Superconducting Transition Edge sensors (TESs) are energy-resolving thermal sensors that are enabling a broad spectrum of science due to their innate characteristics; excellent energy resolution combined with high efficiency. Emerging systems based on TESs are expected to contain many thousands of sensors and/or sensors with time constants as short as 100 us. These requirements must be satisfied while maintaining low noise and low crosstalk. A promising readout solution for large TES arrays is the microwave SQUID multiplexer, which offers several gigahertz of readout bandwidth per pair of coaxial cables. Microwave SQUID multiplexing moves complexity from the cryogenic stages to room temperature hardware and digital signal processing firmware, which must synthesize the microwave tones and process the information contained within them.

To demultiplex at room-temperature, we have implemented an FPGA-based solution using the ROACH2 hardware platform developed by the CASPER consortium. We have successfully developed a flexible firmware architecture that, with few modifications, can read out implementations of microwave SQUID multiplexers optimized for bolometric, high count rate x-ray, and AC-bias TES applications. This talk will briefly describe transition-edge sensors and the SQUID microwave multiplexer, before describing the microwave multiplexing firmware in detail.