Microcontroller ADC Resolution Boost Using an RC I/O Port
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Solution Overview
Problem
Current microcontrollers with 8-10 bit analog to digital (A/D) converters lack sufficient resolution for certain applications, and existing methods to increase resolution, such as over-sampling or using additional circuitry, are either costly or inefficient in capturing small signal changes.
Innovation Solution
A method utilizing a resistive-capacitive (RC) network connected to a microcontroller's input/output port to incrementally modify and measure a sense voltage, allowing for increased resolution by driving the port in output mode for controlled periods to achieve fractional resolution steps, thereby enhancing the effective resolution of A/D conversion without significant additional resources or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution A/D converter separate from the microcontroller is used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The microcontroller's I/O port is made multi-functional by allowing it to serve both as a digital output port for driving loads and as an analog input port for high-resolution voltage measurements. The port can be configured to operate in different modes (digital output, analog input, high-resolution measurement) depending on the application requirements, eliminating the need for separate dedicated high-resolution A/D converter circuits.
Solution Approach 2:
The microcontroller uses its own I/O port to perform high-resolution A/D conversion without requiring external high-resolution converter circuits. The system serves itself by utilizing the existing port infrastructure to achieve measurements with resolution exceeding the internal A/D converter capabilities, thereby reducing external component requirements and circuit complexity.
2Measurement precision
If over-sampling and averaging is used, then measurement precision is improved, but productivity decreases due to inability to capture small signal changes
Solution Approach 1:
The method changes the operating parameters of the I/O port by configuring it to operate in a special high-resolution measurement mode rather than standard digital or analog mode. By adjusting the port's operational parameters (enabling high-Z state, controlling drive time, setting appropriate voltage thresholds), the system achieves enhanced measurement resolution without requiring excessive sampling and averaging, thus maintaining faster conversion speeds.
3Measurement precision
If a voltage ramp comparator method is used, then measurement precision is improved, but device complexity and conversion time increase
Solution Approach 1:
The system performs preliminary configuration of the I/O port to the appropriate high-resolution measurement mode before actual measurements are taken. The port is pre-configured with the correct electrical characteristics (high-Z state, drive time constants, voltage thresholds) so that when measurements are performed, they can be completed quickly without requiring complex real-time ramp generation or extensive processing during the conversion itself.
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
This method effectively increases the resolution of A/D conversion by allowing precise measurement of small changes in voltage, improving the accuracy of digital representation without requiring additional circuitry or substantial resource usage, thus addressing the limitations of existing solutions.
Implementation Method 1
a resistive-capacitive (RC) network is connected between an input/output (I/O) port of the microcontroller and a sense voltage to be converted
Implementation Method 2
The port is then switched to output mode and driven high (or alternatively low) for a period of time, T1, to modify the sense voltage by an amount equal to a desired fractional resolution step size
Data Source
AI summary
A method for increasing the resolution of analog to digital conversion made by a microcontroller. A resistive-capacitive network is connected between an input/output port of the microcontroller and a sense voltage to be converted. The sense voltage is measured (i.e. converted) using the port in input mode to obtain a nominal voltage. The port is then switched to output mode and driven high (or alternatively low) for a period of time to modify the sense voltage by an amount equal to a desired fractional resolution step size. The port is switched back to input mode and the modified voltage is measured. The steps of driving the port in output mode and measuring the modified voltage can be repeated with the modification to the sense voltage increasing in successively larger multiples of the desired fractional resolution step size. In one embodiment of the method, the successive measurements can be summed to give the converted original sense voltage expressed in fractional resolution step size.