Microcontroller FSK Modem Software Implementation
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Solution Overview
Problem
Existing FSK modems in PLC systems require additional hardware, such as UARTs, and suffer from poor signal quality and increased cost due to the need for isolation barriers and multiple modems in multi-channel designs, limiting their efficiency and space usage.
Innovation Solution
Implementing a software-implemented FSK modem function within a micro-controller, which eliminates the need for separate hardware modems and reduces communication lines across isolation barriers, using an analog-to-digital converter to demodulate FSK signals and improve signal fidelity through adaptive center point adjustment and zero crossing detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If off-the-shelf HART modems are used in PLC systems, then FSK communication functionality is achieved, but additional hardware (UART, isolation barriers) is required increasing device complexity and cost
Solution Approach 1:
The patent merges the FSK modem functionality directly into the microcontroller unit (MCU) by implementing a software-based FSK modem that uses the MCU's built-in ADC and timer resources. This eliminates the need for separate hardware modems and UART peripherals, integrating multiple functions into a single device component.
Solution Approach 2:
The patent replaces hardware-based FSK modulation/demodulation with a software-implemented solution running on the MCU. The software modem uses the MCU's ADC to capture analog signals and processes FSK demodulation algorithmically, substituting physical hardware components with computational logic.
2Productivity
If multiple FSK modems are implemented for multi-channel designs, then channel capacity increases, but cost and space consumption increase due to isolation barriers and separate modem hardware
Solution Approach 1:
The patent creates a universal FSK modem implementation that can serve multiple communication channels simultaneously through software configuration. A single MCU can handle multiple FSK channels by time-division multiplexing or parallel processing of multiple ADC inputs, eliminating the need for dedicated hardware modems per channel.
Solution Approach 2:
The patent segments the FSK communication functionality into software modules that can be independently configured for different channels. Each channel's FSK processing is handled by separate software task or interrupt handler, allowing logical separation of multiple channels without requiring physical hardware separation.
3Device complexity
If software-implemented FSK modem is used, then hardware requirements are reduced, but signal processing accuracy may be compromised
Solution Approach 1:
The patent implements feedback mechanisms in the software FSK modem including adaptive threshold adjustment based on signal strength detection and calibration routines that measure actual signal characteristics and adjust processing parameters accordingly. This feedback loop maintains high signal processing accuracy despite the software-based implementation.
Solution Approach 2:
The patent employs parameter optimization techniques where the software modem dynamically adjusts processing parameters such as ADC sampling rate, filter coefficients, and decision thresholds based on the specific signal conditions. This adaptive parameter tuning ensures high signal processing accuracy across varying operational conditions.
Data Source
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AI summary
A micro-controller to perform the FSK (HART) modem functions as well as communications and control functions in an isolated channel implementation is described. In one embodiment, the micro-controller comprises: a processor, an analog-to- digital converter configured to transform received analog signals into digital values at a predetermined digital sample rate; and a memory unit containing a set of computer- executable instructions that, when executed on the processor, provide a built-in FSK bi-directional modem function that converts the received digital values into binary signals. The FSK (HART) demodulation function is performed by the micro-controller with the built-in FSK modem function in three sequential phases implemented in computer code: (1) zero crossing and amplitude detection; (2) bit stream and timing generation, and (3) character generation and bit synchronization.