EYE ON NPI - EYE ON NPI - Raspberry Pi RP2350A and RP2350B Microcontrollers

Adafruit Industries

For this week's EYE ON NPI, we'll Hazard a guess that you'll be excited to see the Raspberry Pi RP2350 chip available for purchase at Digi-Key for integration into your next design. We've been working with this chip for a few months and it's quickly becoming our favorite Arm Cortex chip, with fun peripherals and a well-supported toolchain. It also is one of the first mass-produced RISC-V chips: one that you can buy and start using for trying out RISC-V development without the 'risc' of worrying you may have picked the wrong core. Available in two chip sizes and with a boost in performance and peripherals, the RP2350 (https://www.digikey.com/short/mzpjhptm) represents a big upgrade to the RP2040 (https://www.digikey.com/en/products/detail/raspberry-pi/SC0914-13/14306010) that you've seen take over the microcontroller world over the last 4 years. Raspberry Pi is famous for their single board computers (https://www.digikey.com/en/products/filter/single-board-computers-sbcs/933) so much so that they created a full market for sub-$100 all-in-one PCs. The big disruption we feel they brought to the market was the creation of a hackable and open-source ecosystem with good main-line OS and driver support. With well-written documentation and up-to-date Linux software, purchasing a Pi meant you got to join in with a community that was having fun, not struggling with compiling out-of-tree kernel modules and closed-source firmware. So in 2021 when they announced the RP2040, folks were interested: could a SBC maker design low power silicon? Turns out, yes! The RP2040 was a fun dual-core 133 MHz Cortex-M0+ processor, with 264K of SRAM, with a satisfying collection of peripherals: USB, ADC, UART/SPI/I2C, PWM, DMA and timers plus the nifty PIO state machine (https://www.raspberrypi.com/news/what-is-pio/). The killer feature, though, was the price: at $1 a chip, and tons of availability with an on-going chip shortage, the RP2040 won our hearts and soldering stations! Three years later, Raspberry Pi is back with a sequel: The RP2350A (https://www.digikey.com/en/products/filter/microcontrollers/685?s=N4IgTCBcDaIE4AcwGYCsAGAgiAugXyA) and RP2350B (https://www.digikey.com/en/products/filter/microcontrollers/685?s=N4IgTCBcDaIE4AcwGYCsAGAQiAugXyA) two variants of an upgrade chip that keeps what was great about the '2040 but with some boosts. First up, the core was upgraded from dual Cortex-M0's to the M33: this means you get an FPU and better low-power performance, plus TrustZone security. The core is spec'd for 150MHz but we've overclocked it to 264MHz without too much complaint. You also have the option to get dual RISC-V cores (https://riscv.org/) instead. SRAM was also bumped: from 264K to 520KB. This is great for running interpreted languages like MicroPython (https://micropython.org/) or CircuitPython (https://circuitpython.org/). Like the original, the RP2350 does not have any built in FLASH memory. Instead, you will need to wire it to a QSPI flash memory chip (https://www.digikey.com/short/80t4zt5t). This way you can pick from 1 MBytes to 16 MBytes whatever your code size needs. This new chip adds the ability to wire in PSRAM (https://www.digikey.com/short/d8033bfw) to the same QSPI bus plus an extra chip select. This is not going to be nearly as fast as on-chip SRAM, but it's great when you want large working memory that the chip will manage for you: by configuring it in the CMakefile, you 'magically' get a huge area you can malloc. Another improvement is in the number of PIO blocks: the original had 2, the RP2350 has 3. The two biggest new features we found are the new HSTX peripheral and the 80-QFN RP2350B (https://www.digikey.com/en/products/filter/microcontrollers/685?s=N4IgTCBcDaIE4AcwGYCsAGAQiAugXyA) variant. HSTX stands for High Speed Transmission and its a high-speed peripheral that can drive 8 output lines - note that it's output only! There's a few possible use cases, but the core reasoning is that this lets you control a DVI display directly from the chip using just the DMA and internal memory without requiring overclocking, PIO, or an extra core. Note that the built in SRAM limits the size of the display if you want to have a video buffer: you can do 320x240 @16bpp or 640x480 @8bpp but, still! Second, if you found the original QFN-60 a bit constraining in terms of GPIO, the QFN-80 'B' version has 20 extra GPIO available for just 10 cents more. If you've been doing grabby-hands in hopes of getting a reel of RP2350 chips into your next design: today is your lucky day! Digi-Key has these chips in stock RIGHT NOW for immediate shipment. You can get a reel of either A or B type chips, with cut tape individual components coming shortly. Both types are great, but recently we've been having a lot of fun with the roomy B type (https://www.digikey.com/short/mzpjhptm), with the extra GPIO. Order today and you can start integrating the trendiest new silicon into your new PCB assembly by tomorrow afternoon.