In humanoid robotics, there is a long pursuit of making bipeds capable of walking in highly unstructured and roughly sensed environments. Within this goal, our objective is to develop a compliant bipedal humanoid robot, based on McKibben pneumatic actuators that can move in these terrains as well as quickly adapt to unpredicted variations on the contact state. We present here the first part of our work, focusing on the design, construction and control of a pneumatic robotic joint capable of achieving the control performance necessary for responding compliantly and accurately to contact transitions while delivering high forces needed to handle the physical challenges associated with rough terrains. In particular, we address our progress in the mechanical and embedded electronic design, actuator modeling, and compliant control strategies for a robotic joint based on fluidic pneumatic artificial muscles (PAMs). The proposed robotic joint has been validated experimentally, exploring various aspects of its performance as well as its shortcomings, but overall demonstrating the potential benefits of using pneumatic muscles. / text