Logic Analyzer

Read more about the article Working with Logic Analyzer in PSLab Android app

Working with Logic Analyzer in PSLab Android app

This blog demonstrates the working of Logic Analyzer instrument available in PSLab Android app. It also includes a detailed description of the features available in the Logic Analyzer instrument along with a step by step guide on how to work with it which will be beneficial to first-time users of the PSLab application. The functionality of the Logic Analyzer available in PSLab Android app is same as that in PSLab Desktop App. So, it would be easy for a user of PSLab Desktop Application to get acquainted with this Logic Analyzer. The only difference in this instrument is the changed and attractive UI which makes working with it very easy. Why use Logic Analyzer? The Logic Analyzer instrument provides the functionality of capturing and plotting the digital waves on the screen so that it would be easy for a user to determine the time relationship between different waves. So, this instrument would be very useful while working with timing diagrams, protocol decodes, state machines traces, assembly language, or with source-level software. How to generate different digital pulses in the PSLab app? Logic Analyzer needs to be provided with some input of digital pulses among whom time relationship is to be found out. Digital pulses generated from different systems can be directly provided as input to the Logic Analyzer for analyzing. But PSLab provides a functionality to generate digital pulses up to some constrained frequency. Following are the steps to generate different digital waves in PSLab Android application : Open PSLab Android application and click on the Wave Generator tile as shown in figure 1. After opening the instrument, the screen will look as shown in figure 2. Figure 1. Wave Generator instrument tile available in PSLab Android app Figure 2. The main screen of the Wave Generator instrument Click on the MODE button to change the mode to PWM. The screen will look as shown in figure 3. Figure 3. PWM mode in Wave Generator PSLab device provides generation of maximum four digital waves at once. In this example, I will proceed by utilizing only two pins i.e. SQR1and SQR2 (where SQR = Acronym of square wave generator and the number next to it is the pin ID available on the PSLab device) to demonstrate the working of Two Channel Mode in Logic Analyzer. Set the duty cycles and frequency for the selected pins as desired (try to keep all the duty cycles different from each other to understand the process of measurement easily). NOTE: User can also set phase angle for different waves but I will proceed with defaults. How to analyze the generated waves in Logic Analyzer? Now go back and select the Logic Analyzer tile as shown in figure 4 from the list of available instruments. A screen as shown in figure 5 should open. Figure 4. Tile of Logic Analyzer instrument available in the PSLab app Figure 5. The main screen of the Logic Analyzer instrument On the right-hand side, you can see a slider whose…

Continue ReadingWorking with Logic Analyzer in PSLab Android app
Read more about the article Working with Logic Analyzer in PSLab application

Working with Logic Analyzer in PSLab application

This blog demonstrates the working of Logic Analyzer instrument available in PSLab Desktop Application. It also includes a detailed description of the features available in the Logic Analyzer instrument. Also, it provides a step by step guide on how to work with the Logic Analyzer provided by PSLab which will be beneficial to first-time users. What is a Logic Analyzer? A Logic Analyzer is an electronic instrument used to capture and display digital signals with an added functionality of providing the time difference between different edges of different pulses. It is mainly used to observe the time relationship between different digital signals. An example of a standard Logic Analyzer available in the market is as shown in figure 1. Figure 1. Standard Logic Analyzer How to generate different digital pulses in PSLab? Logic Analyzer needs to be provided with some input of digital pulses among whom time relationship is to be found out. Digital pulses generated from different systems can be directly provided as input to the logic analyzer for analyzing. But PSLab provides a functionality to generate digital pulses up to some constrained frequency. Following are the steps to generate different digital waves in the PSLab desktop application : Go to Advanced Control Section of PSLab app. The screen should look like one as shown in Figure 2. Figure 2.  Advanced Control Section PSLab device provides generation of maximum four digital waves at once. In this example, I will proceed by utilizing all the four pins i.e. SQR1, SQR2, SQR3, SQR4 (where SQR = Acronym of square wave generator and the number next to it is the pin ID available on the PSLab device). Set the duty cycles for each of the pins as desired (try to keep all the duty cycles different from each other to understand the process of measurement easily). After setting it should look something like Figure 3. Figure 3. Configuring PWM NOTE: User can also set phase angle for different waves but I will proceed keeping all without any phase difference. Now set the frequency of the digital waves in the tab provided next to text Frequency and then press the SET button. This should generate desired digital waves when connected. How to analyze the generated waves in Logic Analyzer? Now go to the Experiments section and click on the Logic Analyzer instrument as shown in Figure 4. Figure 4. Test and Measurement Page Now a screen as shown in Figure 5 should open which is the main screen for Logic Analyzer Instrument. Figure 5. Logic Analyzer Main Page On the right, you can see three buttons i.e Start, Plot Data and Raw Data. Below that selection for the number of channels is provided. And at last, the time measurement tool is provided which can measure the time difference between different edges of different digital waves. The graph at the center is the place where all the waves generated will be plotted. Now as we have generated four different waves, we need to navigate to…

Continue ReadingWorking with Logic Analyzer in PSLab application
Read more about the article Plotting Digital Logic Lines In PSLab Android App

Plotting Digital Logic Lines In PSLab Android App

The PSLab device offers the Logic Analyzer functionality. A Logic Analyzer is a laboratory instrument that can capture and display digital signals from a digital system or circuit. It is similar to what an oscilloscope is for analog signals and is used to study timing relationship between different logic lines. It plots the logic lines/timing diagram which tells us the information about the state of the Digital System at any instant of time. For example, in the image below we can study the states of digital signals from channels ID1, ID2, ID3 at different times and find parameters like the propagation delay. It's also used to find errors in Integrated Circuits (ICs) and debug logic circuits. How I plotted ideal logic lines using MPAndroid Chart library? Conventional method of adding data points results in the plot as illustrated in the image below. By conventional method I mean basically adding Y-axis (logic state) values corresponding to X-axis values (timestamp). In the above plot, logic lines follow non-ideal behaviour i.e they take some time in changing their state from high to low. This non-ideal behaviour of these lines increases when the user zooms in graph to analyse timestamps. Solution to how we can achieve ideal behaviour of logic lines: A better solution is to make use of timestamps for generating logic lines i.e time instants at which logic made a transition from HIGH -> LOW or LOW -> HIGH. Lets try to figure out with an example: Timestamps = { 1, 3, 5, 8, 12 } and initial state is HIGH ( i.e at t = 0, it's HIGH ). This implies that at t = 1, transition from HIGH to LOW took place so at t = 0, it's HIGH, t = 1 it's both HIGH and LOW,  at t = 2 it's LOW. Now at t = 0 & t = 2, you can simple put y = 1 and 0 respectively. But how do you add data-point for t = 1. Trick is to see how transition is taking place, if it's HIGH to LOW then add first 1 for t = 1 and then 0 for t = 1. So the set of points look something like this: ( Y, X ) ( LOGIC , TIME ) -> ( 1, 0 ) ( 1, 1 ) ( 0, 1) ( 0, 2 ) ( 0, 3 ) ( 1, 3 )  ( 1, 4 ) … Code snippet for adding coordinates in this fashion: int[] time = timeStamps.get(j); for (int i = 0; i < time.length; i++) {   if (initialState) {       // Transition from HIGH -> LOW       tempInput.add(new Entry(time[i], 1));       tempInput.add(new Entry(time[i], 0));   } else {       // Transition from LOW -> HIGH       tempInput.add(new Entry(time[i], 0));       tempInput.add(new Entry(time[i], 1));   }   // changing state variable   initialState = !initialState; } After adding data-points in above mentioned way, we obtained ideal logic lines successfully as illustrated in the image given below Resources Documentation of MPAndroid Chart library Sparkfun tutorials to learn more about…

Continue ReadingPlotting Digital Logic Lines In PSLab Android App
Read more about the article Environment Monitoring with PSLab

Environment Monitoring with PSLab

In this post, we shall explore the working principle and output signals of particulate matter sensors, and explore how the PSLab can be used as a data acquisition device for these. Working Principle A commonly used technique employed by particulate matter sensors is to study the diffraction of light by dust particles, and estimate the concentration based on a parameter termed the ‘occupancy factor’. The following image illustrates how the most elementary particle sensors work using a photogate, and a small heating element to ensure continuous air flow by convection. Occupancy Rate Each time a dust particle of aerodynamic diameters 2.5um passes through the lit area, a phenomenon called Mie scattering which defines scattering of an electromagnetic plane wave by a homogenous sphere of diameter comparable to the wavelength of incident light, results in a photo-signal to be detected by the photosensor.  In more accurate dust sensors, a single wavelength source with a high quality factor such as a laser is used instead of LEDs which typically have broader spectra. The signal output from the photosensor is in the form of intermittent digital pulses whenever a particle is detected. The occupancy ratio can be determined by measuring the sum total of time when a positive signal was output from the sensor to the total averaging time. The readings can be taken over a fairly long amount of time such as 30 seconds in order to get a more accurate representation of the occupancy ratio. Using the Logic analyzer to capture and interpret signals The PSLab has a built-in logic analyzer that can acquire data signals up to 67 seconds long at its highest sampling rate, and this period is more than sufficient to record and interpret a dataset from a dust sensor. An inexpensive dust sensor, DSM501A was chosen for the readings, and the following results were obtained Dust sensor readings from an indoor, climate controlled environment. After the 100 second mark, the windows were opened to expose the sensor to the outdoor environment. A short averaging time has resulted in large fluctuations in the readings, and therefore it is important to maintain longer averaging times for stable measurements. Recording data with a python script instead of the app The output of the dust sensor must be connected to ID1 of the PSLab, and both devices must share a common ground which is a prerequisite for exchange of DC signals. All that is required is to start the logic analyzer in single channel mode, wait for a specified averging time, and interpret the acquired data Record_dust_sensor.py from PSL import sciencelab #import the required library import time import numpy as np I = sciencelab.connect() #Create the instance I.start_one_channel_LA(channel='ID1',channel_mode=1,trigger_mode=0) #record all level changes time.sleep(30) #Wait for 30 seconds while the PSLab gathers data from the dust sensor a,_,_,_,e =I.get_LA_initial_states() #read the status of the logic analyzer raw_data =I.fetch_long_data_from_LA(a,1) #fetch number of samples available in chan #1 I.dchans[0].load_data(e,raw_data) stamps =I.dchans[0].timestamps #Obtain a copy of the timestamps if len(stamps)>2: #If more than two timestamps are…

Continue ReadingEnvironment Monitoring with PSLab