NXP MPX4100A Sensor Calibration Use Case

Example demonstrating output uncertainty estimation for calibrated ADC values from the MPX4100A sensor¹.

Introduction

The MPX4100A is a 20 to 250 kPa range integrated pressure sensor.

Getting started

The correct way to clone this repository to get the submodules is:

	git clone --recursive git@github.com:signaloid/Signaloid-Demo-Sensors-NXPMPX4100AConversionRoutines.git

If you forgot to clone with --recursive and end up with empty submodule directories, you can remedy this with:

	git submodule update --init

Running the application locally

Apart from using Signaloid's Cloud Compute Platform, you can compile and run this application locally. Local execution is essentially a native Monte Carlo implementation, that uses GNU Scientific Library (GSL)² to generate samples for the different input distributions. In this mode the application stores the generated output samples, in a file called data.out. The first line of data.out contains the execution time of the Monte Carlo implementation in microseconds (μs), and each next line contains a floating-point value corresponding to an output sample value. Please note, that for the Monte Carlo output mode, you need to select a single output to calculate, using (-S) command-line option.

In order to compile and run this application in the native Monte Carlo mode:

0. Install dependencies (e.g., on Linux):

sudo apt-get install libgsl-dev libgslcblas0

1. Compile natively (e.g., on Linux):

cd src/
gcc -I. -I/opt/local/include main.c utilities.c common.c uxhw.c -L/opt/local/lib -o native-exe -lgsl -lgslcblas -lm

2. Run the application in the MonteCarlo mode, using (-M) command-line option:

./native-exe -M 10000

The above program runs 10000 Monte Carlo iterations.

3. See the output samples generated by the local Monte Carlo execution:

cat data.out

Inputs

The inputs to the NXPMPX4100A sensor conversion algorithms are the raw ADC taken from the voltage output of the sensor ($V_{out}$) as well as the supply voltage of the sensor ($V_{s}$). The algorithm models the ADC quantization error as well as the uncertainty in the supply voltage using uniform distributions.

The uncertainty in $V_{out}$ is modeled as a (UniformDist(2.3, 2.7)) Volts.

The uncertainty in $V_{s}$ is modeled as a (UniformDist(4.8, 5.4)) Volts.

Outputs

The output of the application is the calibrated pressure, calculated by:

$$\mathrm{Calibrated Sensor Output} = \frac{(V_{out}/V_{s} + 0.1518)}{0.01059}$$

Following is an example output, using Signaloid's C0Pro-S core:

Usage

Example: NXPMPX4100A sensor conversion routines - Signaloid version

Usage: Valid command-line arguments are:
        [-o, --output <Path to output CSV file : str>] (Specify the output file.)
        [-S, --select-output <output : int>] (Compute 0-indexed output, by default 0.)
        [-M, --multiple-executions <Number of executions : int (Default: 1)>] (Repeated execute kernel for benchmarking.)
        [-T, --time] (Timing mode: Times and prints the timing of the kernel execution.)
        [-b, --benchmarking] (Benchmarking mode: Generate outputs in format for benchmarking.)
        [-j, --json] (Print output in JSON format.)
        [-h, --help] (Display this help message.)

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Footnotes

1. NXP MPX4100A, 20 to 250 kPa, Absolute, Integrated Pressure Sensor Datasheet. ↩

2. GNU Scientific Library ↩