This letter presents closed-loop position control of a pneumatically actuated modular robotic platform "pneumagami" that can be stacked to enlarge work and design space for wearable applications. The module is a 3 degrees of freedom (DoF) parallel robot with two rotational and one translational motion, which is actuated by three antagonistic pneumatic pouch motor pairs attached to three leg joints. To control the pouch motors, we utilize miniature proportional valves. As for the sensing, we introduce a novel embedded resistive sensor mechanism utilizing rotary-to-translational transmission. The sensor's transmission is modeled and verified by experiments. Furthermore, we study analytic forward and inverse kinematic models of the pneumagami module. Utilizing the models, we design a closed-loop feedback controller to track two different trajectories. The experimental results show that the module follows the desired trajectories successfully. Thus, we report that the proposed pneumagami modules can be utilized for achieving a controllable robotic third arm with higher DoFs and range of motion (RoM) when connected in series.