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====== Reflection sensors ======

===== Idea =====

A reflection sensor is most of the time a sensor that uses (infrared) light to detect the precence of an object.

===== TCND5000 the demonstrated sensor =====

|{{https://user-images.githubusercontent.com/11397265/154144243-3562aae3-f703-405f-9148-8460dfb92e05.jpg?400|TCND5000}}                                |{{https://user-images.githubusercontent.com/11397265/154144262-307428fa-ce24-453f-a98e-5db9d4db09f9.jpg?400|Sketch schematics}}           |
|{{https://user-images.githubusercontent.com/11397265/154559970-26f69aa7-d06c-43a0-a1d3-ee4ff6014d69.jpg?400|Cosey floor sensors on the front side sm}}|{{https://user-images.githubusercontent.com/11397265/154144288-a7196a4c-be4e-4c2a-8405-c2779fa51ce2.jpg?400|Reflection sensor schematics}}|

**Upper left:** The TNCD5000 is a sensitive photo diode and an infrared led in one case.\\
**Upper right:** A sketch of the TCND5000 driver.\\
**Lower left:** Five sensors mounted on Cosey's PCB.\\
**Lower Right:** Piece of schematics of the Cosey robot, note that the resistor values have changed!


----

===== Pseudo code =====

<code>
Function: REFLECTION  ( adc -- +n )
  Read adc input 'adc' leave the reading '+n'

Function: FLOOR  ( adc -- +s )
  Read adc input 'adc' and leave the scaled result '+s'

Function: RAVINE  ( -- 0|1|2|3 )
  Read the three adc inputs from the front of a robot.
  Translate the results to the numbers 0 to 3, indicating
  which sensor(s) where fired. Zero means non.

Function: BACKWARD?  ( -- flag )
  Test the sensor on the backside of a robot, leave true
  if the sensor is fired, otherwise false
</code>

===== Generic Forth =====

<code forth>
\ Reflection sensor example as used with the Cosey robot
\
\ Each sensor output is connected to an ADC input with 12-bit resolution
\
\ Words with hardware dependencies:
\ : **BIS       ( mask addr -- )      tuck @ or  swap ! ;
\ : **BIC       ( mask addr -- )      >r  invert  r@ @ and  r> ! ;
\ : BIT**       ( mask addr -- 0|b )  @ and ;
\
\ Needed an ADC routine like this one for the MSP430FR5949:
\
\ We need to clear the ENC bit before setting a new input channel
\ ADC can be used with VCC and VREF (2.5V) as reference voltage
\ : ADC         ( adc fl -- +n )
\    02 800 **bic               \ ADC12CTL0  Clear ENC
\    100 and >r                 \ Use VREF when fl is true
\    1F and  r> or 820 !        \ ADC12MCTL0 Select input
\    03 800 **bis               \ ADC12CTL0  Set ENC & ADC12SC
\    begin 1 802 bit** 0= until \ ADC12CTL1  ADC12 busy?
\    860 @ ;                    \ ADC12MEM0  Read result
\
\ Activate an output on a PCA9632 I2C led output driver
\ The routine /MS waits in steps of 0.1 milliseconds
\ It is used here to give the sensor time to settle
\ : >ON         ( b -- )        8 >pca  1 /ms ; \ b = 1, 4, 10 or 40

\ Read sensor level from input 'adc' using VCC as reference
: REFLECTION    ( adc -- +n )    0 adc ;

\ FLOOR sensor result is scaled and gives a number from 0 to 10
: FLOOR     (  adc -- s )       reflection  180 / ;


\ Examples (Cosey's advanced commands):

\ 0 = No ravine             Table edge detection
\ 1 = ravine at left
\ 2 = ravine in front
\ 3 = ravine at right
: RAVINE           ( -- 0|1|2|3 )
    01 >on  01 floor 5 < if  3 exit  then   \ Right sensor
    04 >on  02 floor 5 < if  2 exit  then   \ Middle sensor
    10 >on  05 floor 5 < if  1 exit  then   \ Left sensor
    0 ;         \ No floor sensor at all triggered

\ True if reflection sensor on the backside goes over the edge
: BACKWARD?         ( -- f )    10 >on  0E floor 5 < ;
</code>

More info look at specific implementations, if any.

**Cosey robot V1.0** {{https://user-images.githubusercontent.com/11397265/154557981-a7b3d33a-0dc0-47c8-b40c-a01395871c94.jpg|Cosey V1 0}}