Pocket Science

Read more about the article Expandable ListView In PSLab Android App

Expandable ListView In PSLab Android App

In the PSLab Android App, we show a list of experiments for the user to perform or refer to while performing an experiment, using PSLab hardware device. A long list of experiments need to be subdivided into topics like Electronics, Electrical, School Level, Physics, etc. In turn, each category like Electronics, Electrical, etc can have a sub-list of experiments like: Electronics Diode I-V characteristics Zener I-V characteristics Transistor related experiments Electrical Transients RLC Bode Plots Ohm's Law This list can continue in similar fashion for other categories as well. We had to  display  this experiment list to the users with a good UX, and ExpandableListView seemed the most appropriate option. ExpandableListView is a two-level listView. In the Group view an individual item can be expanded to show it's children. The Items associated with ExpandableListView come from ExpandableListAdapter.                 Implementation of Experiments List Using ExpandableListView First, the ExpandableListView was declared in the xml layout file inside some container like LinearLayout/RelativeLayout. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"   android:layout_width="match_parent"   android:layout_height="match_parent"   android:orientation="vertical">   <ExpandableListView       android:id="@+id/saved_experiments_elv"       android:layout_width="match_parent"       android:layout_height="wrap_content"       android:divider="@color/colorPrimaryDark"       android:dividerHeight="2dp" /> </LinearLayout> Then we populated the data onto the ExpandableListView, by making an adapter for ExpandableListView by extending BaseExpandableListAdapter and implementing its methods. We then passed a Context, List<String> and Map<String,List<String>> to the Adapter constructor. Context: for inflating the layout List<String>: contains titles of unexpanded list Map<String,List<String>>: contains sub-list mapped with title string public SavedExperimentAdapter(Context context,                                 List<String> experimentGroupHeader,                                 HashMap<String, List<String>> experimentList) {       this.context = context;       this.experimentHeader = experimentGroupHeader;       this.experimentList = experimentList;   } In getGroupView() method, we inflate, set title and return group view i.e the main list that we see on clicking and the  sub-list is expanded. You can define your own layout in xml and inflate it. For PSLab Android, we used the default one provided by Android android.R.layout.simple_expandable_list_item_2 @Override public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {   String headerTitle = (String) getGroup(groupPosition);   if (convertView == null) {       LayoutInflater inflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);       convertView = inflater.inflate(android.R.layout.simple_expandable_list_item_2, null);   }   TextView tvExperimentListHeader = (TextView) convertView.findViewById(android.R.id.text1);   tvExperimentListHeader.setTypeface(null, Typeface.BOLD);   tvExperimentListHeader.setText(headerTitle);   TextView tvTemp = (TextView) convertView.findViewById(android.R.id.text2);   tvTemp.setText(experimentDescription.get(groupPosition));   return convertView; } Similarly, in getChildView() method, we inflate, set data and return child view. We wanted simple TextView as sub-list item thus inflated the layout containing only TextView and setText by taking reference of textView from the inflated view. @Override public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {   String experimentName = (String) getChild(groupPosition, childPosition);   if (convertView == null) {       LayoutInflater inflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);       convertView = inflater.inflate(R.layout.experiment_list_item, null);   }   TextView tvExperimentTitle = (TextView) convertView.findViewById(R.id.exp_list_item);   tvExperimentTitle.setText(experimentName);   return convertView; } The complete code for the Adapter can be seen here. After creating the adapter we proceeded similarly to the normal ListView. Take the reference for ExpandableListView by findViewById() or BindView if you are using ButterKnife and set the adapter as an instance of adapter created above. @BindView(R.id.saved_experiments_elv) ExpandableListView experimentExpandableList; experimentAdapter = new SavedExperimentAdapter(context, headerList, map); experimentExpandableList.setAdapter(experimentAdapter); Roadmap We are planning to divide the experiment sub-list into categories like Electronics Diode Diode I-V Zener…

Continue ReadingExpandable ListView In PSLab Android App
Read more about the article Communication by pySerial python module in PSLab

Communication by pySerial python module in PSLab

In the PSLab Desktop App we use Python for communication between the PC and PSLab device. The PSLab device is connected to PC via USB cable. The power for the hardware device is provided by the host through USB which in this case is a PC. We need well structured methods to establish communication between PC and PSLab device and this is where pySerial module comes in. We will discuss how to communicate efficiently from PC to a device like PSLab itself using pySerial module. How to read and write data back to PSLab device? pySerial is a python module which is used to communicate serially with microcontroller devices like Arduino, RaspBerry Pi, PSLab (Pocket Science Lab), etc. Serial data transfer is easier using this module, you just need to open a port and obtain serial object, which provides useful and powerful functionality. Users can send string (which is an array of bytes) or any other data type all data types can be expressed as byte string using struct module in python, read a specific number of bytes or read till some specific character like ‘\n’ is encountered. We are using this module to create custom read and write functions. How to Install pySerial and obtain serial object for communication? You can install pySerial using pip by following command pip install pyserial Once it's installed we can now import it in our python script for use. Obtain Serial Object In Linux >>> import serial >>> ser = serial.Serial('/dev/ttyUSB0') In Windows >>> ser = serial.Serial() >>> ser.baudrate = 19200 >>> ser.port = 'COM1' Or >>> ser = serial.Serial('COM1', 19200) You can specify other properties like timeout, stopbits, etc to Serial constructor. Complete list of parameters is available here. Now this “ser” is an object of Serial class that provides all the functionalities through its interface. In PSLab we obtain a serial object and implement custom methods to handle communication which isn’t directly provided by pySerial, for example if we need to implement a function to get the version of the PSLab device connected. Inside the version read function we need to send some bytes to the device in order to obtain the version string from device as a byte response. What goes under the hood? We send some sequence of bytes to PSLab device, every sequence of bytes corresponds to a unique function which is already written in device’s firmware. Device recognises the function and responses accordingly. Let's look at code to understand it better. ser.write(struct.Struct('B').pack(11))  #  Sends 11 as byte string ser.write(struct.Struct('B').pack(5))   #  Sends 5 as bytes string x = ser.readline()                      #  Reads bytes until ‘\n’ is encountered    To understand packing and unpacking using struct module, you can have a read at my other blog post Packing And Unpacking Data in JAVA in which I discussed packing and unpacking of data as byte strings and touched a bit on How it's done in Python.   You can specify how many bytes you want to read like shown in code…

Continue ReadingCommunication by pySerial python module in PSLab
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
Read more about the article Analyzing Sensor Data on PSLab

Analyzing Sensor Data on PSLab

PSLab Android App and Desktop app have the functionality of reading data from the sensors. The raw sensor data received is in the form of a long string and needs to parsed to understand what the data actually conveys. The sensor data is unique in terms of volume of data sent, the units of measurement of the data etc., however none of this is reflected in the raw data. The blog describes how the sensor data received by the Android/Desktop app is parsed, interpreted and finally presented to the user for viewing. The image below displays the raw data sent by the sensors Fig: Raw Sensor data displayed below the Get Raw button In order to understand the data sent from the sensor, we need to understand what the sensor does. For example, HMC5883L is a 3-axis magnetometer and it returns the value of the magnetic field in the x, y & z axes in the order of nanoTeslas. Similarly, the DAC of PSLab - MCP4728 can also be used like other sensors, it returns the values of channels in millivolts. The sensor MPU6050 being 3-axes accelerometer & gyroscope which returns the values of acceleration & angular momentum of the x, y & z axes in their SI units respectively. Each sensor has a sensitivity value. The sensitivity of the sensor can be modified to adjust the accuracy of the data received. For PSLab, the data returned is a float number with each data point having 4 bytes of memory with the highest sensitivity. Although sensitivity is not a reliable indicator of the accuracy of the data. Each value received has a lot of trailing values after the decimal and it is evident that no sensor can possibly achieve accuracy that high, so the data after 2-3 decimal places is garbage and not taken into consideration. Some sensors are configurable up to a great extent like MPU6050 where limits can also be set on the range of data, volume of data sent etc. whereas some are not configurable and are just meant for sending the data at regular intervals. In order to parse the above data, if the sensor returns a single value, then the data is ready to be used. However, in most cases like above where the sensors return multiple values, the data stream can be divided into equal parts since each value occupies equal space and each value can be stored in different variables. The stored data has to be presented to the user in a better understandable format where it is clear that what each value represents. For example, in case of the 3 axes sensors, the data of each axis must be distinctly represented to the user. Shown below are the mock-ups of the sensor UIs in which each value has been distinctly represented.           Fig: Mock-ups for the sensor UIs (a) - HMC5883L (b) - MPU6050 Each UI has a card to display those values. These values are updated in…

Continue ReadingAnalyzing Sensor Data on PSLab
Read more about the article Creating Multiple Device Compatible Layouts in PSLab Android

Creating Multiple Device Compatible Layouts in PSLab Android

The developer's goal is that PSLab Android App as an app should run smoothly on all the variety of Android devices out in the market. There are two aspects of it - the app should be able to support maximum number of Android versions possible which is related to the core software part and the other being the app should be able to generate the same user experience on all sizes of screens. This post focuses on the later. There are a whole range of android devices available in the market right from 4 inch mobile phones to 12 inch tablets and the range in the screen sizes is quite large. So, the challenge in front of app designers is to make the app compatible with the maximum  number of devices without doing any specific tweaks related to a particular resolution range. Android has its mechanism of scaling the app as per the screen size and it does a good job almost all the time, however, still there are cases where android fails to scale up or scale down the app leading to distorted layout of the app. This blog discusses some of the tricks that needs to be kept in mind while designing layouts that work independent of screen sizes. Avoid using absolute dimensions It is one of the most common things to keep in mind before starting any UI design. Use of absolute dimensions like px, inch etc. must be avoided every time as they are fixed in size and don’t scale up or scale down while screen sizes are changed. Instead relative dimensions like dp should be used which depend on the resolution and scale up or scale down. ( It’s a fair assumption that bigger screens will have better resolution compared to the smaller ones although exceptions do exist) . Ensure the use of correct layout/View group Since, android provides a variety of layouts like Linearlayout, Constrainedlayout, Relativelayout, Tablelayout and view groups like ScrollView, RecyclerView, ListView etc. it is often confusing to know which layout/viewgroup should be used. The following list gives a rough idea of when to use a particular layout or view group. Linearlayout - Mostly used for simple designs when the elements are stacked in ordered horizontal/vertical fashion and it needs explicit declaration of orientation. Relativelayout - Mostly used when the elements need to defined relative to the parent or the neighbouring elements. Since, the elements are relative, there is no need to define the orientation. Constraintlayout - It has all the features of Relativelayout and in addition a feature of adding constraints to the child elements or neighbouring elements. Tablelayout - Tablelayout is helpful to when all the views/widgets are arranged in an ordered fashion. All the above layouts can be used interchangeably most of the times, however, certain cases make some more favourable than others like when than views/ widgets are not present in an organised manner, it is better to stick to Linearlayout or Relativelayout. ListView - Used when the…

Continue ReadingCreating Multiple Device Compatible Layouts in PSLab Android
Read more about the article Using Sensors with PSLab Android App

Using Sensors with PSLab Android App

The PSLab Android App as of now supports quite a few sensors. Sensors are an essential part of many science experiments and therefore PSLab has a feature to support plug & play sensors. The list of sensors supported by PSLab can be found here. AD7718 - 24-bit 10-channel Low voltage Low power Sigma Delta ADC AD9833 - Low Power Programmable Waveform generator ADS1115 - Low Power 16 bit ADC BH1750 - Light Intensity sensor BMP180 - Digital Pressure Sensor HMC5883L - 3-axis digital magnetometer MF522 - RFID Reader MLX90614 - Infrared thermometer MPU6050 - Accelerometer & gyroscope MPU925x - Accelerometer & gyroscope SHT21 - Humidity sensor SSD1306 - Control for LED matrix Sx1276 - Low Power Long range Transceiver TSL2561 - Digital Luminosity Sensor All the sensors except Sx1276 communicate using the I2C protocol whereas the Sx1276 uses the SPI protocol for communication. There is a dedicated set of ports on the PSLab board for the communication under the label I2C with the ports named 3.3V, GND, SCL & SDA. Fig; PSLab board sketch Any I2C sensor has ports named 3.3V/VCC, GND, SCL, SDA at least along with some other ports in some sensors. The connections are as follows: 3.3V on PSLab - 3.3V/VCC on sensor GND on PSLab - GND on sensor SCL on PSLab - SCL on sensor SDA on PSLab - SDA on sensor The diagram here shows the connections For using the sensors with the Android App, there is a dedicated I2C library written in communication in Java for the communication. Each sensor has its own specific set of functionalities and therefore has its own library file. However, all these sensors share some common features like each one of them has a getRaw method which fetches the raw sensor data. For getting the data from a sensor, the sensor is initially connected to the PSLab board. The following piece of code is responsible for detecting any devices that are connected to the PSLab board through the I2C bus. Each sensor has it’s own unique address and can be identified using it. So, the AutoScan function returns the addresses of all the connected sensors and the sensors can be uniquely identified using those addresses. public ArrayList<Integer> scan(Integer frequency) throws IOException { if (frequency == null) frequency = 100000; config(frequency); ArrayList<Integer> addresses = new ArrayList<>(); for (int i = 0; i < 128; i++) { int x = start(i, 0); if ((x & 1) == 0) { addresses.add(i); } stop(); } return addresses; }   As per the addresses fetched, the sensor library corresponding to that particular sensor can be imported and the getRaw method can be called. The getRaw method will return the raw sensor data. For example here is the getRaw method of ADS1115. public int[] getRaw() throws IOException, InterruptedException { String chan = typeSelection.get(channel); if (channel.contains("UNI")) return new int[]{(int) readADCSingleEnded(Integer.parseInt(chan))}; else if (channel.contains("DIF")) return new int[]{readADCDifferential(chan)}; return new int[0]; } Here the raw data is returned in the form of voltages in mV. Similarly, the…

Continue ReadingUsing Sensors with PSLab Android App
Read more about the article Creating Custom Components in the PSLab Android App

Creating Custom Components in the PSLab Android App

PSLab Android App supports a lot of features and each of these features need components & views for their implementation. A typical UI of PSLab is shown in the figure below. Considering the number of views & components used in the figure, implementation of each view & component separately would lead to a huge volume of repetitive and inefficient code. As it is evident that the EditText and two buttons beside it keep repeating a lot, it is wiser to create a single custom component consisting of an EditText and two buttons. This not only leads to efficient code but also results in a drastic reduction of the volume of code. Android has a feature which allows creating components. For almost all the cases, the pre-defined views in Android serve our purpose of creating the UIs. However, sometimes there is a need to create custom components to reduce code volume and improve quality. Custom components are used when a particular set of component needed by us is not present in the Android view collection or when a pattern of components is frequently repeated or when we need to reduce the code complexity. The above set can be replaced by defining a custom component which includes an edittext and two buttons and then treating it like just any other component. To get started with creating a custom component, the steps are the following: Create a layout for the custom component to be designed <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="match_parent"> <Button android:id="@+id/button_control_plus" android:layout_width="0dp" android:layout_weight="0.5" android:layout_height="20dp" android:background="@drawable/button_minus" /> <EditText android:id="@+id/edittext_control" android:layout_width="0dp" android:layout_weight="2" android:layout_height="24dp" android:layout_marginTop="@dimen/control_margin_small" android:inputType="numberDecimal" android:padding="@dimen/control_edittext_padding" android:background="@drawable/control_edittext" /> <Button android:id="@+id/button_control_minus" android:layout_width="0dp" android:layout_weight="0.5" android:layout_height="20dp" android:background="@drawable/button_plus" /> </LinearLayout> The layout file edittext_control.xml is created with three views and each one of them has been assigned an ID along with all the other relevant parameters. Incorporate the newly created custom layout in the Activity/Fragment layout file <org.fossasia.pslab.others.Edittextwidget android:id="@+id/etwidget_control_advanced1" android:layout_height="wrap_content" android:layout_width="0dp" android:layout_weight="2" android:layout_marginLeft="@dimen/control_margin_small" android:layout_marginStart="@dimen/control_margin_small" /> The custom layout can be added the activity/fragment layout just like any other view and can be assigned properties similarly. Create the activity file for the custom layout public class Edittextwidget extends LinearLayout{ private EditText editText; private Button button1; private Button button2; private double leastCount; private double maxima; private double minima; public Edittextwidget(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); applyAttrs(attrs); } public Edittextwidget(Context context, AttributeSet attrs) { super(context, attrs); applyAttrs(attrs); } public Edittextwidget(Context context) { super(context); } public void init(Context context, final double leastCount, final double minima, final double maxima) { View.inflate(context, R.layout.edittext_control, this); editText = (EditText) findViewById(R.id.edittext_control); button1 = (Button) findViewById(R.id.button_control_plus); button2 = (Button) findViewById(R.id.button_control_minus); button1.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Double data = Double.valueOf(editText.getText().toString()); data = data - leastCount; data = data > maxima ? maxima : data; data = data < minima ? minima : data; editText.setText(String.valueOf(data)); } }); button2.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Double data = Double.valueOf(editText.getText().toString()); data = data + leastCount; data = data > maxima ? maxima : data; data = data < minima…

Continue ReadingCreating Custom Components in the PSLab Android App
Read more about the article Trigger Controls in Oscilloscope in PSLab

Trigger Controls in Oscilloscope in PSLab

PSLab Desktop App has a feature of oscilloscope. Modern day oscilloscopes found in laboratories support a lot of advanced features and addition of trigger controls in oscilloscope was one such attempt in adding an advanced feature in the oscilloscope. As the current implementation of trigger is not robust enough, this feature would help in better stabilisation of waveforms. Captured waveforms often face the problem of distortion and trigger helps to solve this problem. Trigger in oscilloscope is an essential feature for signal characterisation.  as it synchronises the horizontal sweep of the oscilloscope to the proper point of the signal. The trigger control enables users to stabilise repetitive waveforms as well as capture single-shot waveforms. By repeatedly displaying similar portion of the input signal, the trigger makes repetitive waveform look static. In order to visualise how an oscilloscope looks with or without a trigger see the following figures below. Fig 1: (a) Without trigger  (b) With trigger The Fig:1(a) is the actual waveform received by the oscilloscope and it can be easily noticed that interpreting it is confusing due to the overlapping of multiple waveforms together. So, in Fig:1(b) the trigger control stabilises the waveforms and captures just one waveform. In general the commonly used trigger modes in laboratory oscilloscopes are:- Auto - This trigger mode allows the oscilloscope to acquire a waveform even when it does not detect a trigger condition. If no trigger condition occurs while the oscilloscope waits for a specific period (as determined by the time-base setting), it will force itself to trigger. Normal - The Normal mode allows the oscilloscope to acquire a waveform only when it is triggered. If no trigger occurs, the oscilloscope will not acquire a new waveform, and the previous waveform, if any, will remain on the display. Single - The Single mode allows the oscilloscope to acquire one waveform each time you press the RUN button, and the trigger condition is detected. Scan – The Scan mode continuously sweeps waveform from left to right. Implementing Trigger function in PSLab PSLab has a built in basic functionality of trigger control in the configure_trigger method in sciencelab.py. The method gets called when trigger is enabled in the GUI. The trigger is activated when the incoming wave reaches a certain voltage threshold and the PSLab also provides an option of either selecting the rising or falling edge for trigger. Trigger is especially useful in experiments handling waves like sine waves, square wave etc. where trigger helps to get a clear picture. In order to initiate trigger in the PSLab desktop app, the configure_trigger method in sciencelab.py is called. The configure_trigger method takes some parameters for input but they are optional. If values are not specified the default values are assumed. def configure_trigger(self, chan, name, voltage, resolution=10, **kwargs): prescaler = kwargs.get('prescaler', 0) try: self.H.__sendByte__(CP.ADC) self.H.__sendByte__(CP.CONFIGURE_TRIGGER) self.H.__sendByte__( (prescaler << 4) | (1 << chan)) if resolution == 12: level = self.analogInputSources[name].voltToCode12(voltage) level = np.clip(level, 0, 4095) else: level = self.analogInputSources[name].voltToCode10(voltage) level = np.clip(level, 0, 1023) if…

Continue ReadingTrigger Controls in Oscilloscope in PSLab
Read more about the article Establishing Communication between PSLab and an Android Device using the USB Host API

Establishing Communication between PSLab and an Android Device using the USB Host API

In this post, we are going to learn how to establish communication between the PSLab USB device and a connected Android device. We will implement our own custom read & write methods by using functions provided by USB Host API of Android SDK. At first we need to enable communication to PSLab device by connecting it to Android Phone by an On-The Go (OTG) cable. We are communicating via the USB Host API of Android. About Android USB Android supports USB peripherals through two modes: Android Accessory: In this mode external USB device acts as host. Android Host: In this mode Android Device acts as host and powers the external device. Obtaining Permission to access USB device When a USB device is connected to Android device, you need to obtain permissions to access the USB device. You have two ways, I have used intent-filter method to obtain permission in PSLab project, but you can also use the approach to implement a broadcast receiver. Option 1: Add a intent filter in the activity which would handle that connected USB device. This is an implicit way to obtain permission. <activity ...> ...    <intent-filter>        <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />    </intent-filter>    <meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"        android:resource="@xml/device_filter" /> </activity> And add device details like your vendor ID and product ID in device_filter.xml <resources>    <usb-device vendor-id="1240" product-id="223" /> </resources> Now when you connect your USB device, permission dialog like below would pop up: Option 2: If you want to obtain permission explicitly, first create broadcastreceiver which would be broadcasted which you call requestPermission(). private static final String ACTION_USB_PERMISSION =    "com.android.example.USB_PERMISSION"; private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {    public void onReceive(Context context, Intent intent) {        String action = intent.getAction();        if (ACTION_USB_PERMISSION.equals(action)) {            synchronized (this) {                UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);                if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {                    if(device != null){                   }                }                else {                    Log.d(TAG, "permission denied for device " + device);                }            }        }    } }; Register this broadcastreceiver in your onCreate method of your activity. UsbManager mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE); private static final String ACTION_USB_PERMISSION =    "com.android.example.USB_PERMISSION"; ... mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0); IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION); registerReceiver(mUsbReceiver, filter); And call requestPermission method to show a dialog for permission UsbDevice device; ... mUsbManager.requestPermission(device, mPermissionIntent); Now when you open your App permission dialog like shown below would pop up: Obtain Read & Write Endpoints Now that you have permission to communicate with a USB device connected. Next step is to obtain read and write Endpoints to read and write to USB device by using bulkTransfer() function. The definition of bulkTransfer() methods is int bulkTransfer (UsbEndpoint endpoint,                byte[] buffer,                int length,                int timeout) endpoint : Usb Endpoint ( the endpoint for this transaction ) buffer : byte ( buffer for data to send or receive ) length : int ( length of data to send/receive ) timeout : int ( in milliseconds, 0 is infinite ) For code to obtain read, write Endpoint through Data Interface of USB device. Open() method of PSLab can be referenced. There are two ways for communication…

Continue ReadingEstablishing Communication between PSLab and an Android Device using the USB Host API
Read more about the article How to Collaborate Design on Hardware Schematics in PSLab Project

How to Collaborate Design on Hardware Schematics in PSLab Project

Generally ECAD tools are not built to support collaborative features such as git in software programming. PSLab hardware is developed using an open source ECAD tool called KiCAD. It is a practice in the electronic industry to use hierarchical blocks to support collaboration. One person can work on a specific block having rest of the design untouched. This will support a workaround to have a team working on a one hardware design just like a software design. In PSLab hardware repository, many developers can work simultaneously using this technique without having any conflicts in project files. Printed Circuit Board (PCB) designing is an art. The way the components are placed and how they are interconnected through different type of wires and pads, it is an art for hardware designing engineers. If they do not use auto-route, PCB design for the same schematic will be quite different from one another. There are two major approaches in designing PCBs. Top Down method Bottom Up method Any of these methods can be implemented in PSLab hardware repository to support collaboration by multiple developers at the same time. Top Down Method In this method the design is starting from the most abstract definitions. We can think of this as a black box with several wires coming out of it. The user is aware of how to use the wires and to which devices they need to be connected. But the inside of the black box is not visible. Then a designer can open up this box and break the design down to several small black boxes which can perform a subset of functionalities the bigger black box did. He can go on breaking it down to even smaller boxes and reach the very bottom where basic components are found such as transistors, resistors, diodes etc. Bottom Up Method In the bottom up method, the opposite approach of the top down method is used. Small parts are combined together to design a much bigger part and they are combined together to build up an even bigger part which will eventually create the final design. Our human body is a great example for a use of bottom up method. Cells create organ; organs create systems and systems create the body. Designing Top Down Designs using KiCAD In PCB designing, the designers are free to choose whatever the approach they prefer more suitable for their project. In this blog, the Top Down method is used to demonstrate how to create a design from the abstract concepts. This will illustrate how to create a design with one layer deep in design using hierarchical blocks. However, these design procedures can be carried out as many times as the designer want to create depending on the complexity of the project. Step 01 - Create a new project in KiCAD Step 02 - Open up Eeschema to begin the design Step 03 - Create a Hierarchical Sheet Step 04 - Place the hierarchical sheet on the design sheet and give it…

Continue ReadingHow to Collaborate Design on Hardware Schematics in PSLab Project