Embedded XINU and WRT54GLTopicsShift OperatorsLogic OperatorsRelevance of shift and logic operatorsWRT54GLHistoryCommon FeaturesCommon Features (Contd.)Linksys WRT54GL (contd.)Processor ArchitectureBCM5352WRT54GL Block diagramSlide 14StorageWireless and Ethernet networkingWhat does WRT54GL do?The Basic Hardware modificationsThe NSF-Supported Facility at UBEmbedded XINUSlide 2101/14/191Embedded XINU and WRT54GL01/14/192TopicsLogic and shift operatorsOptimizing operations (mul, div VS shiftL, shiftR)WRT54GL architecture and internalsEmbedded XINU01/14/193Shift Operators<< left shift>> right shiftUsage:unsigned int x = 70707;//x = 00000000 00000001 00010100 00110011unsigned int y, z;y = x << 2;// y = 00000000 00000100 01010000 11001100z = x >> 2;//z = 00000000 00000000 01000101 0000110001/14/194Logic OperatorsBitwise & (AND)Bitwise inclusive | (OR)Bitwise exclusive ^ (XOR)Bitwise negation ~Usage:unsigned exp1 = 1;unsigned exp2 = 4;printf (“ %d\n”, exp1 | exp2); printf (“ %d\n”, exp1 & exp2);printf (“ %d\n”, exp1 ^ exp2);printf (“ %d\n”, ~exp1);01/14/195Relevance of shift and logic operatorsBitwise operations are necessary for much low-level programming, such as writing device drivers, low-level graphics, communications protocol packet assembly and decoding.Device drivers use these operators to test the presence or absence of a bit in a serial port or a device input. (checking for on or off)WRT54GLHistory of WRT54G Open source firmware Common featuresProcessor architecture (BCM5352)WRT54GL Block diagramHistoryIntroduced in 2002In 2003 Andrew Miklas posted to Linux Kernel Mailing List about Linksys using GPL code in its firmwareLinksys executives gave into the pressure from the community, Linksys released the code to the community under GPL.Common FeaturesPower: 12VDC 1.0ampThis power requirement is standard for embedded devices and wireless access pointsThis makes them compatible with Power over Ethernet (PoE)This especially significant in mobile environment.The Reset button: to reset the configurationCommon Features (Contd.)LED lights to indicate various conditionsPower : indicates presence of powerDMZ: use differs; ex: can show boot progressWLAN LED Ethernet InternetYou can manipulate the LED thru’ your code by changing contents of system files.01/14/1910Linksys WRT54GL (contd.)Linux kernel 2.4Based on Broadcom BCM535E SoC (System on Chip)All-in-one Internet-sharing router,4-port switch54Mbps wireless-G (802.11g) access pointShares a single internet connection with Ethernet wired and wireless-G –B devicesPush button setupHigh security: TKIP and AES encryption providing a powerful firewallProcessor ArchitectureProcessor: Broadcom MIPS (Microprocessor without Interlocked Pipeline Stages) processor, common to embedded devices and game consoles.RISC (reduced instruction set computer)MIPS is used Sony playstation for example.We will develop programs in Linux OS: you will use Timberlake for off-campus; you can also a special server we have for the course nexos-dlink.cse.buffalo.eduWe will cross compile and load the firmware into WRT54GL (“port”)BCM5352Next generation SoC (System on a Chip)SoC: combines CPU + Wireless MAC + Ethernet MAC onto one chipFlash memorySDRAMWireless access (802.11)Ethernet switch01/14/1913WRT54GL Block diagramSee attached Also follow this model:CPUStorageInput Output01/14/1914Processor ArchitectureWRT54Gl uses Broadcom MIPS (Microprocessor without Interlocked Pipelines Stages) processor, common to embedded devices and game consoles.Model: BCM5352Based on Reduced Instruction Set Architecture (RISC)The BCM5532 family of processors is a next generation SoC architecture that combines the CPU, Wireless MAC (media access controller), Ethernet MAC onto one chip01/14/1915StorageOn board storage is indeed a limitation when using WRT54GL in situation other than for which it is meant for.WRT54GL has a flash memory (4 MB), a form of non-volatile storage commonly used in small devices, such as digital camera.It also use SDRAM (Synchronous Dynamic Random Access Memory) soldered directly into the printed board. DIMM (Dual In-line Memory Module)01/14/1916Wireless and Ethernet networkingWRT54GL has a powerful networking architectureIt provides 5 port Ethernet switch that is broken down into two virtual LANs VLAN0 and VLAN1 (default)Wireless interface is bridged by default to the Ethernet switch.WiFi component is BCM2050, a 802.11b/g radio chipset.It uses a diversity chip to balance signals between two built-in antenna.WiFi radio connects to the CPU Wireless MAC on eth1 which is bridged to VLAN0 via br0 interface.Ethernet switch controls EthernetLAN and Internet lights, whereas Power, DMZ, WLAN are controlled by GPIO port on the CPUWAN port: plug in cable modem into this port, it will pull a DHCP (Dynamic Host Configuration Protocol) address from your ISP (Internet Service Provider). Since it belongs to VLAN1 it is separate from VLAN0 and the two are linked by WRT54Gl’s routing capabilities.Firewall prevents traffic from flowing from WAN to LAN network, traffic initiated by LAN to exit via WAN.What does WRT54GL do?Creates a network between the wireless interface and the LAN ports known as br0.Router address is 192.168.1.1 by default.WLAN port (port 4).Typically you will plug your cable modem into this port; this will pull the DHCP address from your ISP. WAN and LAN are separate network linked by WRT54GLThe Basic Hardware modifications01/14/1918SIGCSE 2009 NSF SHOWCASEThe NSF-Supported Facility at UB01/14/1919SIGCSE 2009 NSF SHOWCASE01/14/1920Embedded XINUhttp://xinu.mscs.mu.edu/Main_PageXINU ("XINU Is Not Unix", a recursive acronym) is a Unix-like operating system originally developed by Douglas Comer for instructional purposes at Purdue University in the 1980s.Embedded XINU is a reimplementation of the original XINU operating system on the MIPS processor which is able to run on inexpensive wireless routers and is suitable for courses and research in the areas of Operating Systems, Hardware Systems, Embedded Systems, and Compilers.01/14/1921Embedded XINUhttp://xinu.mscs.mu.edu/Memoryls xinu_mips-1.0AUTHORS README include loader system ttyLICENSE compile lib shell test uartSee attached XINU
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