Embedded systems have more usability dimension as compared to general-purpose computers. Hence, the need to have more diverse and effective ways to evaluate such systems is imperative. This paper proposes the use of rubrics in the evaluation of usability on embedded systems. The result is a generalized rubric for usability testing intended for evaluation on embedded systems. The rubric is evaluated by certified testers through a validation experiment on a mobile robot. The majority of the experts felt that the rubric was complete, likely to be effective in providing good testing results, usable by embedded system testers, and appealing for them to consider it themselves.