This interface is a pressure variable-resistive fabric (eeonyx type) implemented with row-scanning and virtual ground op-amp technique (see paper below).
This project implements a number of interesting features of micro-OSC:
- High speed reporting mode
- Sequence numbers (to infer the state of the multiplex driver)
- Low impedance input mode of analog input
- Ratiometric analog inputs using the virtual ground of the op-amp as Vref+.
- Simultaneous direction and pin state mux switching
There are a number of observed problems with this prototype:
- Glue on conductive tape is not reliable, results in disconnects to the wire attachment
- Considerable hysteresis is observed in the fabric; could be the fault of the glue. Perhaps the stitching method is better.
- The op-amp circuit is suboptimal since I used a shottky diode construction instead of an actual negative power supply.
- Through-hole parts and protoboard construction is extremely tedious in this volume of connections.
A tactile sensor sheet using pressure conductive rubber with electrical-wires stitched method, Shimojo, M. Namiki, A. Ishikawa, M. Makino, R. Mabuchi, K., Sensors Journal, IEEE, Oct. 2004