CS Department Lab-Cams Embedded Systems in Practice

1
CS Department Lab-CamsEmbedded Systems in
Practice

• Implemented by
• The Embedded Systems Group

2
Components of the system

• Dedicated labcam web-server - erson
• Intel Embedded Development board connected to the
  Net - isky
• Intel 8051 micro-processor which is used to
  control the stepper motors on the cameras
• 2 Digital Cameras purchased from Digikey
• ChillCam S/W that takes pictures

3
Steps in the viewing process

• User clicks on labcam link and is transferred to
  erson.
• User has the option to either view activity in
  B256 or B265 and the appropriate page is
  displayed after clicking on the link.
• The picture of the lab taken with the aid of
  ChillCam software is now displayed

4
Steps in moving Camera

• Clicking on the left/right button runs a
  cgi-script (a client networking program) on the
  web server.
• The client program contacts a server program
  running on isky and indicates the users desired
  movement of the camera
• The server communicates this information to the
  8051 which then moves the camera.

5
Web Server/Web Page Design Details

• Since we wanted to be able to control the stepper
  motor through the Net, we had to create a CGI
  program to accomplish this task.
• CGI programs introduce security concerns, and
  hence we were unable to obtain permission to run
  our CGI on the main web-server. This necessitated
  setting up our own dedicated web server to handle
  anything related to the digital cameras.
• It was necessary to decide which language we
  wanted to use to implement the client
  application. Since we were familiar with Berkeley
  sockets programming using C, this became the
  language of choice.
• The following encoding scheme was used to
  indicate the desired camera and motion
• a gt Move camera in B256 right
• b gt Move camera in B256 left
• c gt Move camera in B265 right
• d gt Move camera in B265 left

6
The HTML Code for the B256 Labcam page
ltFONT COLOR"0000FF"gt ltH1 ALIGNCENTERgtThe
Fabulous B256 Cam!lt/H1gt lt/FONTgt ltCENTERgt ltIMG
SRC"/cgi-bin/send_image.pl?imageimg2.jpg"
ALIGNCENTER BORDER5gt lt/CENTERgt ltTABLE
BORDER0 CELLSPACING0 CELLPADDING0 WIDTH"100"
NOSAVE ALIGNCENTERgt ltTR NOSAVEgt ltTD NOSAVE
ALIGNCENTERgt ltFORM method"post"
action"../cgi-bin/client.cgi?b"gt ltinput
type"Submit" value"ltlt"gt lt/formgt lt/TDgt ltTD
NOSAVE ALIGNCENTERgt ltBgtCamera
Controlslt/Bgt lt/TDgt ltTD NOSAVE
ALIGNCENTERgt ltFORM method"post"
action"../cgi-bin/client.cgi?a"gt ltinput
type"submit" value"gtgt"gt lt/formgt lt/TDgt lt/TABLE
gt
7
Client networking application Design Details

• Erson is an Apache web-server running under
  Linux. Hence the client application had to be
  written for the Unix environment
• We had a variety of communications methods to
  pick from serial, firewire, ethernet,
  token-ring, etc. Ethernet became the chosen
  medium due to its prevalence and the fact that we
  were able to install an ethernet card on the
  development board. A variety of protocols could
  have been used, but we selected TCP/IP as the
  means of communications since it is supported in
  linux and we were familiar with writing
  networking applications using TCP/IP.
• Thus the client program utilizes Berkeley socket
  programming to transmit the CGI argument passed
  to it to isky. The program uses TCP as opposed to
  UDP to insure that the data is transmitted. Due
  to the robustness of TCP, the command (a single
  character encoding the camera and desired
  direction of motion) is simply sent to the
  server. The application does not due any of its
  own error checking and hence a packet format is
  not necessary.

8
Portions of Code for Client Net App. (client.cc)
if(strcmp(argv1, "d") 0) //First, open
up a dialogue with isky fd connectTCP(host,
port) // NOTE how we must output a web
page this is required // of any CGI script.
if(fd -1) //We can't talk with
isky! coutltlt"Content-Type
text/html"ltltendlltltendl coutltlt"ltHTMLgt"ltltend
l coutltlt"ltHEADgtltTITLEgtError!lt/TITLEgtlt/HEAD
gt"ltltendl coutltlt"ltBODYgt"ltltendl
coutltlt"ltH1gtError!lt/H1gt"ltltendl
coutltlt"ltPgtServer is busy."ltltendl
coutltlt"Please try again a little later."ltltendl
coutltlt"lt/BODYgt"ltltendl
coutltlt"lt/HTMLgt"ltltendl return 0
//We have a connection write(fd, "d",
1) //We're done talking to isky
close(fd)
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Client.cc continued
// Now that we've successfully moved the camera,
we will output the // correct page. if
(strcmp(argv1, "a") 0 strcmp(argv1,
"b") 0) // MUCH CODE REMOVED
coutltlt"Content-Type text/html"ltltendlltltendl
coutltlt"ltHTMLgt"ltltendl coutltlt"ltHEADgtltTITLEgtThe
Fabulous B256 Cam!lt/TITLEgt"ltltendl coutltlt"ltIMG
SRC\"../cgi-bin/send_image.pl?imageimg2.jpg\"
ALIGNCENTER BORDER5gt"ltltendl
coutltlt"lt/CENTERgt"ltltendl coutltlt"ltTABLE BORDER0
CELLSPACING0 CELLPADDING0 WIDTH\"100\" NOSAVE
ALIGNCENTERgt"ltltendl coutltlt"ltTR
NOSAVEgt"ltltendl coutltlt"ltTD NOSAVE
ALIGNCENTERgt"ltltendl coutltlt"ltFORM
method\"post\" action\"../cgi-bin/client.cgi?b\"
gt"ltltendl coutltlt"ltinput type\"Submit\"
value\"ltlt\"gt"ltltendl coutltlt"lt/formgt"ltltendl
return 0
10
Server Net Application Design Details

• The drivers for the digital cameras were written
  for Windows 95, and since we werent interested
  in writing our own device drivers (not worth the
  effort given our actual goal), we decided to use
  Windows 95. We also used an Embedded Development
  Board donated by Intel to assess its usefulness
  in actual embedded applications. It allowed us to
  hook up an ethernet card for communications as
  well as the parallel port required for
  communication with the digital camera itself.
• Since we had to use Windows 95 on the Intel
  Embedded Development Board, it was necessary to
  implement the server application in the windows
  environment.
• We decided to implement the server using windows
  sockets in C since we were familiar with
  programming in this paradigm. It would have been
  possible to implement the server in a variety of
  other languages Java, Perl, even C in windows
  using MFC.
• The server constantly listened for
  communication from the client application. Once
  the command has been received from the client, it
  is communicated to the 8051 microprocessor using
  serial transmission.
• Serial transmission under windows is performed by
  opening a file for the specific COM Port, and
  associating that file handle with a COM Port
  state. Serial transmission can then be
  facilitated by simply writing to the handle
  representing the COM Port, like any normal file.

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Server Application code (server.cpp)
bool PerformCommand(char cmd, Port p) // make
the new move if (cmd 'a') if (currPos1 lt
POS_LIMIT) currPos1 if
(p.Write(move_command, 1) false ) return
false return true int main() // MUCH
CODE deleted for clarity while( 1 ) //
accept incomingSocket accept(s, 0, 0) if(
incomingSocket ! INVALID_SOCKET )
if( recv(incomingSocket, buf, 1, 0) ! 0 )
MessageBeep(-1) if( PerformCommand(buf0
, p) false ) cout ltlt "unable
to execute user's command." ltlt endl closeso
cket(incomingSocket)
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Server Application code (port.cpp)
PortPort(unsigned port, unsigned baud)
DefaultTimeout(1000) char buf32 DCB
commState sprintf(buf, "COMi", port)
if( (handle CreateFile(buf,
GENERIC_READ GENERIC_WRITE,
0,
0, OPEN_EXISTING,
FILE_FLAG_OVERLAPPED,
0))
INVALID_HANDLE_VALUE ) handle 0
else GetCommState(handle,
commState) commState.BaudRate baud
commState.Parity NOPARITY
unsigned PortWrite(const void buf,
unsigned szBuf) DWORD check 0 if(
handle ) WriteFile(handle, buf, szBuf,
check, 0) return check
13
Stepper Motor Circuit Details

• We decided to use a stepper motor to allow the
  movement of the camera since we wanted the
  movement to occur in steps instead of
  continuously (as in DC motors).
• We decided to use an 8051 microprocessor to
  control the stepper motor due to the cheap cost
  of the processor and ease of use (possible to
  program it in C using the Keil compiler). It is
  always possible to design a custom circuit to
  accomplish any given task, but this makes the
  task quite difficult and time consuming (even
  expensive in this case).
• Furthermore, it would have been possible to
  control the stepper motor directly, however we
  used an ASIC to control the clockwise and
  counter-clockwise motion of the stepper motor
  (the MC3479P chip). This is because it is much
  easier to control the IC than the motor itself,
  and furthermore a hardware solution is generally
  much faster than a software implementation. You
  are already familiar with the details of
  controlling a stepper motor using this chip from
  your stepper motor lab.
• Similarly, you are familiar with the exact
  methods used to perform serial communication
  using the 8051 from your lab exercise on this
  subject (utilizing the LT1130CN chip to perform a
  conversion from RS232 to TTL voltage levels).

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Stepper Motor Circuit Details Continued

• We decided that it would be possible to control
  both of the cameras using a single 8051, and
  hence settled on the communication scheme between
  the Intel development board and the 8051
  described earlier (ie a, b,. c, and d
  representing both a particular camera and a
  specified movement direction). We could just as
  easily have used 2 microprocessors to accomplish
  the task, but this would obviously have been a
  waste of resources.
• Thus controlling the movement of the digital
  camera simply involves the combination of the
  principles learned in 2 of your labs (once the
  server, isky, is aware of the users desired
  camera movement)

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8051 microprocessor code
sbit CommonDirection P20 sbit B256Clk
P21 sbit B265Clk P22 define CLOCKWISE
0 define COUNTER_CLOCKWISE 1 define B256_RIGHT
'a' define B256_LEFT 'b' define B265_RIGHT
'c' define B265_LEFT 'd' void main()
for() switch(ReceiveSerial())
case B256_LEFT CommonDirection
CLOCKWISE B256Clk 1 Delay(250) B256Clk
0 break case B256_RIGHT
CommonDirection COUNTER_CLOCKWISE B256Cl
k 1 Delay(250) B256Clk 0 break