Search found 23 matches

by ChrisA
Thu Mar 14, 2019 2:03 am
Forum: General Discussion
Topic: How fast can a Roboclaw process commands?
Replies: 5
Views: 944

Re: How fast can a Roboclaw process commands?

It is the normal python driver but I've been placing every every attempt to communicate with the serial port in a try ... except block. Mostly comm failures are ok because the control loop will just cycles and we try again on a few milliseconds. With try-except we don't crash the program, we just lo...
by ChrisA
Tue Mar 12, 2019 2:17 pm
Forum: General Discussion
Topic: How fast can a Roboclaw process commands?
Replies: 5
Views: 944

Re: How fast can a Roboclaw process commands?

Just as an aside, we can't send a long sequence of comands into a robot. The problem is that wheels slip and the wind vlows and the ground is not flat so we must continously measure where the robot is relative to the desired location and correct it. So we use IMU, GPA and cameras to track location w...
by ChrisA
Tue Mar 12, 2019 1:46 pm
Forum: General Discussion
Topic: RoboClaw 2x15A Motor Controller (V5E) - Freeze/Hang
Replies: 3
Views: 772

Re: RoboClaw 2x15A Motor Controller (V5E) - Freeze/Hang

I see the same problem using ROS I get hangs and freezes. Then I added a write timeout and now get timeout exceptions. The problem might be in Py Serial. Without setting the write timeout i would hang "forever" but the timeout prevents that Here is my modification to roboclaw_driver.py (write_timeou...
by ChrisA
Tue Mar 12, 2019 3:39 am
Forum: General Discussion
Topic: How fast can a Roboclaw process commands?
Replies: 5
Views: 944

How fast can a Roboclaw process commands?

How fast can a Roboclaw process commands in serial packet mode over USB? I'm sure that must be a limit. Why do I ask? I'm using ROS and the "roboclaw_node" base controller node. This roboclaw_node, on it's own reads both encoders 10 times per seconds and also reads out all the diagnostic data (volta...
by ChrisA
Tue Mar 12, 2019 3:06 am
Forum: General Discussion
Topic: Many intermittent failures with serial packet
Replies: 6
Views: 1092

Re: Many intermittent failures with serial packet

I am connecting the USB port on the roboclaw to the USB port on the Raspberry Pi3 using a short USB cable. My guess is that it should be reliable because USB uses differential signaling. Would it be more reliable to use the 5 volt serial pins on the roboclaw? But that means level converting the 3.3 ...
by ChrisA
Mon Mar 04, 2019 4:48 pm
Forum: General Discussion
Topic: Many intermittent failures with serial packet
Replies: 6
Views: 1092

Re: Many intermittent failures with serial packet

I have more information: The Roboclaw is hanging on writes. I changed the last function in roboclaw_driver.py to this: def Open(comport, rate): global port port = serial.Serial(comport, baudrate=rate, timeout=0.1, interCharTimeout=0.01, write_timeout=0.1) return The only change was to add "write_tim...
by ChrisA
Mon Mar 04, 2019 12:05 pm
Forum: General Discussion
Topic: Many intermittent failures with serial packet
Replies: 6
Views: 1092

Many intermittent failures with serial packet

Reading encoders values fails intermittently. I am using the ROS roboclaw_node Python node which makes calls to the python roboclaw driver. Specifically, it calls roboclaw.ReadEncM2() and roboclaw.ReadEncM1() 10 times per second. The Roboclaw is connected to a Raspberry Pi3b with a USB cable I notic...
by ChrisA
Sat Mar 02, 2019 6:49 pm
Forum: General Discussion
Topic: Roboclaw shuts down and needs power cycle
Replies: 1
Views: 461

Roboclaw shuts down and needs power cycle

I'm using a Roboclaw 2x15A with the ROS driver and of course, in turn, it uses the python driver. I'm sending commands over USB from a Raspberry Pi3. Sometimes (I think) one of the two sides will detect an overcurrent and shut down. After that sending more command does nothing. The side not shut dow...
by ChrisA
Sat Mar 02, 2019 6:21 pm
Forum: General Discussion
Topic: Four motors?
Replies: 2
Views: 573

Re: Four motors?

Yes, this is correct you can wire the motors in parallel. The motors will all run at the same speed as long as all of the wheels are firmly planted on the ground. But if a wheel "catches air" its motor will become unloaded and spin faster than the one that is still in contact with the ground. What h...
by ChrisA
Fri Feb 15, 2019 3:02 pm
Forum: General Discussion
Topic: Roboclaw stops with all LEDs off, power cycle required
Replies: 3
Views: 855

Re: Roboclaw stops with all LEDs off, power cycle required

How long do the LEDs flash on power up? On power up I see a green flash that lasts as long as a lightening bolt, not long enough to check of both green LEDs are lit or just one. It could also be that the green flash is so bright it overpowers the red flash. Is there some way to force the red LED to ...