Exploring raspberry pi pdf download

Because CMOS devices support a wide range of supply voltages, the signal levels are generally understood on the basis of percentages. CMOS Voltage for 3.

Because CMOS inputs require no current to drive, the signals are extremely compatible provided that the circuit is not loaded down with extras like an LED being driven. Because CMOS gates consume almost no current, there is a virtually unlimited fanout capability fanout is the capability of one logic device to drive the inputs of others. Problems begin when you combine logic signals with loads that require current. With a bit of planning and insight, these problems are easily avoided.

Solutions for this problem include the following: 1. Increasing the resistance of R1 to reduce the load this also decreases brightness of the LED. When the Drive0 has a 1 bit configured, there is an additional help of 2 mA drive for a total of 4 mA. If you were to configure Drive2 as a 1 bit, then an additional 8 mA of drive is added, for a total drive capability of 12 mA.

The Raspberry Pi can provide up to 16 mA of total drive. GPIO 0 to 27 8 mA at reset 2. GPIO 28 to 45 16 mA at reset 3. The gp command option -S permits you to change the drive strength for Groups 1 and 2. All inputs must go somewhere. Protect the protection. For static precautions, Lancaster says: Any and all of these methods give good in-circuit protection against static problems.

They also will give you good out-of-circuit protection, provided you are reasonably careful with your handling of the devices.

Most lists of rules for handling MOS devices are overdone and introduce more problems than they solve. To take care of MOS circuits, keep them in conductive foam or metal carriers before use, and solder them in place with an ordinary small soldering iron.

Make sure your circuits have some sort of input resistor for MOS leads going off the pc board. Figure shows a photo of a low-cost antistatic wristband available from eBay for as little as a dollar. Insert your hand in the wrist band and then attach the clip to something grounded. This helps to bleed off any static electric charges that might accumulate as you move around.

Antistatic wristband Also use common sense with clothing when you know you will be working with these parts. Some synthetic materials are very bad for static electricity.

Avoid working on carpets if possible. Keep them away at all costs, especially in dry weather. One of our cats only had to look at my Pi before it crashed and reset.

Summary To the nonelectronics reader, congratulations! The resistor solution permits you to safely use a GPIO pin that might be misconfigured at boot time. This gives you greater freedom in your designs.

Finally, the review of logic voltage levels has prepared you for avoiding the pitfall of combining loads with logic signal interfaces. Bibliography [1] Lancaster, Don, and Howard M. CMOS Cookbook. Indianapolis, IN: H. Sams, This was necessary to install the rpidma kernel driver so that the pispy command could allocate and use DMA for data capture.

In this chapter, we turn our attention to the pispy tool itself and learn how to use it. We also take a high-level look at how it works. Much of what we do in this book involves GPIO inputs and outputs in some form or another, but programming GPIO pins can be quite a chore if you must do it blind. A digital oscilloscope allows you to see the inputs and outputs as they change over time. Capture is the first part of the operation. The pispy tool automatically invokes GtkWave to display the captured results graphically you also can invoke GtkWave manually.

Because GtkWave is a package, you might need to install it. Done Building dependency tree Reading state information Most of them have to do with triggering, which we look at later.

Capture Length The first decision you need to make is how long to capture data for. Data is captured in 64K byte blocks. Each sample requires 4 bytes 32 bits , so this means that 16, samples are captured in each block. Using a nonoverclocked Raspberry Pi 2, the samples are captured at a rate of about every More about this sampling rate follows later.

This means that one block of capture takes about 1. To eliminate this problem, pispy uses the kernel mailbox facility to allocate blocks of memory from the GPU. The allocated GPU memory is only used during the capture and is then returned. Capture Resolution In the preceeding section, we noted that the capture occurs at about the rate of every But as you experiment, you will confirm that the highest actual sample rate that you can capture is about 1 MHz.

This is due to the fact that the sampling rate provided by the DMA occurs at a higher rate than the internal GPIO circuitry can read changes. However, one important piece of information is the number of interrupts 1 here.

There should be one interrupt for each 64k block of captured data. Option -x By default, pispy invokes gtkwave automatically after the capture. You simply capture a certain amount of time and display the signal. For other types of signals, however, there can be hundreds of milliseconds between interesting events. Trying to capture the interesting part can be challenging without a triggered capture.

The pispy tool supports a limited form of triggering. So what are the limitations? This is faster and more reliable than trying to do so from software. Once we set up the DMA control block s and unleash it, the DMA peripheral rips through its control blocks at breakneck speed.

We can only start or abort a DMA transfer. So pispy performs the following to implement trigger functionality: 1. Set up DMA control blocks and start the capture.

While the DMA continues for multiblock captures , pispy examines the first block for a trigger event. If the trigger event has been found in the first block, the capture is permitted to run to completion. Otherwise, pispy aborts the current DMA capture. If the number of tries have not been exceeded option -T , repeat from Step 1. For this reason, triggers must also provide a number of tries using the -T option. If you run pispy from the desktop, or using an X Window session in ssh, pispy will invoke gtkwave automatically unless the -x option was provided.

When using ssh, be sure to add the -X option. If your captured data is interesting from Monday, though, you might want to review it again on Tuesday. After you know what to do, though, things work rather well. The first worry that you have when you open it like this, is that it appears to have no information!

Use your mouse and click Top in the top left window of the display. This should highlight Top and show signals in the window below after you do this.

Figure shows how all of the GPIO signals become available in the window below. This will get some sort of a plot going in the black window labeled Waves. Note that more than one signal can be dragged and displayed when needed. It will have a dotted line box in it. Clicking this causes the time to be rescaled to match the entire capture. You can then zoom in by clicking the magnifying lens buttons as required or scroll the Waves window scroll bar.

Make sure you have nothing attached to GPIO 12 for this experiment. Rescale the time and you should see a wave form looking like Figure your wave form might look smaller in height; see the next section. You can, of course, drag multiple GPIO signals to the display. One thing you might notice is that the captured. This is because the file format is used only to record changes in signal. Unless there is significant signal change activity, the VCD file will be smaller.

With increasing age, we all eventually suffer from the difficulty of not seeing things up close or things that are too small. The lens becomes hard and inflexible. Whatever the cause, we can make that wave form a bit more vertically prominent by cheating—by increasing the font size of the Signals window.

An increase in font size causes the wave form height to increase with it. Create a file in your home directory named. In it, put the line shown below modify it to suit your own tastes. The line configures the choice of font and a size for it. Choose Cut and the signal will be removed.

With this overview, and the provided source code, the keen programmer can reuse the classes found in librpi2 for his or her own programs.

Logic Analyzer include "logana. GPIO include "gpio. The other classes can be used by the enterprising programmer simply by reviewing the include files for them. The following basic steps are used by the pispy program to capture and display the signals: 1. Parse command line options. This causes the following to happen: 1. Opens this driver file. Allocates pages for the mailbox. Locks that memory.

Obtains a virtual address for the mailbox memory. If the verbose -v option is used, the first control block is displayed on the terminal. If there are triggers involved, the code waits for the first DMA interrupt to occur. This signals that the data in the first capture block is ready for scanning.

If there are triggers and the trigger condition is found in the first capture block, the capture is allowed to continue until completion. Otherwise, the current DMA capture is aborted and restarted. The loop will give up if the trigger is not found in so many tries -T option. If the verbose option is used -v , the final DMA status is reported to the terminal session.

At this point the capture is complete and sitting in memory. The next thing that happens is that the data captured is written out to a file. It defines signals gpio0 through to gpio31, and writes out timing and change information. This information can then be loaded and viewed directly by the gtkwave command.

Because gtkwave spits out a lot of GTK messages at startup, these are either suppressed or sent to the file. Summary In this chapter you learned how to apply pispy to capture GPIO signals into a file named captured.

You also learned how to operate gtkwave, which is perhaps less than obvious to use. Finally, the gtkwave customizations provided could be a great help to some. The next chapter introduces you to the piclk command provided with this book. Use a push button and a couple of connections and some simple software to read a 1 or a 0, right?

It all seems so elementary, yet things are more complicated than that. What actually happens goes against intuition because we think and operate more slowly than a digital circuit. The physical action of pushing a button might require a half-second or so, so we tend to think in those terms.

On the other hand, a digital circuit can react to a million of events in the same time frame. This chapter explores the push button and the problems it poses to electronic inputs. This chapter introduces students to some simple hardware solutions to the problem. At rest, the signal is low reading as 0. When pressed, the signal transitions to high 1 and remains high as long as the button is pressed.

Figure was a signal captured by PiSpy from a push button employing a debounce circuit. Ideal debounced button press Figure shows the result of a low-quality button closing. You can see that the contacts close near time 0, and go high and low several times, as the metal contacts bounce on and off.

Much later the contacts eventually settle. A bouncing pair of button contacts Here is the insidious part: Buttons are being improved all the time, so you could wire your own button up to a GPIO and it might seem to work okay, at least some of the time. Here is an experiment.

This is in part due to the low sampling rate of the Raspberry Pi running the gp command a CMOS counter chip on the other hand, might register several counts.

If you want to simulate a scratchy button, take two alligator clips or wire ends and touch them together. For buttons, however, the flip-flop circuit is inconvenient because it requires both normally open and normally closed contacts.

This mandates more expense and additional wiring. A simpler and more economical solution is shown in Figure , using a Schmitt trigger CD in this case. The button is represented by S1, connected to resistor R1 and capacitor C1. Pressing the button places a low signal at the input of IC1A. Because it is an inverter, a high output is produced while the button is pressed. An advantage of the hex inverter part like the CD means that you get six of these for the price of one.

A momentary button debounce circuit Toggled Debouncing Switches can be expensive to buy and install in quantity. Buttons, on the other hand, can sometimes be inexpensive by comparison. If you were able to use a button to toggle a signal, you could use a button as a switch. Alternatively, you could add one more inverter to be used as a buffer stage. When using the circuit shown in Figure , the application normally requires some sort of feedback to the user.

If the Raspberry Pi application shows something visual on a screen, other LED, or sound in response to a button press, then nothing further is needed.

However, if none of these cues are present, the user will be wondering if he or she toggled the input on or off. Figure shows one possible solution to the problem, at the expense of more components. These extra inverters may be drawn from IC1 if you prefer this schematic was extracted from a larger design that I used.

Normally the resistor is required and it is still good practice to use it. Here, it is possible to get away without it if you like because the circuit for the Raspberry Pi will be operating from 3. Additionally, the CMOS output transistor itself will be limited in the current that it can deliver at this lower voltage level.

So be certain to choose a small, low-current LED for the purpose. The MC The contact bounce problem was serious enough to have a chip designed for the purpose. Again, 3. The complexity of these chips probably contributes to their higher price compared to other logic gates in the series I purchased mine from eBay for about a dollar each. The MC works on a sampling principle. It clocks in samples of the input at intervals, arriving at an on or off conclusion at its output pin. If the internal shift register shows that the samples all agree as zeros contacts closed , then the output goes low 0.

Conversely, if the shift register now shows the samples all as high contacts open the output changes to high 1. Changes due to jitters in the input signal are thus ignored at the output. Figure shows a circuit with two push buttons buttons for BIN through EIN are not not shown but could also be wired. The MC has built-in internal pullup resistors for inputs, so none are required externally use care for static electricity in your handling, however.

The datasheet provides formulas for C1, for a given sampling frequency. The next larger standard size of capacitor would thus be 0. Some experimentation might be required. It produced a higher sampling frequency, which would make it more sensitive to button glitches, but it proved the overall operation okay with no problems.

Using PiSpy, I was able to sample the oscillator output on pin 9. You need a long sampling period due to the low frequency of the oscillator. I chose to use 48 blocks -b48 for this capture. From the gtkwave output in Figure , you can see that the wave form period was about 32 ms. Taking the reciprocal of that gives us a frequency of about Note that GPIO 19 boots up as an input, but otherwise make sure that it is in input mode with gp -g19 -i -pu before making the connection -pu adds a pullup resistor, which also should be the default.

Once the gp command is monitoring, you should be able to get clean button press events. Figure illustrates my breadboard test on the end of the Raspberry Pi 2 workstation. This circuit is so easy to breadboard that you should make a point of trying it yourself. It simply needs 3. The output simply goes to a GPIO input.

Breadboard setup for MC button test When ordering this part, buy more than one I suggest five. If you experience trouble getting this to work like I did the first time , perform the following checks: 1. Check ground. Check pin Check the capacitor: Are the connections pin 7 and pin 9? Disconnect the push button and the GPIO wire.

Powering the unit again, using PiSpy you should be able to capture a wave form. If the frequency is extremely low, you might only capture the signal going high, or returning low. Either way, this is a good sign that the oscillator is operating perhaps too slowly.

Once the oscillator is known to be operational, you should be able to hook up a button and see the output change with button presses. You can hook up a GPIO pin or use a multimeter on the output pin.

Manufactured buttons are pretty good these days, but they can still provide shaky contact and release signals. Without debounced inputs, the interface might work fine until you go to demonstrate it someday. This chapter has highlighted three different circuits for debouncing. I encourage you to try them all on a breadboard.

This list is by no means exhaustive, but these should be easy to replicate. The first was a simple way to produce a debounced momentary push button input using Schmitt triggers. It required only a resistor and capacitor for analog components. The second circuit is interesting because it allows you to use a button as a switch by toggling the output with each button press.

It does have the disadvantage of needing user feedback and requires more components. The final circuit, using the MC, is perhaps the easiest to use of them all. It requires only one analog component capacitor and provides six debounced outputs. Those with low patience for history and the theory will like the approach of jumping in and getting started. When you see the STL used in simple digestable examples, the fear and loathing will evaporate.

The C language was standardized. This is free software; see the source for copying conditions. You will need at least version 4. If necessary, install version 4.

If this is failing, replace that line with a hard-coded reference to the compiler you want to use. One of the subtle changes is that the C language struct is now in the same namespace as all other types.

Consider the following C language example a program named t. If I rename the program file t. This confirms that the struct name and the typedef names are in the same namespace. Why is this important? You can simply use the structure name like any other type. The only difference between them is that all members of a structure are public unless otherwise modified by the keywords private or protected.

By way of contrast, class definitions are all private unless otherwise specified. At the same time, the STL leverages well-tested code, avoiding costly debugging: no more handcrafting lookup tables, debugging of memory leaks, and so on.

Throw away your ancient STL book and open this site with your browser while you code. Figure shows the home page of the site. Home page for cplusplus. Click the Reference link to expand its options. Figure illustrates how the Reference section opens up. All of these problems vanish when you use the std::vector container. The std::vector is a class that wraps around an array and manages its memory space and size.

To use a vector to hold an array of int type, simply include the header file and declare it. The actual size of this internal array might be 8 initially, but the object myvec knows that its current size is now 1.

If you keep adding values, the object could double its capacity to 16 internally to allow for future growth, when you add the ninth value. When the object myvec goes out of scope, the storage associated with myvec is automatically freed, thanks to the built-in object destructor. No more memory leaks! Once you have a vector, you often need to iterate it; that is, visit each entry as if it were an array.

With the vector, there are actually two ways to do this. The first is nearly identical to the C language way, using subscripting. The main idea is that you get the current size of the vector from myvec. Because the template argument allows you to specify other data types, you can declare vectors of other types including struct and class. This can be done using the myvec. We also supply myvec. As a note of caution, however, if you add or delete members from the vector, the internal array can be reallocated.

However, WiMax are chosen because it ZigBee is mostly used in low data a rate application that does overcomes both distance limitation of Wi-Fi and the absence of not require high power consumption and secure transmission. They provide result to prove that the system is user ZigBee networks use of bit symmetric encryption keys friendly and effective to protect over hail and maintenance cost.

In this project, Raspberry Pi is used as a server by connecting to several laptops as clients in the same network. The work was There is various kind of existing application such as wireless explored in three different scenarios, i. Client-server communication equipment etc. Client-server communication within communication such as ZigBee. ZigBee is considered better localhost for remote file sharing facility. Router is used to than other technology Bluetooth or Wi-Fi because it is create a wireless network communication between the devices.

To create remote file sharing environment, wireless adapter and 2. Mohamed Noor has conducted work on communication platform. In order to carry out the research, community based home security using wireless mesh network several hardware and software platforms were required as [15].

In this work, the author builds a prototype for home shown below. The system is considered cost effective and scalable. It is 3. It acts as a file server in this shared among house residential. The system can Pi Wifi connection. Client-Server Communication using Wi-Fi In this experiment, client-server communication is explored by transferring file wirelessly to the server using Wi-Fi communication.

Raspberry Pi supports wireless communication by allowing connection to wireless adapter. In order to set up a server in Raspberry Pi, samba software is used by setting configuration such as permit user to read only, write only or read write access. Raspberry Pi has features to allow for path: is the folder location for sharing file. The XBee manufacturer, once called maxstream, now 'Digi', built software called X-CTU and it works on all versions of Figure 1 shows the overall system architecture of client server windows.

Figure 3 shows the basic installation file in raspberry pi server. Figure 7 show the testing communication with XCTU. Figure 3 Installation of XCTU The installation process for this program is just like any other, so can download and get it installed in the laptop or desktop. Next, two XBee and a Raspberry Pi is used to setup the communication environment. In order to communicate XBee with the Raspberry Pi, Minicom must be installed and configured correctly [19].

The tool Minicom can be downloaded through Aptitude. After installation, the following steps are required to configure the XBee. I gather this has changed since 4. Otherwise all is well. Hope this helps a few out there. In an endeavour to fully progress through your book, could you confirm which RPi and software the book was actually used for testing the programmes?

My aim is then to configure an identical RPi, to complete the book and then explore the GPIO programming across the versions. I must confess that it is this variety of GPIO configurations that is confusing me, and probably many other readers and any help would be welcome. You might want to add information around page 30 to tell new users how to enable ssh. Refer to the following link. Great book by the way! I just got the Raspberry Pi 3B, and plan to go through your book to familiarize myself with the capabilities and uses of the device.

Do you recommend installing Stretch or Jesse as the better platform for the code examples in the book, or are both equally compatible? The comment below the code isn't quite accurate … rather "ORing 0" e. Interfacing to the Real World with Embedded Linux. About the Book. The Book. Purchase the Book:. Source Code. Technical Editor.

BibTeX Citation. Jim Silas July 1, at pm. Vidal Junior July 6, at am. Andrew N. Sloss July 10, at pm. Hello Derek, What a great book!. Kind regards, —andrew.

Charles Liggett August 6, at am. Milliwaysi September 4, at am. Hello Derek, Great book!. Thank you very much. DeWayne Warden October 4, at pm. Malloy, Thank you for such a wonderful book. Regards, DeWayne. Hi Derek, I am about two weeks into the book and like it very much.

Don Grove April 25, at pm. Hi Derek, I am now getting into more of the hardware integration in your book Exploring Raspberry Pi. Keith Gillett May 2, at pm.

Dave Murray May 17, at am. Hi Derek, I love your book and have recommended it to others. Best regards, Dave Murray. This book was released on 09 June with total page pages. Book excerpt: Expand Raspberry Pi capabilities with fundamental engineering principles Exploring Raspberry Pi is the innovators guide to bringing Raspberry Pi to life.

This book favors engineering principles over a 'recipe' approach to give you the skills you need to design and build your own projects.