BeagleConnect Zepto: A $1 Smart ADC for Linux

BeagleConnect Zepto puts a low-cost microcontroller between sensors and a Linux system, using it as what BeagleBoard.org founder Jason Kridner calls a “smart ADC.” In this Elektor TV clip from Practical IoT Sensor Systems with BeagleBoard and TI, Kridner explains how one small MCU can add analog conversion, UARTs, and other I/O while handling timing-sensitive work locally before Linux needs to see it.

BeagleConnect Zepto as a Smart ADC

At the center of the board is Texas Instruments’ MSPM0L1117, an Arm Cortex-M0+ MCU running at up to 32 MHz with 128 KB of flash and 16 KB of SRAM. BeagleBoard.org’s official introduction describes a minimal two-layer design intended to reach a roughly $1 development-board price point. Kridner’s point is both economic and architectural: a very low-cost MCU can sometimes cost less than a dedicated ADC while also providing timers, interrupts, GPIO, serial interfaces, and enough processing to do useful work on the samples.

For a Linux host, that local processing can be more useful than simply adding another converter. The MCU can respond to low-latency interrupts, sample data continuously, apply first-pass filtering, and pass on only the data or events the higher-level system needs. Linux can then handle networking, storage, user interfaces, and application logic without being expected to react to every sensor transition.

More I/O Without More Firmware

The board also provides friction-fit mikroBUS-compatible through-holes and Qwiic connectivity, giving it access to a broad range of sensor and actuator modules. The software side is built around Zephyr and BeagleConnect Greybus, with the aim of exposing attached peripherals to a Linux host without writing a one-off microcontroller application for every module. The current Zephyr board documentation lists support for the MSPM0L1117 platform and peripherals including its ADC, GPIO, UART, SPI, and timers.

A Low-Cost Zephyr Development Board

BeagleConnect Zepto has a second job in Kridner’s explanation: it is intended to be a very inexpensive open development platform for Zephyr. In the clip he notes that the board is not yet readily available at retail, although hundreds have already been distributed to developers. The low price target suits teaching, experiments, and designs that need several sensor nodes rather than one relatively expensive controller.

The “smart ADC” approach does not make a dedicated converter obsolete. Precision, noise, bandwidth, linearity, channel isolation, or specialized front-end requirements can still call for a purpose-built ADC. For many embedded sensor systems, however, a low-cost microcontroller can combine conversion, timing, filtering, communications, and control in one part, giving designers another option before automatically adding a separate IC.