Using a Prop to control the Robo Claw motor controller

charleyshf

Hello,

I am hoping that someone may have used this motor controller with the prop. I haven't seen anything posted on the forums, but the problem I am having is this:

The motor controller is set to packet mode (I need this mode to read wheel encoders which are interfaced to the motor controller).

The manual for the motor controller states:
CRC Checksum Calculation:

All packet serial commands use a 7 bit CRC checksum to prevent corrupt commands from being
executed. Since the Robo Claw expects a 7bit value the 8th bit is masked. The basic CRC checksum is
calculated as follows:
Address + Command + Data = Checksum
To mask the 8th bit you use can a simple math expression called AND as shown below:
Serout P15, i19200, [128, 0, 127, (255 & 0X7F)]

I am using the Extended_FDserial object from the obex along with my program which is attached:

What I cannot figure out is how to get this to work with the roboclaw, you will see by my code I have tried a few different things, and have not had any luck.

I would appreciate any help, thanks

charleyshf

Forgot the link for the manual for the Robo Claw here: http://downloads.basicmicro.com/downloads/datasheets/motor_controller_robo_claw_B0099.pdf

kuroneko

You're getting close. Sending a string doesn't fly (that's about 26 characters you're sending). Using the tx method is OK but ATM you or'ing all values together and send them as a single byte. So what you need is a sequence of 4 tx calls like this:

serial.tx(128)
  serial.tx(0)
  serial.tx(127)
  serial.tx(255 & %01111111)

When that works you can think about using e.g. a loop to pick up the bytes from an array. HTH

charleyshf

Thank you for responding! I've been going through manuals and forums all day today, The code does work, however it works about only 50% of the time. I think I might need more than 1k resistors on my tx and rx lines or maybe even going with a lower baudrate since the motor controller is a 5v device.. Once I get that resolved i'm going to get going on arrays, thanks again.

kuroneko wrote: »

You're getting close. Sending a string doesn't fly (that's about 26 characters you're sending). Using the tx method is OK but ATM you or'ing all values together and send them as a single byte. So what you need is a sequence of 4 tx calls like this:

serial.tx(128)
  serial.tx(0)
  serial.tx(127)
  serial.tx(255 & %01111111)

When that works you can think about using e.g. a loop to pick up the bytes from an array. HTH

kuroneko

charleyshf wrote: »

The code does work, however it works about only 50% of the time.

I don't know much about the BASIC Stamp, could it be that its timing is slightly different (between character time)? I may be talking nonsense here but just to clear that up could you add a pause between the tx calls (e.g. waitcnt(MS_001 * 2 + cnt) for 2ms or maybe more)?

charleyshf

That was it, thank you again! Adding the 2ms delay has made it really stable, now on to arrays...

kuroneko wrote: »

I don't know much about the BASIC Stamp, could it be that its timing is slightly different (between character time)? I may be talking nonsense here but just to clear that up could you add a pause between the tx calls (e.g. waitcnt(MS_001 * 2 + cnt) for 2ms or maybe more)?

charleyshf

I was still having some strange problems with the robo claw controller, so I changed the resistors on the Rx/Tx from 1k to 2.2k and now it works 100% of the time...