Single-Pin RC Identification Circuit for Multi-State Board ID
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Solution Overview
Problem
Conventional single-pin system level identification methods in embedded electronics require multiple pins or expensive analog-to-digital converter (ADC) circuits to provide more than two states, which is inefficient and costly.
Innovation Solution
A resistor/capacitor identification detection (RCID) interface that uses a single pin to identify multiple states by measuring discharge and charge times of an RC circuit, with a threshold detector and a 16-bit counter, allowing up to 20 quantized RC-constant states without the need for ADCs or external resistor dividers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ADC and external resistor divider circuits are used to provide more than two states on a single pin, then system level identification capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the identification function from complex ADC-based solutions and implements it using a simplified RC time constant measurement approach. By removing the ADC and resistor divider circuits, the solution achieves multi-state identification on a single pin with significantly reduced circuit complexity while maintaining the ability to distinguish multiple hardware configurations.
Solution Approach 2:
The patent replaces expensive ADC components with inexpensive RC circuit elements (resistors and capacitors) that can be easily implemented using simple lumped components. This substitution dramatically reduces cost while achieving the same functional goal of multi-state system identification.
2Adaptability or versatility
If multiple GPIO pins are used to provide 2N states of information, then system level identification capability is improved, but the number of pins required increases
Solution Approach 1:
The patent makes a single GPIO pin perform the function that would traditionally require multiple pins by using RC time constant measurement. The single pin is used for both charging and discharging the external RC circuit, and the measured time constants provide multi-state identification capability equivalent to or exceeding what multiple binary pins could achieve.
Solution Approach 2:
The patent transitions from a binary state space (two states per pin) to a continuous time domain measurement (RC time constants). By measuring the time dimension rather than using discrete voltage levels, the system achieves multi-state identification on a single pin, effectively adding a temporal dimension to the identification process.
3Ease of manufacture
If conventional pull-up/pull-down resistors are used on limited GPIO pins, then ease of manufacture is improved, but the number of available pins for identification is limited
Solution Approach 1:
The patent replaces the mechanical/physical constraint of having multiple discrete pins with an electrical measurement approach using RC time constants. Instead of physically adding more pins, the solution uses electrical measurement of charge/discharge times to achieve the same or greater identification capability, substituting a physical resource constraint with an electrical measurement solution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables low-cost, efficient identification of system element configurations using a single pin, reducing the number of pins required and eliminating the need for complex ADC-based solutions, while maintaining high accuracy and resolution.
Implementation Method 1
measuring the discharge and charge times for an RC circuit connected to a single I/O pin
Implementation Method 2
initiate the discharge, followed by the charging of the external RC circuit
Data Source
AI summary
A resistor/capacitor identification detection (RCID) circuit may provide system level identification of hardware (e.g. circuit board ID) through a single pin interface, by identifying up to a specified number of more than two quantized RC time constant states by measuring the discharge and charge times of an external RC circuit coupled to the single pin. The RCID circuit may initiate the discharge followed by a charging of the external RC circuit. The signal developed at the signal pin may be provided to the input of a threshold detector, with the threshold set at a specified percentage of a supply voltage used for operating the RCID circuit. The digitized output of the threshold detector may be used to gate a counter, after having been filtered through an input glitch rejection filter. A resolution of the counter may be determined by a high frequency clock used for clocking the counter. The numeric values of the charge and discharge times may be stored in data registers comprised in the RCID circuit.