Removing LCD SD Card in Mid-Print?

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Gwhite
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Removing LCD SD Card in Mid-Print?

Post by Gwhite » Sun Mar 11, 2018 10:43 pm

I looked around, but couldn't find an answer to this.

I load my print files onto an SD card from my computer. I then pop the card into the LCD box & fire up a print.

Here's my question: Does the printer print directly from the LCD, or does it load the file into some form of local memory at the beginning of a print? I'd like to remove the SD card once the print gets going to set up the next job.

I can always get another SD card, and alternate between the two, but I was curious to know if you can remove the SD in mid-print without killing the current print job. I'm guessing no.

Thanks!

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ednisley
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Re: Removing LCD SD Card in Mid-Print?

Post by ednisley » Mon Mar 12, 2018 12:42 pm

Gwhite wrote:does it load the file into some form of local memory
The Arduino-class microcontroller used in the RepRap family of printers has 8 kB of RAM, so, to a very good first approximation, it has no memory at all.

A ring buffer holds a few G-Code commands in RAM to smooth the serial data flow and provide lookahead for the path planner, but the hardware allows nothing more.

Which also explains Marlin's sparse mesh leveling: there's no space for more than a coarse grid of probe points.

Gwhite
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Re: Removing LCD SD Card in Mid-Print?

Post by Gwhite » Tue Mar 13, 2018 2:22 am

Thanks! That's kind of what I figured. I scrounged up an old 512 Mbyte SD card, to swap back & forth. I checked a bunch of print files, and the biggest I could find was only 5 Mbytes...

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ednisley
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Re: Removing LCD SD Card in Mid-Print?

Post by ednisley » Tue Mar 13, 2018 1:41 pm

Gwhite wrote:an old 512 Mbyte SD card
It's the last, best use for tiny cards! [grin]

They do wear out, however, even under what should be minimal use. When weird failures start happening, put the same file on the other card, then see if the problem follows the card or the file.

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