Difference between revisions of "Line Following Sensor"

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This page describes the connection of the i2c line following sensor to the Boe-Bot robot.
 
This page describes the connection of the i2c line following sensor to the Boe-Bot robot.
  
 +
[[Image:LineSensorI2Cphoto.jpg]]
  
 
* [http://www.roboticsconnection.com/p-67-line-following-sensor.aspx I2C Line Following Sensor] by the [http://www.roboticsconnection.com Robotics Connection Inc.]
 
* [http://www.roboticsconnection.com/p-67-line-following-sensor.aspx I2C Line Following Sensor] by the [http://www.roboticsconnection.com Robotics Connection Inc.]
 +
 +
This sensor uses an i2c bus for connection with the processor. To understand more about the
 +
communication, read following two articles:
  
 
* Jon Williams: [http://www.parallax.com/dl/docs/cols/nv/vol3/col/nv85.pdf I2C Fun For Everyone]
 
* Jon Williams: [http://www.parallax.com/dl/docs/cols/nv/vol3/col/nv85.pdf I2C Fun For Everyone]
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* Jon Williams: [http://www.parallax.com/dl/docs/cols/nv/vol5/col/nv115.pdf I2C Again – And the Case for Continuos
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* Jon Williams: [http://www.parallax.com/dl/docs/cols/nv/vol5/col/nv115.pdf I2C Again – And the Case for Continuos Improvement]
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Improvement]
+
 
 +
 
 +
Please, read the [http://www.roboticsconnection.com/userForums/Topic944-10-1.aspx following communication] in case of the problems with line detection. And there is a [http://www.roboticsconnection.com/userForums/Topic1217-10-1.aspx solution]: sensors used to be separated from themselves.
 +
 
 +
 
  
  
 
The connection diagram:
 
The connection diagram:
  
−
[[Image:LineSensorConnection.png]]
+
[[Image:LineSensorConnection.png|300px]]
  
 
The photo of the connection:
 
The photo of the connection:
  
−
[[Image:LineSensorPhoto.jpg]]
+
[[Image:LineSensorPhoto.jpg|300px]]
  
 
The demonstration software:
 
The demonstration software:
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'  {$STAMP BS2}
 
'  {$STAMP BS2}
 
'  {$PBASIC 2.5}
 
'  {$PBASIC 2.5}
−
'
 
−
' =========================================================================
 
−
 
−
 
−
' -----[ Program Description ]---------------------------------------------
 
−
'
 
−
' Generic I2C code for non-BS2p/BS2pe modules.
 
−
 
−
 
−
' -----[ Revision History ]------------------------------------------------
 
−
'
 
−
' 18 AUG 2004 - Updated and made routines completely generic
 
−
 
  
 
' -----[ I/O Definitions ]-------------------------------------------------
 
' -----[ I/O Definitions ]-------------------------------------------------
−
 
 
SDA            PIN    0                      ' I2C serial data line
 
SDA            PIN    0                      ' I2C serial data line
 
SCL            PIN    1                      ' I2C serial clock line
 
SCL            PIN    1                      ' I2C serial clock line
−
 
  
 
' -----[ Constants ]-------------------------------------------------------
 
' -----[ Constants ]-------------------------------------------------------
−
 
 
Ack            CON    0                      ' acknowledge bit
 
Ack            CON    0                      ' acknowledge bit
 
Nak            CON    1                      ' no ack bit
 
Nak            CON    1                      ' no ack bit
−
 
  
 
' -----[ Variables ]-------------------------------------------------------
 
' -----[ Variables ]-------------------------------------------------------
−
 
 
slvAddr        VAR    Byte                    ' slave address
 
slvAddr        VAR    Byte                    ' slave address
 
devNum          VAR    Nib                    ' device number (0 - 7)
 
devNum          VAR    Nib                    ' device number (0 - 7)
Line 58: Line 48:
 
i2cWork        VAR    Byte                    ' work byte for TX routine
 
i2cWork        VAR    Byte                    ' work byte for TX routine
 
i2cAck          VAR    Bit                    ' Ack bit from device
 
i2cAck          VAR    Bit                    ' Ack bit from device
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−
 
−
 
−
 
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' -----[ EEPROM Data ]-----------------------------------------------------
 
−
 
  
 
' -----[ Initialization ]--------------------------------------------------
 
' -----[ Initialization ]--------------------------------------------------
−
 
−
Reset:
 
  
 
   devNum = 0                                    ' device address %000
 
   devNum = 0                                    ' device address %000
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   DEBUG CLS,
 
   DEBUG CLS,
 
         "Line Sensor Demo"                        ' setup output screen
 
         "Line Sensor Demo"                        ' setup output screen
−
 
  
 
' -----[ Program Code ]----------------------------------------------------
 
' -----[ Program Code ]----------------------------------------------------
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   DO
 
   DO
 
       GOSUB Read_Byte                          ' read switches
 
       GOSUB Read_Byte                          ' read switches
−
 
+
                                                ' report
−
      ' report
 
 
       DEBUG CRSRXY, 0, 2, "In.... ", BIN5 i2cData
 
       DEBUG CRSRXY, 0, 2, "In.... ", BIN5 i2cData
 
       PAUSE 100
 
       PAUSE 100
 
   LOOP
 
   LOOP
−
  END
 
  
 +
END
  
  
  
−
' -----[ Subroutines ]-----------------------------------------------------
 
  
 +
' -----[ Subroutines - Don't change nothing here!!! ]----------------------
  
  
 
' -----[ High Level I2C Subroutines]---------------------------------------
 
' -----[ High Level I2C Subroutines]---------------------------------------
−
 
−
' Random location write
 
−
' -- pass device slave address in "slvAddr"
 
−
' -- pass address bytes (0, 1 or 2) in "addrLen"
 
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' -- register address passed in "devAddr"
 
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' -- data byte to be written is passed in "i2cData"
 
−
 
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Write_Byte:
 
−
  GOSUB I2C_Start                              ' send Start
 
−
  i2cWork = slvAddr & %11111110                ' send slave ID
 
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  GOSUB I2C_TX_Byte
 
−
  IF (i2cAck = Nak) THEN Write_Byte            ' wait until not busy
 
−
  IF (addrLen > 0) THEN
 
−
    IF (addrLen = 2) THEN
 
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      i2cWork = devAddr.BYTE1                  ' send word address (1)
 
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      GOSUB I2C_TX_Byte
 
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    ENDIF
 
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    i2cWork = devAddr.BYTE0                    ' send word address (0)
 
−
    GOSUB I2C_TX_Byte
 
−
  ENDIF
 
−
  i2cWork = i2cData                            ' send data
 
−
  GOSUB I2C_TX_Byte
 
−
  GOSUB I2C_Stop
 
−
  RETURN
 
−
 
  
 
' Random location read
 
' Random location read
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Read_Byte:
 
Read_Byte:
 
   GOSUB I2C_Start                              ' send Start
 
   GOSUB I2C_Start                              ' send Start
−
  IF (addrLen > 0) THEN
 
−
    i2cWork = slvAddr & %11111110              ' send slave ID (write)
 
−
    GOSUB I2C_TX_Byte
 
−
    IF (i2cAck = Nak) THEN Read_Byte            ' wait until not busy
 
−
    IF (addrLen = 2) THEN
 
−
      i2cWork = devAddr.BYTE1                  ' send word address (1)
 
−
      GOSUB I2C_TX_Byte
 
−
    ENDIF
 
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    i2cWork = devAddr.BYTE0                    ' send word address (0)
 
−
    GOSUB I2C_TX_Byte
 
−
    GOSUB I2C_Start
 
−
  ENDIF
 
 
   i2cWork = slvAddr | %00000001                ' send slave ID (read)
 
   i2cWork = slvAddr | %00000001                ' send slave ID (read)
 
   GOSUB I2C_TX_Byte
 
   GOSUB I2C_TX_Byte
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   INPUT SCL
 
   INPUT SCL
 
   INPUT SDA
 
   INPUT SDA
−
   RETURN
+
   RETURN</source>
−
</source>
 
  
 
Results:
 
Results:
 
[[Image:LineSensorScreenshot.png]]
 
[[Image:LineSensorScreenshot.png]]
 +
 +
[[Category:Sensors]]

Latest revision as of 10:38, 24 January 2012

This page describes the connection of the i2c line following sensor to the Boe-Bot robot.

LineSensorI2Cphoto.jpg

This sensor uses an i2c bus for connection with the processor. To understand more about the communication, read following two articles:


Please, read the following communication in case of the problems with line detection. And there is a solution: sensors used to be separated from themselves.



The connection diagram:

LineSensorConnection.png

The photo of the connection:

LineSensorPhoto.jpg

The demonstration software: 

'   {$STAMP BS2}
'   {$PBASIC 2.5}

' -----[ I/O Definitions ]-------------------------------------------------
SDA             PIN     0                       ' I2C serial data line
SCL             PIN     1                       ' I2C serial clock line

' -----[ Constants ]-------------------------------------------------------
Ack             CON     0                       ' acknowledge bit
Nak             CON     1                       ' no ack bit

' -----[ Variables ]-------------------------------------------------------
slvAddr         VAR     Byte                    ' slave address
devNum          VAR     Nib                     ' device number (0 - 7)
addrLen         VAR     Nib                     ' 0, 1 or 2
devAddr         VAR     Word                    ' address in device

i2cData         VAR     Byte                    ' data to/from device
i2cWork         VAR     Byte                    ' work byte for TX routine
i2cAck          VAR     Bit                     ' Ack bit from device

' -----[ Initialization ]--------------------------------------------------

  devNum = 0                                    ' device address %000
  slvAddr = $50
  addrLen = 0                                   ' no internal addresses

  DEBUG CLS,
        "Line Sensor Demo"                         ' setup output screen

' -----[ Program Code ]----------------------------------------------------

  DO
      GOSUB Read_Byte                           ' read switches
                                                ' report
      DEBUG CRSRXY, 0, 2, "In.... ", BIN5 i2cData
      PAUSE 100
  LOOP

END




' -----[ Subroutines - Don't change nothing here!!! ]----------------------


' -----[ High Level I2C Subroutines]---------------------------------------

' Random location read
' -- pass device slave address in "slvAddr"
' -- pass address bytes (0, 1 or 2) in "addrLen"
' -- register address passed in "devAddr"
' -- data byte read is returned in "i2cData"

Read_Byte:
  GOSUB I2C_Start                               ' send Start
  i2cWork = slvAddr | %00000001                 ' send slave ID (read)
  GOSUB I2C_TX_Byte
  GOSUB I2C_RX_Byte_Nak
  GOSUB I2C_Stop
  i2cData = i2cWork
  RETURN


' -----[ Low Level I2C Subroutines]----------------------------------------

' *** Start Sequence ***

I2C_Start:                                      ' I2C start bit sequence
  INPUT SDA
  INPUT SCL
  LOW SDA

Clock_Hold:
  DO : LOOP UNTIL (SCL = 1)                     ' wait for clock release
  RETURN


' *** Transmit Byte ***

I2C_TX_Byte:
  SHIFTOUT SDA, SCL, MSBFIRST, [i2cWork\8]      ' send byte to device
  SHIFTIN SDA, SCL, MSBPRE, [i2cAck\1]          ' get acknowledge bit
  RETURN


' *** Receive Byte ***

I2C_RX_Byte_Nak:
  i2cAck = Nak                                  ' no Ack = high
  GOTO I2C_RX

I2C_RX_Byte:
  i2cAck = Ack                                  ' Ack = low

I2C_RX:
  SHIFTIN SDA, SCL, MSBPRE, [i2cWork\8]         ' get byte from device
  SHIFTOUT SDA, SCL, LSBFIRST, [i2cAck\1]       ' send ack or nak
  RETURN


' *** Stop Sequence ***

I2C_Stop:                                       ' I2C stop bit sequence
  LOW SDA
  INPUT SCL
  INPUT SDA
  RETURN

Results: LineSensorScreenshot.png

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