fredebec
Hi,
I have finally found a Roomba 620 I wish to use as a robot base. Everything works great, thanks to @RichardR examples and some very interesting threads. Now I try to fully understand UART functions and the Roomba Open Interface, and sometimes it is a bit confusing... So, at this point I need some expert enlightenments.
Here is an example I don't understand:
Richard R made a script for object avoidance and it works great :
Quote:
:top $drive=1 uartinit(0, 2, 57600) #initiate UART port 2 (pins 18 Tx and Pin 19 Rx) sleep(20) uartWrite(0, 2,128,132) #Init iRobot create and place in full mode sleep(20) uartWrite(0,2,137,0,125,128,0) #forward slow$x=0 REPEATUNTIL($x>0)
uartWrite(0,2,142,7) #Roomba Bump and wheel drop sensor
IF (UARTAvailable(0,2)>0) $x=UARTRead(0,2,1) $x=GetByte($x)
ENDIF print($x)
IF ($x=2) # left bumper hit uartWrite(0,2,137,255,155,128,0) # back up sleep(1000) uartWrite(0,2,137,0,100,255,255) #turn right sleep(2000) ELSEIF ($x=1) # right bumper hit uartWrite(0,2,137,255,155,128,0) # back up sleep(1000) uartWrite(0,2,137,0,100,0,1) #turn left sleep(2000) ELSEIF ($x>2) # centre bump or wheel drop uartWrite(0,2,137,255,155,128,0) # back up sleep(1000) uartWrite(0,2,137,0,100,0,1,157,0,180,137,0,0,0,0) #turn around 180deg sleep(2000) ENDIF
sleep(20) ENDREPEATUNTIL goto(top)
But I don't understand the GetByte values: $x=2 correspond to "left bumper hit", $x=1 to "right bumper hit" and $x>2 to "centre bump or wheel drop"... but when I look at the OI documentation :
I don't see the fit with the bit values and I don't see how the Range could be 0-15 with only one byte...
Thanks for the help and sorry if it is a stupid question (I am afraid it will not be the last
)
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()
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
Yes, you got it !