Embedded XINU and WRT 54 GL 12132021 1

Embedded XINU and WRT 54 GL 12/13/2021 1

Topics n Logic and shift operators n Data-driven vs function-driven n Embedded XINU and WRT 54 GL 12/13/2021 2

Shift Operators n << left shift n >> right shift Usage: unsigned int x = 70707; //x = 000000010100 0011 unsigned int y, z; y = x << 2; // y = 00000100 01010000 1100 z = x >> 2; //z = 00000000 01000101 00001100 12/13/2021 3

Logic Operators Bitwise & (AND) Bitwise inclusive | (OR) Bitwise exclusive ^ (XOR) Bitwise negation ~ Usage: unsigned exp 1 = 1; unsigned exp 2 = 4; printf (“ %dn”, exp 1 | exp 2); printf (“ %dn”, exp 1 & exp 2); printf (“ %dn”, exp 1 ^ exp 2); printf (“ %dn”, ~exp 1); n n 12/13/2021 4

Relevance of shift and logic operators n Bitwise operations are necessary for much low-level programming, such as writing device drivers, low-level graphics, communications protocol packet assembly and decoding. n 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) 12/13/2021 5

Data-driven vs function-driven n Lets solve the number game using bitwise operators and functions. n This will give us a general solution than the data-driven one. 12/13/2021 6

Embedded XINU n http: //xinu. mscs. mu. edu/Main_Page n XINU ("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 1980 s. n 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. 12/13/2021 7

Linksys WRT 54 GL n Linux kernel 2. 4 n Based on Broadcom BCM 535 E So. C (System on Chip) n All-in-one Internet-sharing router, n n n 12/13/2021 4 -port switch 54 Mbps wireless-G (802. 11 g) access point Shares a single internet connection with Ethernet wired and wireless-G –B devices Push button setup High security: TKIP and AES encryption providing a powerful firewall 8

WRT 54 GL Block diagram n See attached n Also follow this model: CPU Input 12/13/2021 Storage Output 9

Processor Architecture n WRT 54 Gl uses Broadcom MIPS (Microprocessor without Interlocked Pipelines Stages) processor, common to embedded devices and game consoles. n Model: BCM 5352 n Based on Reduced Instruction Set Architecture (RISC) n The BCM 5532 family of processors is a next generation So. C architecture that combines the CPU, Wireless MAC (media access controller), Ethernet MAC onto one chip 12/13/2021 10

Storage n On board storage is indeed a limitation when using WRT 54 GL in situation other than for which it is meant for. n WRT 54 GL has a flash memory (4 MB), a form of non-volatile storage commonly used in small devices, such as digital camera. n It also use SDRAM (Synchronous Dynamic Random Access Memory) soldered directly into the printed board. DIMM (Dual In-line Memory Module) 12/13/2021 11

Wireless and Ethernet networking n WRT 54 GL has a powerful networking architecture n It provides 5 port Ethernet switch that is broken down into two virtual n n n LANs VLAN 0 and VLAN 1 (default) Wireless interface is bridged by default to the Ethernet switch. Wi. Fi component is BCM 2050, a 802. 11 b/g radio chipset. It uses a diversity chip to balance signals between two built-in antenna. Wi. Fi radio connects to the CPU Wireless MAC on eth 1 which is bridged to VLAN 0 via br 0 interface. Ethernet switch controls Ethernet. LAN and Internet lights, whereas Power, DMZ, WLAN are controlled by GPIO port on the CPU WAN port: plug in cable modem into this port, n n n 12/13/2021 it will pull a DHCP (Dynamic Host Configuration Protocol) address from your ISP (Internet Service Provider). Since it belongs to VLAN 1 it is separate from VLAN 0 and the two are linked by WRT 54 Gl’s routing capabilities. Firewall prevents traffic from flowing from WAN to LAN network, traffic initiated by LAN to exit via WAN. 12

Embedded XINU n http: //xinu. mscs. mu. edu/Memory n ls xinu_mips-1. 0 AUTHORS README include loader system tty LICENSE compile lib shell test uart n See attached XINU directory structure and class diagram 12/13/2021 13

Summary n We discuss important features of WRT 54 GL n We also discussed the structure of Embedded XINU 12/13/2021 14