Raspberry Pi launches new product Pico W with Wi-Fi function

Recently, Raspberry Pi released a new RP2040 board with Wi-Fi function. Let's take a look at the highlights of this new board.

Highlights of RP2040

The first chip launched with the Raspberry Pi, the RP2040, includes two Arm Cortex M0+ cores running at 133 MHz and 264 KB of on-chip RAM. The device also supports up to 16 MB of off-chip flash memory via a dedicated QSPI bus.

Raspberry Pico. Image courtesy of Raspberry Pi

A key advantage of the RP2040 over similar products is its programmable I/O (PIO) peripherals, which can be used to implement different digital communication protocols as well as less common protocols such as the WS2812 LED protocol. The company also released the Raspberry Pi Pico, a $4 microcontroller board built using the RP2040 MCU.

A clear drawback and two potential solutions

The Raspberry Pi Pico is a low-cost alternative to the RP2040. It pairs the RP2040 with 2 MB of flash memory and a power chip that supports an input voltage of 1.8-5.5 V. However, the main drawback of this low-cost board is that it does not offer wireless connectivity.

While IoT applications use both wired and wireless connectivity technologies, wireless solutions are often preferred because they simplify deployment and configuration. To add wireless connectivity to IoT devices, we can use wireless SoCs or wireless modules.

Option One: Using a Wireless SoC

While wireless SoCs, such as Texas Instruments' CC3100 Wi-Fi network processor, can be used to add wireless connectivity to IoT devices, SoC-based designs require time, cost, and engineering expertise.

Block Diagram of CC3100

When building a custom RF circuit, many factors affect circuit performance, including board layout and materials, antenna type, antenna trace shape, trace length, component type, and component supplier. Even the placement of board screws and batteries can cause unknown adverse effects. A matching network is also required to ensure that the signal is not attenuated as it propagates between the antenna and the SoC.

The complexity of these RF designs is the reason why experienced RF engineers are expensive. In addition, RF design requires expensive lab equipment and tools. Considering all these obstacles, custom RF implementation does not seem to be a reasonable solution for adding wireless connectivity to low-cost boards such as the Raspberry Pi.

Option 2: Use a wireless module

Another solution is to use a wireless module. Different chip manufacturers, such as Espressif Systems and Silicon Labs, have released many options for such modules. With a wireless module, much of the design is already done.

The PCB has been fully characterized and optimized for RF performance. Antenna layout, shielding, timing components (crystals), as well as regulatory approvals and standards certifications are all completed by the module manufacturer. This significantly simplifies the design process for the project.

Raspberry Pi Pico W has built-in wireless connectivity

Although wireless modules have made wireless connectivity available to engineers and makers, they still require an additional circuit board. To address this, Raspberry Pi recently launched a new version of the Pico board that includes Infineon's CYW43439 wireless SoC.

Raspberry Pi Pico W Wireless Products

The new board, the Raspberry Pico W, is priced at $6. The radio is enclosed in a metal shield to reduce the customer's final compliance costs. The CYW43439 includes the IEEE 802.11 b/g/n MAC, baseband, and radio circuits. The wireless SoC also integrates a power amplifier (PA) that meets the output power requirements of most handheld systems, and a low-noise amplifier (LNA) for improved receiver sensitivity.

In addition to the aforementioned Wi-Fi standards, the CYW43439 also supports classic Bluetooth and Bluetooth Low Energy. Although Bluetooth connectivity is not currently activated on the Pico W board, the Raspberry Pi may include this feature in future versions.

Other RP2040 boards can also be connected

Since the release of the RP2040 in January 2021, a large number of third-party RP2040 boards have been produced by different vendors. Each of these third-party boards attempts to improve upon the original Raspberry Pi Pico board. Among these boards, there are also solutions with built-in wireless connectivity. One example is the Nano RP2040 Connect from Arduino, the functional block diagram is shown below.

Block diagram of the Nano RP2040 Connect. Image courtesy of Arduino

The Nano RP2040 Connect uses the u-blox Nina W102 module to provide Wi-Fi and Bluetooth connectivity. The u-blox wireless module supports IEEE 802.11 b/g/n and Bluetooth 4.2 standards. The module also includes an integrated planar inverted-F antenna (PIFA).

The Nano RP2040 Connect has some additional components such as a 6-axis IMU and an omnidirectional digital microphone. The price of this board is about $30, which is much more expensive than the Pico W board.

Pros and Cons of Wi-Fi

There are several different wireless protocols used in IoT applications, such as Wi-Fi, Bluetooth LE, Zigbee, and Z-Wave. When evaluating wireless solutions for IoT applications, “one size does not fit all.” But what are the pros and cons of Wi-Fi—especially for the Pico W board and some of the other RP2040 projects on the Internet?

Wi-Fi has one standout feature: it is natively IP-based. This is because, from day one, Wi-Fi was created for Internet connectivity as a wireless alternative to the wired Ethernet standard. With this in mind, Wi-Fi is the best choice when we want IoT devices to connect locally to the Internet.

Devices using protocols such as Bluetooth and Zigbee cannot connect directly to the Internet for cloud or remote access. In these cases, a hub or gateway device is required to convert the information from Bluetooth/Zigbee/Z-Wave format to Wi-Fi, which then sends the data over the Internet via a Wi-Fi router. This additional gateway adds cost and complexity to the system.

However, in IoT applications, traditional Wi-Fi has two major limitations: it cannot efficiently support a large number of devices at the same time, and it consumes a lot of power. A recent upgrade to Wi-Fi, called Wi-Fi 6 or 802.11ax, is designed to facilitate IoT applications. Wi-Fi 6 supports crowded IoT networks while consuming less power.