  Photon counting detector systems on sounding rocket payloads often require
interfacing asynchronous outputs with a synchronously clocked telemetry (TM)
stream. Though this can be handled with an on-board computer, there are several
low cost alternatives including custom hardware, microcontrollers and
field-programmable gate arrays (FPGAs). This paper outlines how a TM interface
(TMIF) for detectors on a sounding rocket with asynchronous parallel digital
output can be implemented using low cost FPGAs and minimal custom hardware. Low
power consumption and high speed FPGAs are available as commercial
off-the-shelf (COTS) products and can be used to develop the main component of
the TMIF. Then, only a small amount of additional hardware is required for
signal buffering and level translating. This paper also discusses how this
system can be tested with a simulated TM chain in the small laboratory setting
using FPGAs and COTS specialized data acquisition products.
