  The Gamma-ray Module (GMOD) is an experiment designed for the detection of
gamma-ray bursts in low Earth orbit as the principal scientific payload on a
2-U CubeSat, EIRSAT-1. GMOD comprises a cerium bromide scintillator coupled to
silicon photomultipliers which are processed and digitised by a bespoke ASIC.
Custom firmware on the GMOD motherboard has been designed, implemented and
tested for the MSP430 microprocessor which manages the experiment including
readout, storage and configuration of the system. The firmware has been
verified in a series of experiments testing the response over a realistic range
of input detector trigger frequencies from 50Hz to 1kHz for the primary time
tagged event (TTE) data. The power consumption and ability of the firmware to
successfully receive and transmit the packets to the on-board computer was
investigated. The experiment demonstrated less than 1% loss of packets up to
1kHz for the standard transfer mode with the power not exceeding 31mW. The
transfer performance and power consumption demonstrated are within the required
range of this CubeSat instrument.
