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Topic: Providing USB interface for device with only SD card port (Read 581 times) previous topic - next topic

TiredKorok

Hi,

I've been looking into this topic for a while and I've found something that seems to be exactly what I need:
https://www.maximintegrated.com/en/products/interface/MAX14502.html



I'm a software engineer not an electrical engineer so this is pretty far out of my comfort zone.
I just want to make sure before I order the evaluation kit that this would be able to accomplish what I want and to also ask for advice.

Is there a better choice?
Once I get the evaluation kit and work out how to control the chip modes, can you point me into the right direction of where to start designing my pcb. Maybe a guide or a place to get it printed in *very* low runs?

I intend to use an arduino to control the chip, so my current idea is to design the bridge as a hat for the arduino. Is that reasonable?

I appreciate any help, thanks -
Asher

DrAzzy

I'm not sure if that does what you want - it looks to me like to get USB to talk to the chip, it still needs to be controlled by a processor with USB support. It looks like it allows both the USB port and the processor to directly access the SD card, while still providing USB access to the processor, which would have to support USB. Notice how the diagram shows a USB-PHY connection to the processor. It may also require an "SD interface" (an Arduino using an SD card uses it in SPI mode).
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TiredKorok

I think I see what you mean, it really is unclear to me. I've been back and forth whether it's what it seems to me or not.

For instance, quoting their news letter found here:
https://www.maximintegrated.com/en/aboutus/newsroom/newsroomall.enproducts1462.html

    "Maxim's new Hi-Speed USB-to-SD card bridge delivers up to 40x the boost to SD card read/write speed in portable
        applications...

    Its integrated processor eliminates the need to develop a software driver...

    The MAX14502 thus eliminates the time-consuming and complicated task of developing a software driver, allowing
        designers to effortlessly add Hi-Speed USB to their applications."

Which sounds to me like exactly what I'd want! However looking at the diagrams like this one:

Just make me more uncertain...

I see the SD Interface that you're talking about, and to me this seems like a chip designed to
    1) keep the sd card ports of a device
    2) add a usb port
    3) use of up to two sd ports and one usb port on the target device
    4) allow a passthrough mode for sd cards & usb device directly to host processor's ports

What do you think?

JohnRob

Its not clear what you are trying to accomplish.

I have a hand full of USB to SD card adapters for my camera etc.  So I'm assuming you want something else.

I also just completed a project that connected an SD Card to an Arduino Pro Mini.  It was actually quite simple since the µSD card is basically a SPI device.

John

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DrAzzy

yeah, looking at that second diagram, it seems pretty clear to me that it does what i described in my post above.

It might be possible to use a serial adapter chip instead of the microcontroller if that's what you want - but it still looks like it needs an SD interface (the 6-wire kind with 4 data lines), which is a feature of some more advanced microcontrollers, but not the AVR based ones, and which is rarely used in Arduino land - accessing it via SPI may or may not work.
ATTinyCore and megaTinyCore for all ATtiny, DxCore for DA/DB-series! github.com/SpenceKonde
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

JohnRob

Quote
but it still looks like it needs an SD interface (the 6-wire kind with 4 data lines), which is a feature of some more advanced microcontrollers, but not the AVR based ones, and which is rarely used in Arduino land - accessing it via SPI may or may not work.
@DrAzzy

I'm curious at what I might be missing here.  From what I was able to gather the 6-wire interface is for some extended functions.  Not sure what they were.... I guess if you want to use the Hi Speed mode.

To simply communicate with an SD card from an Arduino borders on trivial.  I have one running now on an Arduino M0, but earlier I tested it with an Arduino Pro Mini.

The only issue I had is the MISO line is not tri-state by the SD card, nor a number of SD card breakout boards.

John
Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.

DrAzzy

I just don't know whether that chip (through which communication with the sd card must pass) will support spi, is the thing.
ATTinyCore and megaTinyCore for all ATtiny, DxCore for DA/DB-series! github.com/SpenceKonde
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

JohnRob

I guess what I'm saying is;  I don't see the need for that chip at all, unless you want to use the highspeed mode.

For what it's worth,  in my recent SD card project using an Arduino M0, I "printed 8 values each with a  comma in between for a total of 15 print statement.  The time required was just short of 20 ms.


Will be interesting if the OP comes back with more information on their goal.

John
Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.

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