Firmware headroom and USB connectivity
The MSP430F5502IRGZT packs a 25MHz MSP430 CPUXV2 core with 24KB of flash and 6KB of RAM — enough for a USB-stack-based control loop without starving the application heap. The on-chip USB 2.0 PHY (full-speed) plus I2C, SPI, and UART means this single 16-bit MCU handles both the host link and sensor/peripheral buses on one die.
The 31 GPIOs break out to the perimeter — the pad is the only power/ground connection on the bottom, so the layout must allocate at least four vias per amp of core current.