  This paper addresses the stability and $\ell^2$-gain analysis of adaptive
control systems with event-triggered try-once-discard protocols. At every
sampling time, an event trigger evaluates an error between the current value
and the last released value of each measurement and determines whether to
transmit the measurements and which measurements to transmit, based on the
try-once-discard protocol and given lower and upper thresholds. For
gain-scheduling controllers and switching controllers that are adaptive to the
maximum error of the measurements, we obtain sufficient conditions for the
practical stability and upper bounds on the $\ell^2$-gain of the closed-loop
system.
