Is printing from SDCARD faster than from USB?

AETEK

Hello,
Is printing from an SDCARD connected directly to the 3D printer motherboard faster than via the serially connected USB port?

The USB port is serially connected to the ATMEGA2560 via the CH340 chip with 250kbit. 250000/8 = 31.25k Bytes per second. The SD CARD connected directly via the ATMEGA's SPI bus can deliver a data rate of approx. 500K bytes / second @8MHZ SPI speed.  Thus it is clear which interface is faster. But does this affect the printing speed of the 3D printer in everyday life?

Has anyone checked?

Note:
In the A5, the USB stick, USB port and SD card are all connected via the serial interface. In this case, the printing time will not change.

Samuel Pinches

This is an interesting topic - I look forward to hearing your results. I remember seeing two videos on this topic of “speed wall”:

https://youtube.com/watch?v=ySqj3gPqfrs

https://youtube.com/watch?v=SBZ7MfvAsGc

AETEK

Hello,
thanks for the links to the two videos. Especially the second video answers my question. The processor is not an Arduino, but an ATMEGA2560. This is a RISC processor that is very efficient. Tie MCU at 16MHZ process 16 million commands per second. Although the computational effort of the Marlin firmware is beatchlich, so in my opinion, the mechanics of the 3D printer is the limit. At high printing speeds, the mechanism tends to vibrate, resulting in inaccuracies.

With a faster data transfer to the ATMEGA2560, the processor has the data to be provided sooner available and therefore more time to calculate the travel paths ahead. In this context, it would be worth trying to enlarge the receive buffer (16 commands) when printing from SD card. Marlin offers this option. The ATMEGA2560 still has enough unused RAM. Other, smaller MCUs may not.

Addendum:
ATMEGA MCUs can also be overclocked.

I have already done that with other applications.

There, the MCU ran without problems @ 25 MHz.

sanjibukai

Hi,
However I don't think that reading filesystem from USB is the same as receiving the serial data from USB..
It would be worthwhile to test from SD Card then from USB Stick.
I don't have yet good printer settings, but as soon as I do I will do the test (plus in vase mode!)

AETEK

Hello,
You can not do this test with the A5, because the connection of USB and SD card in the A5 both works serially via the additional MKS TFT28 touch display. To do this, you need another 3D printer with monochrome display incl. SD card reader.
cheers

https://youtube.com/watch?v=SBZ7MfvAsGc

sanjibukai

Hi I saw this video from earlier post..
But I just figured out your note in the first post:
> @AETEK : Note: In the A5, the USB stick, USB port and SD card are all connected via the serial interface. In this case, the printing time will not change.

So, basically does this mean that in this printer we will be limited to 45-50 mm/sec speed?

Maybe, this is why you want to upgrade some part in the other post, right?

AETEK

Hello,
no, you are not limited to 45mm / s. It depends on which GCODE dataset has to be transferred. Especially with circles, the amount of data is higher than in straight.
Yes, the SD card with monochrome display is faster because the connection is not made via the serial port. But the problem is the beautiful, colored touch screen. It has too many limitations and is not expandable with the current MKS firmware. There is currently no way to integrate additional functions. In addition, the display has much less setting options compared to the 4x20 character display. I also like the operation with the rotary encoder better. I can navigate faster in the menus.

Cheers

sanjibukai

Totally agree about the rotary in some situations..
And yep, I mean 45 for circular shapes as mentionned in the video from tech2c..

And how about printing with octopi?
Is it slower or faster (or not relevant)?

AETEK

Octopi -> USB ->  CH340 Chip -> Serial -> Marlin

So it is the same as printing via MKS Display SD Card or USB Stick.

cheers