The sensor and actuator interface is an essential part of the project. It is concerned with the communication between the manipulator and the workstation used to control it. The problem required interfacing a SUN workstation with 3 Motors, each of which drives a link of the 3 link robot arm. A resident program on the SUN can send out voltage values that will drive the motors in a desired direction (forward or backward), and read values from sensors placed on the motors that correspond to the position of the motors. So thinking at a higher level, it was obvious that we would need A/Ds to convert the values coming from the motors to digital so that they can be sent to the workstation (where the control program resides ), D/As to convert the values sent by the program to the actual analog voltage and an RS-232 communication to the workstation to send these digital data to and from the workstation. Also we would need some control of sampling, sending and receiving data outside the workstation.
So based on the suggestion of Digital Systems Laboratory (DSL), we decided to go for a Microcontroller which can control the A/D conversion , D/A conversion and the RS-232 communication protocol with the workstation. The one that came in handy was the MC68HC11EVBU - Universal Evaluation Board, which has a microcontroller, an 8-channel A/D, an RS-232 compatible terminal I/O port, and some wire wrap area for additional circuitry like the D/A unit.