CCN CCN Central Control Network Winter & Spring 2002/03 Student : Kormas Tal Guide : Gerber Alex

CCN CCN - motivation Many systems around the world use central computer for security devices (such as entrance and security cameras). Most of the devices are low resource requires and so many could be connected to one computer. We would like to take advantage of the USB port speed and availability, and implement multiple area network (a separate bus for each area) connected to it.

CCN CCN – network rates CAN bus : the CAN uses RS485 physical layer, so it’s bit rate is up to 125KB/sec. The connection to the computer is USB, and if we assume we use USB 1.1, we could reach up to 12MB/sec (with more then one CAN bus, of course).

CCN CCN – main idea Each device uses bus interface to connect a CAN bus. Each level/area have it’s own bus. All buses controlled by a master device, which also convert the CAN protocol into USB protocol. All the Can Masters outputs (USB) are connected to a USB Hub (which is power supplied, so the net will keep working when communication to the computer N/A). The hub connected to a memory unit for keeping the data in a FIFO line if the computer is down.

CAN – what is it? CAN is a network layer, which is used in many systems (such as cars) to connect the application layer with the physical layer. CAN uses RS485, RS232 or ISO/IS as it’s physical layer. The use of CAN will give us less time to deal with the network transport layer and more time for the application layer, since there are CAN controllers and master that we could use on the market.

USB HUB תור FIFO עם זכרון CAN BUS CAN to USB & Can Master CCN CCN – block diagram view אלמנט תקשורת ושליטה

CCN CCN – the bus interface we need the bus interface for writing the bus. Although most of the devices are not sending/receiving data most of the time, we would like to have less errors and collision on the bus. This is important, since we want to have a lot of devices on the bus, and so we need to keep it safe enough for data to be transmitted (or we could have only few devices on the bus since they will keep on colliding).

CCN CCN – the FIFO element There are two computers, and they will be synchronized since we want to increase availability. The FIFO line will keep messages in-order, for security (will be explained later). In case both computers are down, the FIFO element will save messages, and so we won’t lose information (i.e. log, security cam).

In-order importance Let’s assume the following line of events: 1)A student enter the building (B). 2)B enters the pcfarm. 3)Other student leaves pcfarm (C). 4)A computer is down. 5)B leaves the pcfarm. And let’s assume there is no other student present.

In-order importance (cont.) If we not save In-order, we could find out: 1)Student B enters the building 2)A computer is down. 3)Student C leaves pcfarm. 4)Student B enters pcfarm. 5)Student B leaves pcfarm. If the computer was stolen, we would receive different conclusion In-Order need to be kept.

CCN CCN – major mile stones הפרוייקט הוא שנתי, ולכן יבוצע ב – 2 שלבים: 1) הקמת רשת עם CAN bus יחיד : 31/01/03 חלק זה כולל בתוכו כתיבת תוכנה לניהול בסיסי של הרשת. 2) הקמת רשת עם CAN bus נוסף וחיבור דרךHUB עד : 31/03/03. 3) שיפור התוכנה והכנת רכיב זיכרון לשמירת המידע (כנוסף לשלב 2).

CCN – part 1 timetable הזמנת רכיבים : עד קבלת הרכיבים, הכרתם והכרת אופן השימוש בהם: עד חיבור מחשב ל CAN דרך USB: עד הקמת רשת בסיסית (Master-Slave) : עד הקמת רשת : מחשב עם הרשת הבסיסית : עד