micro SD. are serial resisters important?

mctrivia

I am redesigning my propmod-us_ps_sd to make assembly easier and would like to remove the series resisters between the prop and the uSD card since this is a point were i get lots of failures(lifted traces, or shorts). Are there any reasons not to remove this?

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Leon

Why does it need series resistors? I don't use any with my adapter.

Leon

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mctrivia

I see no reason that they are needed. They are in the schematic in the FSRW code so I included in original PCB. Now I want to remove but before I make design change I am asking the forum if there are any reasonable objections.

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rokicki

They are only in the schematic for the slow spin code, as a precaution.

You definitely do not want them with the high speed code.

Cluso99

No serial resistors required. However, it is a good idea to have 10K pullups on the 4 interface lines.

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Leon

I only used one pullup- on CSn. If that is pulled up I don't think it matters what else is going on on the other lines.

Leon

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Rayman

I don't use any pullups and haven't had a problem...

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Cluso99

See the Dracblade thread. He is having problems without the DO pullup.

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Links to other interesting threads:

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Leon

That's very strange. Something else must be going on.

Leon

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Rayman

An early version of FSRW2 had an issue without pullups, but that was fixed...

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mctrivia

well I will definitely include pull up resisters. They are not a source of trouble for me and it is better to have then to want.

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Dr_Acula

Re "An early version of FSRW2 had an issue without pullups, but that was fixed..."

That could be a clue, as I think the fsrw that is needing pullups might be from nearly a year ago. Certainly the latest download seems quite different. I might drop the latest code in and see what happens...

Leon and Rayman, which code are you using - "' fsrw 2.6 Copyright 2009 Tomas Rokicki and Jonathan Dummer " or something else?

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Post Edited (Dr_Acula) : 12/24/2009 2:27:50 PM GMT

Leon

I used the fsrw23 software:

http://forums.parallax.com/showthread.php?p=862944

Perhaps I should try it with the latest software, to see if there is a problem.

Leon

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Post Edited (Leon) : 12/24/2009 3:15:31 PM GMT

Leon

I just tried the fsrw 2.6 software, it worked OK.

Leon

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Kye

As mandated by the sd card spec you should use pull up resistors or the card will suffer from increased power consumption.

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Nyamekye,

Leon

I think that will only happen if the card inputs are left floating. Once the Propeller is running the application the card inputs should have well-defined logic levels.

Leon

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Kye

D1 and D2 for the SD card are not connected normally for SPI communication. They need to be pulled up.

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Nyamekye,

Rayman

Leon said...
I think that will only happen if the card inputs are left floating. Once the Propeller is running the application the card inputs should have well-defined logic levels.

I agree with this.· I don't believe that increased power consumption argument.· It's only a floating input to the SD card that could cause a problem.

Bean told me that all new SD cards include internal pullups.

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Leon

I'll check mine and see if that is true.

Leon

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Cluso99

Kye: IIRC the spec recommends D1 & D2 be pulled high, although I have not seen many (any?) circuits that do this. I do not do this and we have no problems. I do however have pullups on the other pins (DI, DO, CLK, -CS). I specifically require -CS to be pulled high as I tristate this pins (and the others).

However, it should be mandatory that -CS be pulled high unless the card has internal pullups. This is because at least this pin will be floating until the prop runs code making this an output. This should alleviate any issues of other pins not being pulled high as the chip is disabled.

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Links to other interesting threads:

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· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

AP

And.... SPI mode is only optionally available on micro-SD. It might not be available on whatever specific card you are trying to use. SPI mode is "always" available in mini and standard SD

rokicki

Has anyone found a microSD card that *doesn't* support SPI?

I think these will simply be vanishingly rare; I can't imagine they have separate controller chips for
SD/miniSD/microSD, especially since the adapters between these versions are just passive wire
adapters.

I think pullups on floating CMOS inputs are always a good idea (even on the prop) but maybe
that's just old-school. Perhaps the current consumed by a bouncing input these days is such a
small fraction of the total chip current that it's negligible.

Internal pullups on the SD card just make sense, though; eliminating discretes eliminates points
of failure.

Cluso99

I would actually be surprised these days if there is not internal pullups in the SD/uSD controller chips. However, I believe it is good practice to put them on the SPI pins.

I have not found any uSD cards not supporting SPI. However, I only use SanDisk. uSD and passive adapters are becoming the norm, even to other formats such as XD?? on Olympus cameras (they now come with an adapter and uSD card).

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)·
· Prop OS: SphinxOS·, PropDos , PropCmd··· Search the Propeller forums·(uses advanced Google search)
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mctrivia

i only use san disk also but I have not found any that do not work.

micro sd really was the only option. I had to shave 2mil off the recommended footprint to squeeze a micro sd card slot onto my propmodules.

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Cluso99

I have a 1GB SanDisk (came with my USB mobile internet device - it has a uSD socket that can be used for a USB drive also). It does not work properly under some circumstances. Not sure why. It is the only 1GB that I have. I have used a number of 2GB SanDisk without problems. I do not buy from eBay.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)·
· Prop OS: SphinxOS·, PropDos , PropCmd··· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBlade Props: www.cluso.bluemagic.biz