Hacking Roomba - Tod E.Kurt Part 12 potx

312 Part III — More Complex Interfacing F IGURE 14-7: Disabling the WAN port in OpenWrt 5. Enable Wireless client mode. ■ Select the Wireless sub-category. Second to the IP address, this is the most impor- tant configuration page. Normally you configure OpenWrt to act as an access point. Instead it will be a client on your existing wireless network like any other client. ■ In the ESSID text box, type the name of your wireless network. ■ In the Mode pop-up menu, change Access Point to Client (Bridge). ■ Leave Channel at Auto and leave ESSID Broadcast at Hide. ■ If you use encryption on your network, adjust the encryption settings appropri- ately. Figure 14-8 shows the settings for connecting to an unencrypted Wi-Fi network named todbot. ■ Press Save Changes when done. 313 Chapter 14 — Putting Linux on Roomba F IGURE 14-8: Configuring OpenWrt as a wireless client 6. Apply changes. ■ At this point you have all the changes queued up and you can review them with Review Changes. ■ Or, just press Apply Changes and you’ll see OpenWrt reconfiguring itself. Then, because you changed its IP address, you won’t be able to contact it. It will have joined your wireless network, so you can connect to it wirelessly now. 7. Change your PC’s network configuration to be back on your wireless net. Use your browser to go to the new IP address of the WL-HDD. You should again see your router’s home status page like in Figure 14-4. The WL-HDD is now fully configured network-wise and it’s time for some fun. 314 Part III — More Complex Interfacing Playing Around on Your Embedded Linux System Just like any good Linux system, OpenWrt has an SSH server. You can log into it like any other Linux box: % ssh root@192.168.0.100 root@192.168.0.100’s password: BusyBox v1.00 (2006.03.27-00:00+0000) Built-in shell (ash) Enter ‘help’ for a list of built-in commands. _______ ________ __ | |. — — — — — — | | | |. — — .| |_ | - || _ | -__| || | | || _|| _| |_______|| __|_____|__|__||________||__| |____| |__| W I R E L E S S F R E E D O M WHITE RUSSIAN (RC5) ———————————————- * 2 oz Vodka Mix the Vodka and Kahlua together * 1 oz Kahlua over ice, then float the cream or * 1/2oz cream milk on the top. —————————————————————————- root@OpenWrt:~# Of course, unlike a normal Linux system, the disk space situation is very different: root@OpenWrt:~# df -h Filesystem Size Used Available Use% Mounted on /dev/root 3.2M 1.8M 1.4M 57% / none 7.0M 20.0k 7.0M 0% /tmp Notice you only have 3.2 MB of disk total, and over half of it is already in use. But otherwise, it’s very much like any other command line Linux system. You can ping Google: root@OpenWrt:~# ping google.com PING google.com (64.233.167.99): 56 data bytes 64 bytes from 64.233.167.99: icmp_seq=0 ttl=246 time=82.1 ms 64 bytes from 64.233.167.99: icmp_seq=1 ttl=246 time=84.7 ms 64 bytes from 64.233.167.99: icmp_seq=2 ttl=246 time=83.5 ms Inspecting the Running System As with any Linux system, you have access to a variety of command line tools to inspect the running system. You can run top to see what processes are running. Mem: 8116K used, 6232K free, 0K shrd, 0K buff, 3140K cached Load average: 0.00, 0.00, 0.00 (State: S=sleeping R=running, i W=waiting) PID USER STATUS RSS PPID %CPU %MEM COMMAND 2201 root R 388 2196 0.9 2.7 top 2195 root S 600 296 0.5 4.1 dropbear 2196 root S 436 2195 0.0 3.0 ash 296 root S 400 1 0.0 2.7 dropbear 299 root S 380 1 0.0 2.6 httpd 291 nobody S 364 1 0.0 2.5 dnsmasq 315 Chapter 14 — Putting Linux on Roomba 1 root S 360 0 0.0 2.5 init 62 root S 344 1 0.0 2.3 syslogd 309 root S 344 1 0.0 2.3 crond 2149 root S 332 1 0.0 2.3 wifi 64 root S 304 1 0.0 2.1 klogd 301 root S 260 1 0.0 1.8 telnetd And you can run other common Linux programs like netstat, ifconfig, and ps. If you’re familiar with Linux, you’ll find most of the low-level administration and inspection tasks available to you. For example, the entire /proc virtual file system exists to give you visibility into the running Linux kernel. Even writing little shell scripts on the command line is possible: root@OpenWrt:~# while [ 1 ] ; do > echo “OpenWrt is the best!” > sleep 1 > done OpenWrt is the best! OpenWrt is the best! OpenWrt is the best! The ipkg Packaging System You’ve no doubt noticed the clock is wrong. The easiest way to fix that is to get an NTP client from the ipkg repository. Ipkg is a code packaging and installation technology, a package repository, and a command line program. It takes away a lot of the drudgery of installing new software. Listing 14-1 shows a typical interaction with the ipkg command. If you’re familiar with other network-based packaging systems like ports, yum, or apt-get, using ipkg will be immediately familiar to you. Listing 14-1: Using ipkg to Find and Install ntpclient root@OpenWrt:~# ipkg update Downloading http://downloads.openwrt.org/whiterussian/packages/Packages Updated list of available packages in /usr/lib/ipkg/lists/ i whiterussian Downloading http://downloads.openwrt.org/whiterussian/ i packages/non-free/Packages Updated list of available packages in /usr/lib/ipkg/lists/ i non-free Successfully terminated. root@OpenWrt:~# ipkg list | grep ntp ntpclient - 2003_194-2 - NTP client for setting system time from NTP servers. openntpd - 3.7p1-1 - OpenNTPD is a FREE, easy to use implementation of NTP Continued 316 Part III — More Complex Interfacing Listing 14-1 Continued root@OpenWrt:~# ipkg install ntpclient Installing ntpclient (2003_194-2) to root Downloading http://downloads.openwrt.org/whiterussian/packages/ntpclient_ i 2003_194-2_mipsel.ipk Configuring ntpclient ntSuccessfully terminated. root@OpenWrt:~# date Sat Jan 1 00:29:08 UTC 2000 root@OpenWrt:~# ntpclient -c 1 -s -h pool.ntp.org 38914 01341.848 19061.0 2251.5 9917.4 50613.4 0 root@OpenWrt:~# date Mon Jul 17 23:21:59 UTC 2006 Reverting to Factory Firmware In the event you run into some problems with OpenWrt or if you want to sell the WL-HDD, you can always re-flash with the factory firmware. The steps are almost exactly the same as flashing OpenWrt: 1. Go to http://support.asus.com/ and find the latest firmware file for the WL- HDD. You will download a ZIP file and inside it will be a file named something like WLHDD_1.2.3.9_en.trx. Notice how the .trx extension is the same as the OpenWrt firmware you flashed. 2. Use the method above with flash-wd-hdd.sh to reflash the WL-HDD. There is a utility program for Windows on the ASUS site that also supposedly will help you reflash. Also, inside of OpenWrt, there is a Firmware Upgrade page under the System category. There have been no reported cases of irreparably bricking an ASUS wireless router by using OpenWrt, so you shouldn’t be reluctant to try it. Controlling Roomba in OpenWrt Now that you have a working tiny Linux system, it’s time to figure out how to get it to talk to the Roomba. As mentioned earlier, most of the chips OpenWrt supports have one or two built-in serial ports (UARTs) that you could solder to if you opened up the box. The WL-HDD doesn’t appear to have one of those chips. That’s okay, because not only does the WL-HDD have a USB port, but OpenWrt has several USB serial drivers. 317 Chapter 14 — Putting Linux on Roomba USB Serial Port Drivers The Linux USB serial device drivers that have been packaged for OpenWrt are: ftdi_sio, pl2303, belkin_sa, and mct_u232. These four drivers enable you to communicate with 90 percent of the USB-to-serial adapters out there and all of the generic ones. Figure 14-9 shows a common generic USB-to-serial adapter. The actual chip for the adapter is embedded in the hood of the RS-232 connector. These are available from various online retailers like NewEgg.com for around $9. There’s no indication as to which chip one uses; you have to plug it in to find out. But for only $9 it’s a pretty cheap experiment, and if it isn’t supported you can probably use it on a fully-fledged PC. The Keyspan adapter you’ve used in the previous chapters doesn’t use any of these drivers. There does exist an open-source Linux driver for the Keyspan adapter. It just hasn’t been packaged for OpenWrt yet. There’s no reason to think that it wouldn’t work. Most users of USB serial on OpenWrt are connecting to GPS devices and PDAs, both of which tend to use the same USB-to-serial chips as the generic adapters. The RooStick uses the Silicon Labas CP2103 chip, which appears to work with the standard Linux cp2101 driver. Unfortunately that’s another driver that hasn’t been packaged for use with OpenWrt yet. There’s no reason to think it couldn’t be and it may be part of the next OpenWrt distribution. On the positive side, the Arduino board uses an FTDI chip that is supported by the ftdi_sio driver. This means you could program an Arduino board to do something based on serial com- mands and then plug the board into the WL-HDD. This is very powerful. It’s so easy to add sensors and actuators to Arduino that Arduino could become a sort of I/O co-processor for the WL-HDD. There have been sporadic reports of problems with combinations of some WL-HDDs with certain USB-to-serial adapters. If you have problems with one serial adapter, try another. If you think the problem is due to the WL-HDD, try the Linksys WRTSL54GS discussed in Chapter 15. It’s almost twice as expensive but has a more advanced USB interface with fewer reported problems. This is the disadvantage of hacking consumer electronics: there’s no guarantee the vendor will keep the device the same. Installing USB Serial Port Drivers in OpenWrt Thanks to ipkg, installing new kernel modules is a snap. Kernel modules are packaged up just like normal programs. The two kernel module packages needed to get serial working are: Ⅲ kmod-usb-ohci: Contains the drivers usbcore and usb-ohci needed to talk to the USB interface. Ⅲ kmod-usb-serial: Contains the general driver usbserial and the device-specific drivers ftdi_sio, pl2303, belkin_sa, and mct_u232. 318 Part III — More Complex Interfacing F IGURE 14-9: Generic USB-to-serial adapter, uses PL2303 chip Listing 14-2 shows how to use ipkg to install the drivers and insmod to load the drivers. To determine if these drivers loaded successfully, the best way is to check the output of dmesg and look for appropriate status or error messages. The last part of Listing 14-2 shows what you should expect to see. The most important line is the last one, which tells you which device file the driver has created for you to use. In the example, the device is /dev/usb/tts/0. OpenWrt uses the new devFS naming scheme for device files, instead of the more familiar /dev/ttyUSB0. Listing 14-2: Installing Serial Port Drivers in OpenWrt root@OpenWrt:~# ipkg install kmod-usb-ohci kmod-usb-serial Installing kmod-usb-ohci (2.4.30-brcm-3) to root Downloading http://downloads.openwrt.org/whiterussian/packages/ i kmod-usb-ohci_2.4.30-brcm-3_mipsel.ipk Installing kmod-usb-serial (2.4.30-brcm-3) to root Downloading http://downloads.openwrt.org/whiterussian/packages/ i 319 Chapter 14 — Putting Linux on Roomba Listing 14-2 Continued kmod-usb-serial_2.4.30-brcm-3_mipsel.ipk Configuring kmod-usb-ohci Configuring kmod-usb-serial Successfully terminated. root@OpenWrt:~# insmod usbcore Using /lib/modules/2.4.30/usbcore.o root@OpenWrt:~# insmod usb-ohci Using /lib/modules/2.4.30/usb-ohci.o root@OpenWrt:~# insmod usbserial Using /lib/modules/2.4.30/usbserial.o root@OpenWrt:~# insmod pl2303 Using /lib/modules/2.4.30/pl2303.o root@OpenWrt:~# dmesg [ ] usb.c: registered new driver usbdevfs usb.c: registered new driver hub PCI: Setting latency timer of device 00:04.0 to 64 usb-ohci.c: USB OHCI at membase 0xb8004000, IRQ 2 usb-ohci.c: usb-00:04.0, PCI device 14e4:4715 usb.c: new USB bus registered, assigned bus number 1 hub.c: USB hub found hub.c: 2 ports detected usb.c: registered new driver serial usbserial.c: USB Serial support registered for Generic usbserial.c: USB Serial Driver core v1.4 usbserial.c: USB Serial support registered for PL-2303 hub.c: new USB device 01:02.0-1, assigned address 2 pl2303.c: Prolific PL2303 USB to serial adaptor driver v0.11 usbserial.c: pl2303 converter detected usbserial.c: PL-2303 converter now attached to ttyUSB0 (or usb/tts/0 for devfs) Making the Drivers Load on Reboot Although the drivers are loaded now, they won’t reload on reboot. To have them load automati- cally each time the WL-HDD is rebooted, do the following to add the module names to the /etc/modules file: root@OpenWrt:~# echo “usbcore” >> /etc/modules root@OpenWrt:~# echo “usb-ohci” >> /etc/modules root@OpenWrt:~# echo “usbserial” >> /etc/modules root@OpenWrt:~# echo “pl2303” >> /etc/modules The order of the above lines is important. The usbcore driver must load before usb-ohci, and so on. 320 Part III — More Complex Interfacing Debugging USB Devices If you ever have problems with USB devices on Linux (any Linux, not just OpenWrt), you have options to diagnose them. The first is to look at all the dmesg output you can, as shown in Listing 14-2. The next is to see which kernel modules are currently loaded: root@OpenWrt:~# lsmod Module Size Used by Tainted: P ftdi_sio 21848 0 (unused) usb-ohci 19204 0 (unused) pl2303 12552 0 usbserial 23868 0 [ftdi_sio pl2303] switch-core 4896 0 wlcompat 14896 0 (unused) usbcore 74792 1 [ftdi_sio usb-ohci pl2303 usbserial] wl 423640 0 (unused) diag 3320 0 (unused) If you see something missing (or something that shouldn’t be there), use insmod and rmmod to fix things up. To see which kernel modules are available, look in the /lib/modules/2.4.30/ directory. Each file is a different kernel module. The /proc virtual file system contains huge amounts of interesting data about the running kernel. Use cat /proc/cpuinfo to get details on the processor or cat /proc/pci to see what exists on the internal PCI bus. Similarly for USB, you can see what’s connected on the USB bus by doing as in Listing 14-3. If you understand USB, it gives you a lot of good infor- mation. It’s a bit verbose, however, and if all you really want to know is if something is plugged in, install lsusb and run it. The dmesg program spews many apparent errors. Usually you can ignore these. OpenWrt is still a work in progress, and some parts of the system are a little too chatty for users who aren’t developers. As you become more familiar with OpenWrt, you’ll get to learn which messages are true errors and which are not. As OpenWrt approaches a 1.0 release, the volume of dmesg out- put has been going down. Listing 14-3: Inspecting USB Devices via /proc and lsusb root@OpenWrt:~# cat /proc/bus/usb/devices T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2 B: Alloc= 0/900 us ( 0%), #Int= 0, #Iso= 0 D: Ver= 1.10 Cls=09(hub ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1 P: Vendor=0000 ProdID=0000 Rev= 0.00 S: Product=USB OHCI Root Hub S: SerialNumber=b8004000 C:* #Ifs= 1 Cfg#= 1 Atr=40 MxPwr= 0mA I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub 321 Chapter 14 — Putting Linux on Roomba Listing 14-3 Continued E: Ad=81(I) Atr=03(Int.) MxPS= 2 Ivl=255ms T: Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=12 MxCh= 0 D: Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 P: Vendor=0557 ProdID=2008 Rev= 3.00 S: Manufacturer=Prolific Technology Inc. S: Product=USB-Serial Controller C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA I: If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=serial E: Ad=81(I) Atr=03(Int.) MxPS= 10 Ivl=1ms E: Ad=02(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms E: Ad=83(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms root@OpenWrt:~# ipkg install lsusb [ ] root@OpenWrt:~# lsusb Bus 001 Device 001: ID 0000:0000 Bus 001 Device 004: ID 0557:2008 ATEN International Co., Ltd UC-232A i Serial Port [pl2303] Scripting Language Control Now you have an embedded Linux system with a functioning serial port. It is time to hook it up to Roomba. Since the USB-to-serial adapter has the same RS-232 connector as the serial tether of Chapter 3, just connect it to the adapter and Roomba and you’re good to go. There have been efforts to get Java working in OpenWrt via the SableVM (http:// sablevm.org/) or JamVM (http://jamvm.sourceforge.net/), but getting a working Java VM with the system classes in the remaining space of the WL-HDD would be difficult. There are many alternatives to Java, however, and it would be interesting to try some of them. Shell Script Control Linux supports many ways of dealing with serial ports. Unix-like operating systems treat everything as files, even devices such as serial ports. This level of abstraction enables you to deal with almost any device in any language, all just by opening files. Need to format a disk? Open /dev/hdd. Need to play an audio file? Send your WAV file to /dev/audio. You can even control Roomba from the command line: % printf “\x89\x00\xc8\x80\x00” > /dev/usb/tts/0 # DRIVE straight at 200 mm/s (You use \x89 to send bytes using hexadecimal codes.) [...]... Listing 1 4-5 shows the commands needed to do that, as well as download the roombacmd.mpl script and install everything in a non-volatile location Listing 1 4-5 : Installing and Using roombacmd.mpl root@OpenWrt:~# ipkg install microperl root@OpenWrt:~# ipkg install libgcc root@OpenWrt:~# wget http://roombahacking.com/software/roombacmd/roombacmd.mpl root@OpenWrt:~# wget http://roombahacking.com/software/roombacmd/stty.tar.gz... chmod +x /roombacmd.mpl root@OpenWrt:~# mv stty roombacmd.mpl /usr/bin With everything in place you can now control Roomba from the command line of the WLHDD Listing 1 4-6 shows a simple Logo-like example of drawing a square with the Roomba Listing 1 4-6 : Controlling Roomba from the Command Line root@OpenWrt:~# # draw a square root@OpenWrt:~# /roombacmd.mpl /dev/usb/tts/0 init root@OpenWrt:~# /roombacmd.mpl... OpenWrt is very tolerant of sudden power removal Chapter 14 — Putting Linux on Roomba FIGURE 1 4-1 4: Portable battery-powered Wi-Fi hard drive ready to go To set the WL-HDD up for use with Roomba, gather up the battery pack, USB-to-serial adapter, and Roomba serial tether and place them all in a slightly larger enclosure Figure 1 4-1 5 shows a plastic sandwich holder (grocery store again) holding all three,... N82E1683 3124 057 Ⅲ Creative Instant Webcam, or equivalent, Newegg N82E1683010 6120 Ⅲ USB flash drive, any capacity, Newegg N82E16820211027 Ⅲ USB hub, 4-port travel size, Newegg N82E16817201604 Ⅲ Generic USB-to-serial adapter, or USB dongle (see sidebar below) Ⅲ Power plug, standard barrel connector, Radio Shack part number 27 4-1 569 Ⅲ 9V battery snap connector, Radio Shack part number 27 0-3 25 Ⅲ 8-cell AA... usage() { Chapter 14 — Putting Linux on Roomba Listing 1 4-4 Continued printf “Usage: $0 {serialport} “ “{init|forward|backward|spinleft|spinright|stop}\n”; exit(1); } sub roomba_ init() { # this style stty is for linux system(“stty -F $PORT 57600 raw -parenb -parodd cs8 -hupcl -cstopb clocal”); printf “\x80” > $PORT; sleep 0.2; printf “\x82” > $PORT; sleep 0.2; } sub roomba_ forward() { $vel=”\x00\xc8”;... on the WL-HDD battery pack, with an even better enclosure, see www aximsite.com/boards/showpost.php?p=1105083 329 330 Part III — More Complex Interfacing FIGURE 1 4-1 5: Serial tether, USB-to-serial adapter, and battery pack, sealed for freshness FIGURE 1 4-1 6: Wireless Linux on a Roomba Chapter 14 — Putting Linux on Roomba Summary You now have a wireless embedded Linux system that controls Roomba, all... ‘init’ ) { roomba_ init(); } elsif( $CMD eq ‘forward’ ) { roomba_ forward(); } Continued 323 324 Part III — More Complex Interfacing Listing 1 4-4 Continued elsif( $CMD eq ‘backward’ ) { roomba_ backward(); } elsif( $CMD eq ‘spinleft’ ) { roomba_ spinleft(); } elsif( $CMD eq ‘spinright’ ) { roomba_ spinright(); } elsif( $CMD eq ‘stop’ ) { roomba_ stop(); } else { usage(); } In order to use the roombacmd.mpl... root@OpenWrt:~# wget http://roombahacking.com/software/openwrt/spcacat.gz root@OpenWrt:~# gunzip spcacat.gz root@OpenWrt:~# chmod +x spcacat root@OpenWrt:~# mv spcacat /usr/bin root@OpenWrt:~# ln -s /dev/v4l/video0 /dev/video0 root@OpenWrt:~# spcacat -d /dev/video0 -g -f jpg -p 1000 -o You can run spcacat with no arguments to see what its options are The notable ones being used here are: Ⅲ -f jpg: Data format... spinright ; i /roombacmd.mpl /dev/usb/tts/0 forward ; i /roombacmd.mpl /dev/usb/tts/0 stop Making It All Truly Wireless Until now you’ve been powering the WL-HDD from its AC adapter That’s fine for debugging, but the point is to make the WL-HDD completely stand-alone and mobile on top of the Roomba So the next step is to figure out how to power the WL-HDD Asus products usually ship with a high-quality switching... hours from a fully-charged battery pack That’s about three times longer than Roomba lasts on its battery pack FIGURE 1 4-1 3: Testing current draw of the WL-HDD WL-HDD on the Go If you would like to use the WL-HDD without Roomba, you can easily lash together the battery pack to the WL-HDD and take it anywhere you want Figure 1 4-1 4 shows how you could do it with a long piece of Velcro The resulting bundle . order to configure the device something else is needed. For serial devices, you need to set the baud rate and other parameters, and the standard way of setting those parameters is with the stty. to see. The most important line is the last one, which tells you which device file the driver has created for you to use. In the example, the device is /dev/usb/tts/0. OpenWrt uses the new devFS. USB-to-serial adapters out there and all of the generic ones. Figure 1 4-9 shows a common generic USB-to-serial adapter. The actual chip for the adapter is embedded in the hood of the RS-232 connector.