Hacking Roomba - Tod E.Kurt Part 4 potx

72 Part I — Interfacing F IGURE 4-4: Parts needed for this project Step 1: Preparing the Cable The Mini DIN 8-pin cable preparation is exactly the same as for the serial tether. Cut the cable about six inches from the Mini DIN connector. To get at the wires, strip off about two inches of the cable’s big plastic sheath and then strip off about 1/4˝ of the plastic insulation from all the wires inside. It usually helps to put the cables in the third-hand clamp tool before continuing. Using the soldering iron, lightly tin each wire with solder. Perform a continuity test on each wire to figure out which colored wire goes to which pin on the jack. It seems every Mini DIN cable has had a different color-to-pin mapping. Even if you’ve built the serial tether, don’t assume the color-to-pin mapping you discovered when building it applies to another Mini DIN cable. Even different ends of the same cable can have different pinouts. Refer to the left side of Figure 3-8 for details. Step 2: Laying Out the Parts The BlueSMiRF constrains the part layout, since it is so long and flat. Place the black header receptacle at one end of the circuit board facing in, so the circuit board provides some support 73 Chapter 4 — Building a Roomba Bluetooth Interface to the BlueSMiRF. You may want to cut down the 8-pin receptacle to a 6-pin one to save space. With the header placed, arrange the voltage regulator and the other parts so you can minimize the number of wires needed to solder. Figure 4-5 shows one possible layout, with the BlueSMiRF plugged into the receptacle to gauge the layout. Notice that the header receptacle has been cut down to be 6-pin, and the pins have been bent at a right angle so the receptacle lays flat against the board. F IGURE 4-5: Laying out the parts Step 3: Soldering When you have a layout you think you like, turn the board over and start soldering things down. When soldering the header receptacle, remove the BlueSMiRF so you don’t damage it. The whole point of the receptacle is to keep the BlueSMiRF away from the harshness of cir- cuit building. Figure 4-6 shows the previous layout mostly soldered down. Notice the small jumpers made from cut part leads (the horizontal silver-colored wires soldered between pads). The figure also shows the cable beginning to be attached to the board. 74 Part I — Interfacing F IGURE 4-6: Soldering down the parts Step 4: Checking Voltages As in the serial tether, when things are soldered down, you should hook up the wall wart power supply and test the voltages. See the section “Step 4: Checking Voltages” in Chapter 3 for more details, as the process here is almost exactly the same as there. Your standard DC wall wart of around +9V to +24V is used to emulate the Vpwr +16V power coming from the Roomba. The 78L05 voltage regulator will turn that unregulated voltage into the +5VDC needed by the BlueSMiRF and the LED. Using the test points created, hook up the multimeter to Vcc and GND. Connect the wall wart power supply to the Vpwr and GND test points on the circuit. The LED should light up. If it doesn’t, disconnect power immediately and check to find out why. Usually it’s because the LED is wired backward. If the LED lights, the multimeter should read 5V. When Vpwr is verified, check all the pins of the BlueSMiRF header receptacle. Pay particular attention when testing the voltages in the header receptacle. It should only have +5V going to it, and only on the one header socket meant for +5V. Step 5: Soldering the Cable This project is also easier than the last one because you only have to prepare and solder down one cable, the Mini DIN 8-pin that will plug into the Roomba. The same technique in Step 5 of the previous chapter applies here, too. Figure 4-7 shows the Bluetooth adapter almost com- plete. To make it more manageable and to give the cable some strain-relief in case it is pulled, hot glue it to the edge of the board. For an extra bit of added protection, before hot gluing, 75 Chapter 4 — Building a Roomba Bluetooth Interface loop some stray insulated wire around the cable and into the circuit board holes and twist tight. Also, add a bit of hot glue to the header receptacle to secure it to the board so plugging and unplugging the BlueSMiRF doesn’t stress the solder joints. With the cables and header receptacle secured down with hot glue, solder the wires and recep- tacle pins down. In general you want to secure connectors and wires before soldering them so any flex of those parts doesn’t affect the solder joints. F IGURE 4-7: The Mini DIN 8-pin cable soldered down Step 6: Testing Connections The adapter is now complete. However, before plugging in the BlueSMiRF and connecting it to the Roomba, perform one last set of continuity and voltage checks. When they check out, plug in the BlueSMiRF and power the circuit with the wall wart power supply in lieu of the Roomba. The LED should still light and the BlueSMiRF shouldn’t get warm or smoke or do anything else bad. If you’re measuring the current consumption of the entire circuit, it shouldn’t be more than 50 mA. If you’re measuring the voltage output of the regulator, it should still be at 5V. If it drops, disconnect power immediately. All of this testing and retesting may seem overkill, but it would be a shame to fry a BlueSMiRF. In addition to being cute, they are a little 76 Part I — Interfacing expensive to destroy. After getting used to performing these kinds of tests, doing them for other projects becomes faster and basically second nature. Figure 4-8 shows a finished Roomba Bluetooth adapter, tested and ready to be plugged into the Roomba. You may notice that this adapter is slightly different than the one in Figure 4-7. I have created many of these, each with slightly different layouts, but they all implement the same schematic and work the same. At this point the Bluetooth adapter and the serial tether should act exactly the same when plugged into the Roomba. That is, they’ll both light their LEDs and the Roomba is otherwise still usable. F IGURE 4-8: The finished circuit Step 7: Putting It in an Enclosure Every project needs an enclosure. Following the dental floss idea from the previous project, this project uses one too. Figure 4-9 shows the adapter in its new home, plugged into the Roomba and ready to go. Of course, a blue dental floss box seems perfect for a “blue-tooth” adapter. One side effect of using floss containers for all your projects is you accumulate more floss than you could ever use. So an alternative enclosure is shown in Figure 4-10. This enclosure is made from a blue container for a sugary grape-flavored gum that comes rolled up in a meter-long length. So it’s still a “blue-tooth” adapter. 77 Chapter 4 — Building a Roomba Bluetooth Interface F IGURE 4-9: Bluetooth adapter in a “blue-tooth” enclosure F IGURE 4-10: Another “blue-tooth” enclosure, only this time sweeter 78 Part I — Interfacing Setting Up Bluetooth In order to talk to the Roomba Bluetooth adapter, you need to configure Bluetooth properly on your computer. If your computer doesn’t have Bluetooth support built in, you’ll need to get a small USB Bluetooth interface fob (which costs less than $20). The steps are: 1. Install the USB Bluetooth interface on your computer (if it isn’t built-in already) 2. Install the drivers for the interface (may be already installed if built in). 3. Search for and pair your computer with the Roomba Bluetooth adapter. 4. Create the virtual serial port on the paired device. 5. Configure the Roomba Bluetooth adapter. In Windows, all those steps look incredibly different depending on which Bluetooth interface and which variant of Windows is used. In Mac OS X, it’s all standardized, even when using an older Mac without built-in Bluetooth support. The screenshots throughout this section show the steps in OS X, but be assured they are the same in Windows, even if they look different. In Windows, Steps 1 and 2 are the standard hardware install process, complete with reboot after installation. For OS X the drivers are already installed even for non–built-in Bluetooth inter- faces. So I’ll skip Steps 1 and 2 and go directly to Step 3. Pairing with Roomba Bluetooth Adapter Pairing is the mechanism Bluetooth devices use to securely recognize each other. The first time this is done it requires a human to help out. Plug the Bluetooth adapter you just made into the Roomba (or into the wall-wart power supply; it doesn’t matter for these tests). Then open the Bluetooth Preferences dialog box, turn on Bluetooth, and click Set Up a New Device. You’ll see a screen similar to the one shown in Figure 4-11, asking to choose the device type. These are the most supported Bluetooth profiles mentioned earlier. Since the Serial Port Profile isn’t listed, select Any Device and click Continue. The computer starts scanning for Bluetooth devices and the Roomba Bluetooth adapter should be in the list as shown in Figure 4-12. It is listed as BlueRadios or BlueSMiRF. Select it and click Continue. At this point the computer attempts to pair with the BlueSMiRF in the Roomba Bluetooth adapter. The BlueSMiRF responds that to pair it needs a passkey. That brings up the next screen, asking for a passkey. The default passkey for all BlueSMiRF devices is the string default. Type that in as shown in Figure 4-13 and click Continue. If you’ve used Bluetooth much, you’ve seen that passkeys are usually numeric. If you are on Windows and you’re given the option to save the pairing passkey, be sure to select Yes so you don’t have to type in the passkey default each time. 79 Chapter 4 — Building a Roomba Bluetooth Interface F IGURE 4-11: Starting up Bluetooth Setup Assistant F IGURE 4-12: Bluetooth devices found after scanning 80 Part I — Interfacing On Mac OS X 10.3 (Panther) and earlier, you can only input numeric passkeys. The best solution is the upgrade to Mac OS X 10.4 or higher. If you cannot upgrade, see the BlueSMiRF datasheet for how to change the passkey it uses by default to be a numeric one. F IGURE 4-13: Typing in the BlueSMiRF passkey The Mac OS X Bluetooth Setup Assistant then gets a little confused because it does not find a GUI setup agent for serial ports. This is fine; just ignore it and click Continue. In contrast, the Windows pairing just does its job without the somewhat confusing message. At this point, setup is done and you can go back to the known Bluetooth device list and see the BlueSMiRF (or BlueRadios). The screen should look similar to the one in Figure 4-14. Creating Bluetooth Virtual Serial Port Select the newly paired BlueSMiRF from the device list and click Edit Serial Ports. You should see a window similar to Figure 4-15. If you do not see the same info, change it so it matches. In Mac OS X, all serial port devices have unique names. For virtual serial ports, the name is constructed from the device type. So in the example BlueRadios-COM0-1, the device type is BlueRadios-COM0 and it’s the first one of that type. (COM0 is the first serial channel for BlueRadios; apparently there can be others.) Click OK and the virtual serial port is ready to use. In Windows, you’ll have to go through the extra step of binding the virtual serial port to a COM port (like COM7 or another unused port). The Bluetooth software for your adapter should help with this. Whichever COM port it is, remember it, because you’ll need to know it later. 81 Chapter 4 — Building a Roomba Bluetooth Interface F IGURE 4-14: The BlueSMiRF device is now known and paired. F IGURE 4-15: Creating a virtual serial port [...]... parsing of the command-line arguments, is in Listing 5-2 Controlling Roomba is getting easier Listing 5-2 : A Condensed Drive.java String portname = “/dev/cu.KeySerial1”; int velocity = 500, radius = -1 , waittime = 2000; RoombaCommSerial roombacomm = new RoombaCommSerial(); if( !roombacomm.connect(portname) ) System.exit(1); roombacomm.startup(); roombacomm.control(); roombacomm.pause(100); roombacomm.drive(velocity,... plug into a high-current motor driver The motor driver is controlled by the Roomba s microcontroller through a digital-to-analog (D/A) converter with approximately 10-bit resolution in this chapter Roomba drive system internals ROI DRIVE command Grow RoombaComm Move Roomba with RoombaComm 90 Part I — Interfacing FIGURE 5-1 : Roomba drive motor unit The other four wires are used to sense the wheel’s rotation... this chapter shows a taken-apart Roomba motor unit and discusses the gearing and other mechanisms Because the following figures show a taken-apart Roomba, there is no need for you to take a screwdriver to your own Roomba The whole point of the ROI (and this book) is to allow Roomba hacking without voiding your warranty If, however, you don’t mind having a potentially non-working Roomba at the end, I highly... sign of the velocity and radius values, there are four different ways the Roomba can move in a curve (see Figure 5 -4 ) status +velocity +radius power -velocity +radius clean spot max -velocity -radius +velocity -radius dirt detect FIGURE 5 -4 : Types of turns depending on the sign of radius and velocity The turn radius always makes the Roomba travel along a circle The only exceptions to this are the three... special-case movements 40 m m Roomba has a wheelbase diameter (the distance between the centerline of its two drive wheels) of 258 mm The diameter of the Roomba itself is around 340 mm (see Figure 5-5 ) All turning motion is based off of the 258 mm wheelbase (The front caster wheel is not used for turning; it’s a free spinning wheel that skids during non-straight turns.) ~3 94 258 mm Roomba FIGURE 5-5 :... package name for all RoombaComm code can be just roombacomm The library then can consist of a base class called roombacomm.RoombaComm In this base class you can put all the communication protocol-independent functions You can then make subclasses of it, like roombacomm.RoombaCommSerial and roombacomm.RoombaCommTCPClient, to implement the additional functionality needed to talk to a Roomba over a serial... any RoombaComm program: String portname = “/dev/cu.KeySerial1”; RoombaCommSerial roombacomm = new RoombaCommSerial(); if( !roombacomm.connect(portname) ) { System.out.println(“Couldn’t connect to “+portname); System.exit(1); } roombacomm.startup(); roombacomm.control(); roombacomm.pause(100); This chunk of code does several important things: Ⅲ Specifies a serial port to use by name Ⅲ Creates a new RoombaCommSerial... following section for more information on echo tests with BlueSMiRF.) Figure 4- 1 6 shows the results when using ZTerm That magic incantation changes the baud rate of the BlueSMiRF to 57,600 bps 8N1, which is what Roomba expects FIGURE 4- 1 6: Changing BlueSMiRF baud rate to Roomba- compatible 57,600 8N1 Chapter 4 — Building a Roomba Bluetooth Interface The BlueSMiRF has many other AT commands besides the... RoombaComm, read the release notes to see if the hwhandshake situation has changed The hwhandshake option is discussed further in the section “RXTX Serial Port Library.” 83 84 Part I — Interfacing Making RoombaComm RoombaComm is a Java API library you’ll be creating to talk to Roombas It will contain a large number of functions to make talking to the Roomba easy It will also have a bunch of higher-level... roombacomm-latest.zip roombahacking.com % cd roombacomm % emacs roombacomm/Drive.java % /makeit.sh % /runit.sh roombacomm.Drive // downloaded from // // // // get into the directory edit the file build it run it The scripts will work on any Unix-like system (Mac OS X, Linux, Windows with Cygwin) For vanilla Windows, you can use makeit.bat and runit.bat, which work the same way Command-Line Roomba Driving . 72 Part I — Interfacing F IGURE 4- 4 : Parts needed for this project Step 1: Preparing the Cable The Mini DIN 8-pin cable preparation is exactly the same as for the serial tether. Cut the cable about. Figure 4- 7 shows the Bluetooth adapter almost com- plete. To make it more manageable and to give the cable some strain-relief in case it is pulled, hot glue it to the edge of the board. For an extra. the Bluetooth Preferences dialog box, turn on Bluetooth, and click Set Up a New Device. You’ll see a screen similar to the one shown in Figure 4- 1 1, asking to choose the device type. These are the