nRF5x SoC Overview
The Nordic Semiconductor nRF5x System on Chip (SoCs) are ideal for ultra-low power (ULP) and cost effective short-range wireless solutions. Typical applications for the nRF5x SoCs are Internet of Things (IoT) devices, wearables, smart home, wireless mobile phone accessories, PC peripherals, beacons, Bluetooth-enabled consumer electronics in general, human interface devices, sports equipment, medical equipment, security and smart toys.
The nRF5x supports Bluetooth Low Energy (BLE), (which was initially advertised under the name Bluetooth Smart), among other short-range wireless protocols such as Thread and Zigbee (on the 802.15.4 MAC), ANT, and 2.4GHz Proprietary. The focus of this course is on Bluetooth Low Energy / Bluetooth 5. Bluetooth Low Energy offers down to 1/10th the power consumption of the regular classic Bluetooth. What made these SoCs so popular is that they can be operated over long period of time (months and even years) on a small battery such as a coin cell battery when properly configured and operated.
Available Chips Options
There are three series in the nRF5x SoC family. The first is the nRF51 series which was introduced in 2012, and had a great success in the market. The second series is the nRF52, which is upping the game, more advanced, and relevantly newer than the nRF51. The nRF52 has extra features, more computational power, more Flash/RAM, and even lower than its predecessor in power consumption, however, when it comes to cost ; the nRF51 has the advantage here. nRF53 series is out of the scope of this course.
The key performance/features differences between the nRF52 and nRF51 series are highlighted in the following table:
A more detailed comparison between the two series is shown below:
Bluetooth 5 is a standard officially adopted by the Bluetooth Special Interest Group (SIG) in December 2016. In summary, the standard has introduced three new main features :
- Double the speed (2x): theoretically, you can send the same BLE data in half the time, hence reduce the radio ON time, therefore reduce the power to half. This is supported in all nRF52 series by the 2Mbps BLE physical layer (2M BLE PHY).
- Support for Bluetooth long range mode ( aka : Full-House coverage mode ): Of course, this is on the expense of throughput ( 125 or 500 Kbps ). This is supported in most nRF52 series SoCs through the long range BLE physical layer ( CODED BLE PHY ) as we will see in Lesson3.
- Support for advertisement extensions: This is similar to the original broadcast role seen in Bluetooth 4.2, but with much higher throughput.
Note: The first and the second feature can not be supported simultaneously in a single device role.
It’s worth noting that on January 28th 2019, the SIG released a new v5.1 version of the Bluetooth Core Specification supporting another new BLE feature called Direction Finding. This feature enhances location finding which is only beneficial for products utilizing BLE for location finding like: asset tracking, points of interest, and indoor navigation.
The nRF51 has four SoC chips options with different package options as shown below:
On the other hand, the nRF52 series has seven SoC chips options.
Originally, the nRF52 series had only three options. The fourth addition to the nRF52 series, which is the nRF52811 chip was introduced in late February 2019 as a response to the release of BLE 5.1 with its new feature of Direction Finding. Direction Finding is an optional feature that provides a better accuracy in terms of close-proximity location finding than the old method of relying on the received signal strength indicator (RSSI). Direction Finding relies on the phase rather than on the power(strength) of the received signal.
The fifth addition to the nRF52 series is the 5.1 BLE-capable nRF52833, which was introduced in October 2019. The new feature offered in the nRF52833 is the extended operational temperature range of ( -40 to +105 C) as compared to the standard (-40 to +85 C) operational temperature range for the other nRF5 SoCs. The sixth addition to the nRF52 series is the nRF52820, which is a baseline(economy friendly) SoC with extended operational temperature range of ( -40 to +105 C) and built-in USB. It was added to the series in March 2020. The seventh addition to the series is the nRF52805, which was introduced into the series in June 2020, offers an extremely cost effective solution on the expense of limited functionality.
The nRF5x SoCs are all-in-one solutions, with both flash and RAM memories embedded inside the same SoC die. Being a flash-based SoC, this means that the firmware will be residing on a flash memory inside the SoC itself. When compared with other alternatives like ROM or OTP SoCs, flash-based SoCs are easier to work with, and allow update/patch firmware in the field. The nRF5x family support secure Over The Air Device Firmware Update ( OTA-DFU ). The entire firmware and/or communication stack updates are possible in the field, which makes these chips quite flexible and future-proof.
Again, the RAM memory is also hosted in the chip die. nRF52 and nRF51 chips differ in the available hardware peripherals and the available RAM and Flash memories as summarized in the tables below :
The figure below shows a generalized and simplified diagram for an nRF5x SoC where peripherals are logically grouped into related units.
In general, a typical nRF5x-based BLE device(system) will have, in addition to the core nRF5x SoC, the following components external to the nRF5x SoC :
- A BLE antenna, which is an external component that could be a PCB antenna (the common case in BLE, and the case of all the official nRF5 Development Kits), or a chip antenna.
- A matching network (capacitors and inductors) to match the nRF5x SoC impedance with the BLE antenna impedance, and also to filter harmonics.
- A high frequency and low frequency crystals required for the on-chip oscillators (inside the nRF5x SoC). The low frequency crystal is optional, however, strongly recommended for power saving.
- A decoupling capacitors and inductors for the on-chip voltage regulators (inside the nRF5x SoC).
- A power source. This could be as simple as a single non-rechargeable coin cell battery like the CR2477 or the CR2032. Or, it could be a rechargeable Lithium battery with an appropriate battery charging and battery monitoring circuitry. Or, it could be an advanced system that incorporate several conventional and non-conventional sources of energy.
- Application-related sensors, actuators, and interfaces.
- An optional NFC antenna for secure out-of-band BLE pairing(nRF52 series only).
The nRF5x SoCs comes in a number of package variants (aQFN, QFN, CSP-WLCSP, and TCSP ) and with different PINs counts, dimensions and pitch length to match a broad range of constraints and applications.
In the next two lessons nRF51 architecture and nRF52 architecture, we will examine these two series thoroughly to get a clear idea of whats under the hood, examine available analog and digital I/O and interface, available system peripherals ( timers, counters , etc..) and advanced radio and power saving features. In addition to listing the official developing boards to start developing products using these powerful SoCs right away.
Enroll to the to the Nordic nRF5x BLE In-Depth Training Course (Foundation Level) to access full materials.
References and pictures:
Nordic Semiconductor http://www.nordicsemi.com