Design and implementation of an all-digital scanned probe microscope controller.

摘要

Hardware for the data conversion required by a Scanned Probe Microscope controller is designed and built. This hardware is used to implement a DSP-based generic digital controller. The generality of the system is kept whenever possible to allow for compatibility with a wide range of SPMs.;The controller is built around a Motorola 56001 Digital Signal Processor. This processor is then interfaced to 486DX2-66 IBM compatible Personal Computer, through an ISA bus prototype card. The custom built hardware includes a printed circuit board that implements all data conversion to and from the analogue and digital domains. The I/O board incorporates optically isolated 20-bit digital-to-analogue converters and 18-bit analogue-to-digital converters. Six, input and output channels with three outputs amplified to implement the control signals of a PZT positioner are implemented in the I/O board. The I/O board usefulness and generality is maintained by using an FPGA to program the interface to the Digital Signal Processor.;Software to implement a Proportional Integral (PI) controller on the DSP is written. The controller's generality is kept by allowing one or two images to be obtained at the same time. The software running on the DSP generates all control signals to control a single closed loop plus a positioner, such as the case of the raster signal for a PZT. The DSP software also handles coarse approach to the sample through a stepper motor.