David Johnson-Davies Brings Espressif's Powerful ESP32-P4 to the Feather Form Factor

David Johnson-Davies has released the design files for a compact Feather-format development board built around Espressif's ESP32-P4 system-on-chip — delivering two RISC-V cores running at up to 400MHz, 32MB of pseudo-static RAM (PSRAM), and up to 32MB of external flash.

"After designing the AVR128DA32 Feather Board I read about Espressif's new ESP32-P4 processor, a high-performance processor with a RISC-V core, and decided it would be an interesting challenge to design a Feather-format board based on that," Johnson-Davies explains of the project's inspiration. "Like other recent ESP32-series chips the ESP32-P4 includes an internal native USB interface, so I decided to design the board to support USB via a USB-to-serial chip as well as this native USB."

"I underestimated how much harder this board was going to be compared to the earlier AVR128DA32 Feather Board," Johnson-Davies admits, "and I soon realized that it would only be possible by changing to using 0402 resistors and capacitors, rather than the 0805 ones I was using, and by switching to a four-layer board. Switching to a four-layer board really made the layout much easier. The ground plane layer makes it unnecessary to think about routing the ground, apart from placing vias to connect through to it. Also, the third layer makes routing the power supply connections much easier."

The board itself is designed in a breadboard-friendly gumstick form-factor based on the Feather specification, with a a few modifications: there are two extra pins to provide access to the data lines from the Espressif ESP32-P4's on-board USB peripheral, there's a 1.2V power output, the GPIO22 analog input is dedicated to battery voltage monitoring, and there's a boot-selection button for program upload.

The finished board includes two 32-bit RISC-V cores running at up to 400MHz, 768kB of static RAM (SRAM) plus 32MB of pseudo-static RAM (PSRAM), and up to 32MB of off-chip flash storage. There's a USB connection for power and data, plus a connection for an optional lithium battery complete with charge-handling circuit. What there isn't, however, is any wireless connectivity: while Espressif may have made a name for itself in wireless microcontrollers, the ESP32-P4 focuses on performance — at the cost of excluding any built-in radio hardware.

More information is available on Johnson-Davies' website, with Eagle design files and Gerber production files for the board available on GitHub under an unspecified open-hardware license.