Evaluation of analog and digital signal processing on PSoC architecture with DCT as use case: Comparison of an analog and software based implementation of the digital cosine transform on a Programmable System on Chip

One trend for signal processing hardware is the increasing integration of different functionalities in one mixed-signal chip. But the additional integration of analog components on one chip with digital components and a micro-processor like in the Programmable System on Chip (PSoC) from Cypress is accompanied with the extension of the design space and the need to explore it by evaluating different implementations with the same functionality to find a good trade-off between analog and digital signal processing. This paper evaluates different implementations of the discrete cosine transform (DCT) with different analog-digital partitioning. Therefore the DCT is integrated as software controlled analog circuit based on the switched capacitors and operational amplifiers available in the analog subsystem of the PSoC architecture. The presented analog DCT implementation scales linear and the number of simultaneously computable spectral signal components is only limited by the available on-chip resources on the currently used PSoC5LP. To evaluate the analog implementation, the DCT is also implemented as software executed on the ARM Cortex-M3 integrated in the PSoC5LP. The comparison of both solutions shows that the analog hardware available on the PSoC architecture can be used to directly process analog sensor signals with only minor additional off-chip components with a CPU load of about 8% caused by the software controlling the analog subsystem.