Olimex Respins ESP32-S2-DevKit-Lipo to Unlock the ESP32-S2's On-Board USB OTG Functionality
Redesign may be the first ESP32-S2 development board to offer USB OTG support — though the software side's still pending.
Bulgarian open source specialist Olimex has announced a respin of its ESP32-S2-DevKit-Lipo board, announced just over a week ago, to unlock the USB On The Go (OTG) functionality of the Espressif ESP32-S2 microcontroller.
Olimex unveiled the ESP32-S2-based development board, built for low power draw in battery-based projects, just over a week ago. In addition to the ESP32-S2 at its heart, the board also came equipped with a CH340T USB-TTL serial adapter. "Many have noticed that ESP32-S2 has a native USB-OTG," Olimex writes. "Then why did we put the CH340T on it? The reason is that the Espressif SDK didn’t support USB back when we designed this board."
"Now Espressif SDK adds support for a USB bootloader and the programming of the ESP32-S2 can be done by the native USB interface, we decided to make a new revision where the native USB-OTG interface is used."
Switching to the on-board USB OTG interface wasn't quite as simple as it sounds, however. "We wanted to keep the LiPo battery functionality and this created an interesting technical challenge: The USB-OTG port can be used both as device and host," the company explains. "When used as a device, the board is powered by the USB and LiPo battery is charging.
"When used as a USB host (i.e. you can attach USB devices to the port) the USB port must supply 5V to the USB devices connected. Our first prototype had a power supply problem: when the ESP32-S2 works as a host the battery is powering the USB-OTG port with 5V, but there is attached also the LiPo charger circuit, so infinite loop is made: battery -> step up to 5V -> USB -> LiPo charger -> battery. This issue was preventing us from releasing this board earlier, but now on Rev.B all of these issues are fixed so we are about to run production."
The revised model — the first ESP32-S2-based board to offer USB OTG functionality, the company claims — retains the low 30µA deep-sleep specification as its predecessor, and will be released under an open licene as before. "To the best of our knowledge there is still no software support for a USB host on the ESP32-S2," Olimex admits, "but we hope after our hardware is released this will push and accelerate the software development further."
Stock of the new boards is expected in the coming weeks, with more information available on the company's website.