EV-HT-200CDAQ1 builds on the CN0365 analog front end reference design from with the goal of providing a foundation for a high temperature, low power microcontroller-based data acquisition and control solution that meets the requirements for many downhole instrumentation and other high temperature applications. Based upon the AD7981 analog-to-digital SAR converter, this reference design demonstrates a full featured system with two high speed simultaneously sampled channels along with 8 additional multiplexed channels suitable for covering the acquisition requirements of a broad range of downhole tools (10 channels total). This analog front end is connected to the VORAGO Technologies VA10800 ARM® Cortex^®-M0 based microcontroller via multiple SPI ports. Once acquired, the data can be processed locally or transmitted via a UART or optional RS485 communications interface. Other supporting components on the board, including memory, clock, power and passives are all rated for high temperature operation by their respective suppliers and verified to operate reliably at 200°C or higher. In addition to the hardware, open source firmware is supplied for the project using FreeRTOS with optimized drivers and data acqusition protocol with multiple modes of operation. Open source PC software included allows the users to connect to the board via UART to control acquisition modes, view data, log data and perform signal analysis. This platform is suitable for reference design, rapid prototyping (such as new sensor techniques) and lab testing of high temperature instrumentation systems.