The bit positions all have a decimal weight.

Bit position 0 set to binary 1 has a weight of 1

Bit position 1 set to binary 1 has a weight of 2

Bit position 2 set to binary 1 has a weight of 4

Bit position 3 set to binary 1 has a weight of 8

If all 4 bit positions are set then the decimal value would be 15. 1+2+4+8=15

Thanks @Robot Doc.

All these "bit", "bytes", "16-bit values", "high bytes", "two’s complement" notions are completely new to me. But I think I get it...

So, to take the same example, if there is both a "Bump Left" and a "Wheel Drop Left", it will correspond to a bit position 1 (weight of 2) + a bit position 3 (weight of 8) and so, in the script, the $x value will be 10. Right?

Use GetBit()

$x = 2

if (getbit($x, 0))

  print("Bump Right")

endif

if (GetBit($x, 1))

  print ("Bump Left")

endif

if (GetBit($x, 2))

  print ("Wheel Drop Right")

endif 

if (GetBit($x, 3))

  print ("Wheel Drop Left")

endif

I am at work now.... i will check this thread later when i get home.... i think this script i wrote for the 400 series roomba.... i think the baud rate is wrong for the 600 series. .. @Doc can help you too after all he is the roomba doctor :)

That script is a little rough... and the baud rate is wrong. It should be 115200 not 57600... The 600 series uses 115200 baud.... also you only need to initialize the UART once.....

@Richard' you are right. I already have modify baud rate and, as I said, the script works just fine (that's why it is not "required assistance thread" ).

But I want to better understand the way ARC and Roomba OI works together to go further in my future scripts, and your script was a good example to illustrate what I understand and what I don't...

@DJ, thanks for the tip and the script example

@fredebec... Ok no worries..... I have another script that can read 2 byte data like Roomba battery voltage.... I'll post it for you tomorrow (my time) afternoon when I get home from work...

fredebec

Quote:

So, to take the same example, if there is both a "Bump Left" and a "Wheel Drop Left", it will correspond to a bit position 1 (weight of 2) + a bit position 3 (weight of 8) and so, in the script, the $x value will be 10. Right?

Yes, you got it !

@DJ, Ok, I see why it is interesting to use GetBit(). But now, I don't understand where the $x=2 come from....

The function is GetBit(Value, Bit). Why the value is $x=2 in that case ?

Thank you all for your help.

@Richard, thank you for your scripts, it helps me a lot to have concrete examples.

@fredebec Here's another example for getting the roomba's battery voltage and charge state.... This example is using UART 0, however...

uartinit(0, 0, 115200) #initialize UART port 0
  sleep(100)
 $RX_DATA=0
  uartWrite(0,0,142,22) # Volatge check
  sleep(50)
  uartWrite(0,0,142,21) # charge state
  sleep(50)
  $rx = UartAvailable(0, 0)


  if ($rx=3)
    $RX_DATA = UARTRead(0, 0, $rx)
    $MSB=GetByteAt($RX_DATA,0)
    $LSB=GetByteAt($RX_DATA,1)
    $Charge=GetByteAt($RX_DATA,2)
    $voltage=($LSB+(256*$MSB))/1000
   
      print("Battery Voltage = "+$voltage)

    if ($charge=0)
      print("Roomba is not charging")
      elseif($Charge=1)
      print("Roomba is recondioning charging")
      elseif($Charge=2)
      print("Roomba is fast charging")
      elseif($Charge=3)
      print("Roomba is trickle charging")
      elseif($Charge=4)
      print("Roomba is waiting to charge")
      elseif($Charge=5)
      print("Roomba is not charging/Fault")
    endif
   
  endif

Quote:

The function is GetBit(Value, Bit). Why the value is $x=2 in that case ?

The value of $x=2 just means that if bit position two is set to a 1 then "Wheel drop right" should be happening.

@Robot Doc, now I think I am lost again :D

When you say "is set to 1", you mean "the state of the bumper/wheel drop is 1", with 0 ($x=1) = no bump/wheel raised and 1 ($x=2) = bump/wheel dropped. Am I correct ?

@Richard, thanks for the script. I will test it as soons as I can.

Each bit position represents the state of a single sensor. If the bit position is storing a 0 then the sensor is off. If the bit position is storing a 1 the the sensor is on.

I just used a $x to set a fake value to demonstrate the rest of the code. It's merely a place holder for the demo to run.