02-03-2021 | | By Robin Mitchell
Recently, the Raspberry Pi Foundation announced the release of their latest system, the Raspberry Pi Pico, that could challenge the microcontroller market. What is the Raspberry Pi Pico, what is the chip that powers it, and what features does the Pico have?
The Raspberry Pi range of computers has proven to be extremely popular with most involved with electronics. Makers make use of the Raspberry Pi to help simplify advanced projects or as a stand-alone computing system while professionals can utilise the Raspberry Pi as a testing platform.
However, one of the Pi's biggest disadvantages has always been that it is a hybrid between a full-fledge computer and a microcontroller. While the Pi can be used in some microcontroller applications, it is often either too expensive or lacks the I/O speeds needed to be practical.
When it comes to computing applications, while the Pi can provide a user with a cheap computing platform, the price per MIPS leaves it significantly behind a standard PC. For example, a Raspberry Pi cluster can be used to create a home web server, but a second hand server rack can be purchased for the price of two Raspberry Pi’s while having 16 cores, 32GB of RAM, and faster internet connections.
With the desire for a cheaper Pi platform that can enable high-speed I/O, the Raspberry Pi Foundation has recently announced the Pi Pico's development, and the SoC that powers it.
The Raspberry Pi Pico is a Raspberry Pi microcontroller development board that integrates a USB connection, the main SoC, memory, and other needed components for the board to function. Arguably similar to the PyBoard and micro::bit, the Pico can be programmed directly over USB (as it is recognised as a storage device where compiled code is dragged to), and provides a button on the board for entering programming mode.
The Pico has multiple connectors around its edge, allowing for both pin headers (when used on a breadboard) and directly soldering to a PCB with the castellated holes. This makes the Pico practical for both prototyping and for use in a commercial product. The soldered connection forms a reliable bond between the Pico and the board holding the Pico.
At the heart of the Pico is the RP2040, a totally customised SoC designed and developed by the Raspberry Pi Foundation. All Raspberry Pi systems take advantage of SoCs that integrate a processor, graphics, and other needed units to create a computing system, but such devices are not appropriate for microcontrollers.
Such SoCs are far more expensive than a typical microcontroller core, and those costs are passed onto the resulting design. Secondly, such SoCs consume far more power when compared to microcontrollers (watts compared to milliwatts). Thirdly, SoCs used in single-board computers contain unnecessary hardware for microcontroller applications such as floating-point units, graphics processing units, and cryptographic hardware.
The RP2040 integrates a dual-core ARM Cortex-M0+ that is clocked at 133MHz and is connected to 26KB of on-chip SRAM. The RP2040 can support up to 16MB of an external flash. While this may sound small, it is important to note that the RP2040 is for microcontroller applications instead of standard computing applications. The RP2040 integrates all the typical hardware used in a microcontroller application including I2C, SPI, UART, Timers, RTC, ADC, and GPIO. Still, the difference between these peripherals and a typical Raspberry Pi is that these can be accessed at full speed with little latency.
The first feature that stands out most about the Pico is its price; $4 for a complete Pico board ready for use. Considering the microcontroller's capabilities, such a price that includes a USB connection and hardware for programming makes the RP2040 highly ideal for most projects.
The second feature that stands out of the Pico is its processor, the RP2040. The SoC was developed in-house by the Raspberry Pi Foundation and appears that it will be available to customers as a stand-alone IC. The documentation for the RP2040 exceeds that of most chips on the market, and the simplicity of use enables for the creation of simple to program and use products.
If the Pico itself can sell for just $4, then it goes without saying that the RP2040 could sell for under $2 which would make it an extremely cost-effective microcontroller considering its USB programming capabilities and minimal hardware needed to get it to function.