this is the 32-bit ARM Cortex-M0 CPU clocked up to 48 MHz. We will offer parts that do up to 256 kb of flash and 32 kb of SRAM. You have four opamps that can be configured as PGAs, comparators, filters, and then the one 12-bit, 1-Msps SAR ADC. These analog components will allow you to create your custom or programmable AFEs. Of course we have CapSense with SmartSense Auto Tuning included.
This part offers the ability to do touchpads and gestures via the CapSense component. On the digital side we have four UDBs, four TCPWM blocks, two serial communication blocks that can be configured as I2C master or slave, SPI master or slave, or UART. The part is available in two packages, the 56-pin QFN and a 68 CSP. Most importantly, PSoC 4 BLE provides Bluetooth Smart connectivity with the Bluetooth 4.1 specification and has an integrated BLE, 2.4 GHz radio and an integrated Balun.
Figure 7: PSoC 4 BLE CY8C4xx7-BL.
Figure 8 is a solution example using the PSoC 4 BLE chip. In this solution we’ve designed a wearable fitness monitor, very similar to something you’d see from Jawbone. In this particular solution we wanted to try and add BLE connectivity to a sensor hub, interface with multiple analog and digital sensors, drive a PWM-based vibration motor, and do this all with very low power consumption because I want to run this product from a coin-cell battery. So PSoC 4 BLE allows you to do this very easily with a simple one-chip implementation for BLE connectivity. Using the analog frontends you can create the sensor interfaces for your sensors like temperature, humidity, pressure and battery voltage. We’ve implemented a custom AFE using all the programmable analog blocks, with the IDAC acting as a current source, all feeding into the flexible analog MUX which in turn sends everything on to the SAR ADC. I can also interface with additional sensors like an accelerometer using my digital SCB, and of course I can drive a vibration motor using a PWM component and communicate with a Bluetooth Smart-ready host using the BLE subsystem. So, you see how a single chip integrates the MCU plus the AFE and the Digital Logic, plus the BLE radio, all in a simple and very easy-to-use solution.
Figure 8: Solution example – wearable fitness monitor.
In summary, PSoC 4 BLE enables complete system design in PSoC Creator, simplifies the BLE Protocol Stack and Profile configuration with the easy-to-use BLE Component, simplifies RF board design by integrating the balun, integrates programmable AFEs and digital logic and CapSense with the ARM Cortex-M0 CPU and BLE radio, and delivers five flexible, easy-to-use, low-power modes.
References
- Cypress Semiconductor/PSoC 4 BLE (Bluetooth Low Energy) PTM
