I'v got this USB/SD card/CompactFlash reader from an old DELL AIO 926 printer, it's a double sided PCB board and that's all i know about it. I tried to google it but couldn't find anything relevent, how can i tell what voltage it takes and what each wire does and how to interface it with arduino?

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It seems to me that it has two sets of 4 wires (red/orange - black - yellow - white) and an extra blue wire, i'm guessing that the black is for GND, red/orange for VCC, yellow/white for SDA/XDA I2C serial bus data transfer, but no clue what the blue wire does, i could've tested this with arduino but i don't want to risk frying the board by using a wrong voltage. any help would be greately appreciated. thanks.

  • If the end is a USB that presumably can work when plugged in to computer, why dont you try it with Raspberry Pi?
    – NoBugs
    Jan 7, 2018 at 20:53

1 Answer 1


I can pretty much categorically say you won't get it working.

I have a similar board here with the same SMSC (now owned by Microchip) chip on it.

The interface is USB plus some other signals. I have managed to identify the USB portion of the interface on mine, but not the other signals.

The SMSC chip has the option of using an external ROM chip to store its program, and Dell love to do that. So, it has a custom firmware which means it doesn't get recognized by my computer without Dell's specific drivers installed. So it's useless.

There's a very very slim chance you may get it working with a USB Host Shield, but unlikely - and at the end of the day, what's the point? It's just an SD card reader. Wire an SD card socket direct to the Arduino and save yourself both the headaches of trying to work it out and also the massive pointless expense in buying the hardware you'll need to do the interfacing.

  • Well it would've been nice to use it as usb host and sd card reader, but what i really want is to learn how to hack such boards. Do you know what voltage should i use as VCC? and do you have a datasheet link to the smsc chip?
    – razzak
    Jun 22, 2015 at 19:03
  • Vcc would be 5V as it's USB. My board actually has a slightly different SMSC chip looking at it - similar thing, but a little newer (and that one is obsolete too). Getting a datasheet for that very old one would be hard. I'll see what I can do.
    – Majenko
    Jun 22, 2015 at 19:05
  • Looks like a no-go. I could beg the guys at Microchip to head down to the archive room and see if they can dig out an old datasheet in their files, but it won't help you to get it going on an Arduino. The SMSC chips are pretty much all 8051 based internally, so if there is an external ROM you could wire that up and read off the program from it and disassemble it to see how it works, but that'd be a huge job with no real reward at the end of it (other than a knowledge of old 8051 assembly). I'd just strip the useful components off it to use elsewhere. Maybe try and rescue the sockets, etc.
    – Majenko
    Jun 22, 2015 at 19:12
  • It does sounds like a huge job for a hobbiest like me, i would probably strip it from its coponents and throw it in the bin soon, thanks for your help.
    – razzak
    Jun 22, 2015 at 19:19
  • Actually, it looks like someone may have already had the ROM chip off it...
    – Majenko
    Jun 22, 2015 at 19:29

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