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MOBI
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Joined: 02/12/2012
Location: Australia
Posts: 819

Posted: 04:28pm 06 Mar 2013

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I have wired up my SD card - that's the easy part as there are only 9 pins and two not used.

The schematic for the MM shows three terminals for the write protect etc. I have a number of SD card holders which are all different and appear to do different things when the card is inserted with the lock on or off.

Can anyone tell me the switching arrangement of the three terminals on the schematic?

Internet searching is sending me crosseyed and couldn't find a previous post on TBS.

David M.

aargee
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Joined: 21/08/2008
Location: Australia
Posts: 255

Posted: 05:34pm 06 Mar 2013

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I'm pretty sure the "write protect" and the "SD card present" switches are active low. You can hard wire them if you like, the MM software will then assume a card is present.

For crying out loud, all I wanted to do was flash this blasted LED.

MOBI
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Joined: 02/12/2012
Location: Australia
Posts: 819

Posted: 05:53pm 06 Mar 2013

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aargee said I'm pretty sure the "write protect" and the "SD card present" switches are active low. You can hard wire them if you like, the MM software will then assume a card is present.

Thanks, sounds like a plan to me. Hard wiring is the easy option - perhaps I leave them un soldered and just plug a jumper in the appropriate breakout board headers.

I did notice that when I plugged the card in, the card holder case connected to the other pins but not all the card holders had the same physical layout and not all connected to the case (ground).

I wasn't sure if a card was switched as "present" but not actually there would cause an operational hiccup.

David M.

bigmik

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Joined: 20/06/2011
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Posted: 08:21pm 06 Mar 2013

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aargee said I'm pretty sure the "write protect" and the "SD card present" switches are active low. You can hard wire them if you like, the MM software will then assume a card is present.

I think you will find `WP' is active HIGH..

Ie. If high then write protect, If low then Write enable

See table below

Regards,

Mick

Edited by bigmik 2013-03-08

Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<

MOBI
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Location: Australia
Posts: 819

Posted: 09:16pm 06 Mar 2013

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@Mick

I guess then that D5 and D6 have internal pull ups as the WP and Det only connect to ground.

All the conditions in the table refer to when card ejected - I'm a little confused.

I can't see that I'll do any damage by tying the D5 and/or D6 low without the card in, so I'll experiment and see what errors come up. Just as well I have headers to plug into.

Don't know why SD card holders (except for pins 1 to 9) have to be so different wrt wp and det.

David M.

bigmik

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Posted: 11:53pm 06 Mar 2013

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Sorry David,

Yes that is a very bad example, I apologise, I saw it in amongst the many data snippets I have from when I designed the UBW32-MCC PCB and didnt read it properly.

Basically the D5 and D6 pins have internal pullups and the D5 is LOW when card is INSERTED and HIGH when EJECTED.

D6 is LOW when Write ENABLE and HIGH when Write Protected.

The uSD socket I selected for the UBW32-MCC only had one switch for card present so I linked both D5 and D6 together as uSD cards dont have a WP switch. You can safely just short D5 and D6 to GND but I dont know what the MM would do if there is no card inserted.

Regards,

Mick

Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<

MOBI
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Joined: 02/12/2012
Location: Australia
Posts: 819

Posted: 12:52am 07 Mar 2013

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@Mick,

Yes, that fits the situation here.

I've wired up the SD card holder per MM schematic. If I have D5 (card present) high, "files" command says "error: SD card not found". If D5 is low, it obviously detects the card.

It doesn't matter which way I set D6 (write protect), it says "error: cannot access the SD card"

I wonder, are there any critical parameters here? e.g. is R17 critical @ 2.2ohms? I don't have a 2.2, so I tried 3.9 and also 2x1ohm in series. Same result.

Could the flying leads be too long at 8" ? Perhaps the clock doesn't like long leads?

Any thoughts or experience?

David M.

MOBI
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Joined: 02/12/2012
Location: Australia
Posts: 819

Posted: 01:32am 07 Mar 2013

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@mick

I think the only thing critical here is my mental capacity and eyesight.

I'm almost too embarrased to say that there was nothing really wrong except.....I wired the SD holder onto a bit of pre used vero board with a convenient 9 pin header. All the wires to the right pins but unfortunately I had cut a strip across the vero board for isolations purposes in the previous use of the vero. My eyesight not quite good enough to see it but I should have. I could have kicked myself - all evening stuffing around double checking every thing for a b...y air gap (7 of them!)

How often does one do that sort of thing?

At least I know that the MM will tolerate long flying leads and still work.

David M.

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