For embedded projects where power efficiency and hardware security matter more than raw compute, Conclusive Engineering has built the KSTR-SAMA5D27, a 7.0 x 5.0 cm (2.8 x 2.0 inches) single board computer around the Microchip SAMA5D27 system-in-package. The board pairs an Arm Cortex-A5 core running at 500 MHz with 256MB of LPDDR2 RAM, and draws less than 200 microamps in its low power state, dropping to just 5 microamps in backup mode. That makes it a compelling option for battery-powered IoT deployments and edge computing nodes that need to run Linux but not burn through power doing it.
What sets the KSTR-SAMA5D27 apart from the usual crop of small Linux boards is its expansion and peripheral mix. The two GPIO headers (34-pin and 30-pin) expose CAN Bus, a 6-channel ADC, 4-channel PWM, a 10-bit image sensor controller with 10-bit and 12-bit sensor support, PDMIC audio input, and two configurable Flexcom interfaces that can each operate as I2C, SPI, or UART. There is also a Qwiic connector for quick sensor hookups. Connectivity covers 10/100 Mbps Ethernet, WiFi 4, and Bluetooth 4.1, while a USB-C port handles both power and USB 2.0 OTG data. Li-Ion battery charging with temperature monitoring is built in, along with a coin cell backup for the onboard RTC and static RAM.
On the security side, the board leverages Arm TrustZone, Secure Boot, a hardware encryption engine, and a memory integrity monitor, features that are increasingly important for connected devices deployed in the field. The TrustZone hardware is complemented by OP-TEE, the open-source Trusted Execution Environment, which the board's AT91Bootstrap first-stage bootloader loads alongside U-Boot so that a trusted OS and Linux run concurrently, with dedicated Yocto and Buildroot images provided for that configuration. Storage comes via a microSD card slot and a small 4KB EEPROM for configuration data.
Software support covers Linux 6.1 and 6.5, U-Boot, the Yocto Project, Buildroot, and Ubuntu, with FreeBSD available on request. Source code for the board's Linux kernel fork (including the device tree), AT91Bootstrap, and U-Boot is maintained on Conclusive's public GitLab, giving developers a direct path to customization or contributing patches back to the broader AT91/SAMA5 ecosystem. Documentation and OS images are posted on the project wiki. The SAMA5D2 processor family dates back to 2018, but the KSTR-SAMA5D27 itself is a recent design. Samples are available from the Conclusive store for $119 (€109) plus VAT.
