Stop is not correctly implemented?

[nova76]

here's the code

if (stepCommand == ACCELSTEPPER_STOP) {
if (stepper[deviceNum]) {
stepper[deviceNum]->stop();
isRunning[deviceNum] = false;
reportPosition(deviceNum, true);
}
}

But the accelstepper library cannot handle the quick stop. Therefore, the deceleration must be waited before the stepper motor stops. Is the report too early?

[soundanalogous]

Have you tested this? If so which Firmata client library did you use?
@dtex FYI

[nova76]

ConfigurableFirmata 2.10.1
AccelStepper 1.58.0

It is not certain that this is a bug, maybe the author knowingly did this. It was a little confused for me,

When we issue the stop command to the motor, it doesn't stop yet. See stop command in accelstepper library (https://www.airspayce.com/mikem/arduino/AccelStepper/classAccelStepper.html#a638817b85aed9d5cd15c76a76c00aced). It only starts the deceleration So it doesn't complete, only stop/complete with just a few cycles later, if you set a deceleration parameter. The question is, can an earlier function be evaluated as correct? Is running the motor? Yes, it's running (it's rotating), but the stop process has started.

So, I think this would be correct (if there is a deceleration):
// isRunning[deviceNum] = true;
reportPosition(deviceNum, false);

[dtex]

I wouldn't expect it to report the position prior to the stop completing, but it sounds like that's what you are describing. I'll take a look after work tonight.

[dtex]

I'm not with hardware yet, but it looks like it will report the position twice. Once when stop is fired and once when the deceleration has stopped.

[dtex]

I'm running AccelStepper 1.23.0 and it stops immediately which is by design. I made a conscious decision to stop immediately even when acceleration is used. Here was my reasoning.

Is it decelerating when stopping for you? Perhaps something changed in accelStepper?

[jcvillegasfernandez]

I am trying to make a Lazarus client (pascal) and in my tests found Stop function does not work properly, it stops suddenly not smoothly.

Looking in the source code I think I found the problem, it works for me.

In AccelStepperFirmata.cpp file I removed or commented two lines

else if (stepCommand == ACCELSTEPPER_STOP) {
if (stepper[deviceNum]) {
stepper[deviceNum]->stop();
// isRunning[deviceNum] = false; // Line to comment
// reportPosition(deviceNum, true); // line to comment
}

[dtex]

It was a conscious decision to have stop not decelerate based on the use cases I imagined (limit switches and panic buttons). Tell me about your use case.

[jcvillegasfernandez]

I personally prefer a smooth stop but I agree with you in some cases it is better to stop suddenly (if you have limits like a garage door hitting your car), but that can cause problems too, imagine a motor with heavy load, that means a lot of inertia can cause problems.
The other problem is inconsistency because after a stop if you run motor again it starts at the speed it stopped (usually full speed).
Perhaps the solution will be two different stop functions or an enable disable sudden/smooth stop.

[dtex]

Ah, so we should definitely update the current speed. Let me look into how accelStepper would handle an immediate stop when a stepper has deceleration.

[soundanalogous]

The AccelStepperFirmata documentation for the Stepper stop command does state "If an acceleration is set, stop will not be immediate". I propose we add a second command, one stopping immediately, the other decelerating until stop.

[jcvillegasfernandez]

Or maybe a little modified stop command like this
0 START_SYSEX (0xF0)
1 ACCELSTEPPER_DATA (0x62)
2 ACCELSTEPPER_STOP (0x05)
3 device number (0-9)
4 Stop_smoothly (0-1) // optional to send, that makes compatibilty
4 or 5 END_SYSEX (0xF7)

[jcvillegasfernandez]

Because I need to continue developing my Lazarus client I definitely changed the source code of AccelStepperFirmata, commenting the two lines, so I have a smooth stop now, when I need a sudden stop I have implemented a faststop function, setting Acceleration to max_acceleration, then calling stop (in this case with max deceleration) and then set normal acceleration again.

[LinuksGuru]

Is abrupt stop problem can be only solved as jcvillegasfernandez suggests or there update with fix on the way?