Replacing A4988 Drivers with DRV8825 on Arduino Mega 2560 + Ramps

[PyramidDave]

What I do not understand is how I have been using it successfully for 1.5 years without this problem & all of a sudden I have a problem. If the fact that USB does not support real time protocol played into this problem, wouldn't I have had a problem a long time ago? I have 2 to 3 thousand hours of printing on this printer.

What electronics are you using on your printer and how do you connect to it?

[Mjolinor]

So if you jumped out of a bedroom window every day for a year and didn't break a leg then one day you did break your leg you would assume your house had grown?

That is exactly the same scenario.

I use a Flashair SD card and connect over my home network.

I am not saying your USB is not at fault in terms of functional hardware but I am saying that your conclusion is not valid based on your input data.

[PyramidDave]

I had not thought about using a wireless SD card. That is an interesting way to print. Thanks.

[kd7eir]

Why do you think there is something wrong with it?

No amount of changing hardware is going to alter USB specifications. They are written by a standards committee and they are written in such a way that they are not suitable for real time communications.

I have hundreds of hours of printing using a Raspberry Pi and OctoPrint and have never had a single communications error.

[Mjolinor]

I have hundreds of hours of printing using a Raspberry Pi and OctoPrint and have never had a single communications error.

And? Do you think this somehow changes the written specifications of the standard?

Lots of people have hundreds of hours with no problem but then again, lots of people jump out of windows and don't break legs.

[kd7eir]

And? Do you think this somehow changes the written specifications of the standard?

Lots of people have hundreds of hours with no problem but then again, lots of people jump out of windows and don't break legs.

It PROVES that it works in spite of "experts" like you trashing it.

You have contributed NOTHING to this discussion. People come here for help, not pedantic lecturing. Eat a Snickers, maybe you'll feel better.

[Mjolinor]

I have not once said it will not work.

I have said that if you have problems then you may not be able to fix them and stated the reasons for that.

I have also said that even if you do not have problems it is likely that some day you will.

That, my pedantic friend is a lot more useful than "mine works so it''s OK".

If you do not like the advice then go elsewhere or ignore it, personal attacks on people do not help.

[printbus]

What I do not understand is how I have been using it successfully for 1.5 years without this problem & all of a sudden I have a problem.

It could be that a windows update, installation of some other software using USB, an update to your host software, or Marlin updates (if you installed any) changed some details in how USB is working.

I had not thought about using a wireless SD card. That is an interesting way to print. Thanks.

Note that it seems the majority of people using Flashair SD cards are running Sailfish firmware on their printer. If you search for info, you'll find that it can take some effort to get them working under Marlin. Marlin accessing the SD card contents evidently disables the wifi on the card.

[Mjolinor]

I use a Flashair on my Wanhao with Sailfish and on my laser cutter and CNC router both of which use Marlin.

I think the newer Flashair is harder though I have no experience of that just that CA can't get his to work at all.

[PyramidDave]

It should not be a Windows driver problem since printing it from the SD card or from octoprint caused the same problem. I went thru & took all the connections apart & back together. I had not pulled the Ramps apart from the Arduino before. I also swapped a P/S supply out since I had a spare. The P/S was not the same brand, but has the same power rating. The Printer had the same problem with the other P/S, so unless that P/S was bad also, it should not be that. I am doing a 2 hour test print without Heatbed & relay in the circuit. It failed when I printed without the Heatbed, but still had the relay attached. Colin did not think that was it, but thought I would test it anyway while I was in test mode. I bought this replacement Arduino board set http://www.ebay.com/itm/3D-Printer-K...UAAOSw3mpXIYRN & will swap that out if this next print fails.

I made this change in the configuration.h file before uploading the new firmware. Colin told me to double the numbers for the DRV8825 drivers.

//For DRV8825 drivers
#define DEFAULT_AXIS_STEPS_PER_UNIT {160,160,8000,1730} //For A4988 drivers {80,80,4000,865}