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Most CF Cards Fail DMA Transfers
Posted by
kdawson
on Sat Jul 12, 2008 03:28 PM
from the it's-all-in-the-controller dept.
from the it's-all-in-the-controller dept.
Anomalyst writes "In his quest to create an open source video camera, Andrey Filippov of elphel.com has determined that most Compact Flash devices, although claiming to be DMA capable, do not perform Direct Memory Access transfers correctly. This means successful movement of data to and from the device takes much more time with DMA disabled." The culprit appears to be the controller chip packaged with most of the CF cards Filippov tried. We last visited Elphel and their work on open source digital cameras in 2002. Filippov gave a Tech Talk at Google last year.
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Embedded Linux On a High Speed Camera 91 comments
destructor writes: "Linuxdevices has an interesting article on a High Speed Gated Intensified Camera that
"combines a fast gated micro-channel plate (MCP) image intensifier, a CMOS image sensor, and an embedded computer based on an Axis Communications ETRAX RISC processor running Embedded Linux." The camera (Elphel Model 303) itself is network operable and can be used for capturing images of explosions, lightning bolts, etc. Link found via. megarad.com."
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Creative (Score:4, Insightful)
Re:Creative (Score:4, Informative)
It's pretty fascinating how the company that appears to be the market leader is also the worst in terms of actually delivering a good sound card. Then again, maybe it shouldn't surprise me since they're also the biggest liars. I got bitten twice.
NEVER AGAIN
Parent
Re: (Score:3, Informative)
Re: (Score:3, Interesting)
It's like the difference between an onboard video setup and a "real" one. People who need more features always have to pay a little more for them.
Re:Market leader? (Score:5, Funny)
I upgraded from onboard audio to an X-Fi Fatal1ty. My Kill to Death ratio went up by about 25% within a few days.
NEVER underestimate the power of.... Celebrity Endorsement !
Get the Fatal1ty mousepad to go up another percent.
Parent
Lexar and Sandisk should be good (Score:4, Informative)
Re:Lexar and Sandisk should be good (Score:5, Interesting)
How do you know that it indeed works in a full-fledged UDMA mode and not in some half-assed workaround mode, used specifically because of the problems in question existing in the cards' controllers. Did you reverse engineer the camera's firmware?
Parent
Re:Lexar and Sandisk should be good (Score:5, Insightful)
Also, the article said that the Sandisk card they tried worked. They did not mention anything about Lexar but did mention problems with Transcend, which is not certified for my camera.
Parent
Re: (Score:3, Informative)
I can't vouch for cameras, but I created a CF-based hard drive to boot my Windows XP tablet PC using one of these [addonics.com]. It has two CF slots, and my tablet's IDE controller supports UDMA. In Windows, you can check what UDMA/PIO mode your disks are in by clicking the Advanced Settings tab on the IDE adapter's property page in Device Manager.
The first device I tried was the cheapest UDMA CF card I could get my hands on (233x 16gb Ritek), and after a few disk driver errors, it dropped out of UDMA mode and the laptop
Try Transcend, but watch for voltage (Score:3, Informative)
Like the previous poster, I use a Transcend CF card to run XP and Ubuntu on a laptop. I recently "upgraded" to the 16GB 300x version, since it was supposed to run at UDMA5. I wrote the review here [newegg.com].
Short story: According to Transcend, the card has to run at 3.3V in order to run in UDMA5 mode. I'm also using that Addonics 2-card CF-to-IDE adapter, and it doesn't offer voltage choices, so I'm stuck at 5V and the slower speeds -- au
From the utterly irrelevant department (Score:3, Funny)
What's next, some USB mice fail at implementing the USB 2.0 standard? Or some random printer which claims to support PCL really doesn't?
Geesh, talk about a slow news day.
SanDisk cards are usually a safe bet. (Score:4, Interesting)
I can vouch from personal experience with their engineers that their cards rated for 30MB/s or higher all support UDMA 4 or higher, and I've done tests of my own to verify this. Not all ExtremeIII cards support UDMA though; the ones that don't specify a speed of 30MB/s are instead rated for 20MB/s, which can be quite easily achieved using PIO6 (although less efficiently.) These cards might support UDMA, but since there's no *need* for it, there are no guarantees.
Also, I'm pretty sure Lexar cards rated for UDMA do perform as advertised. I can't vouch for other manufacturers. Additionally, be wary of fake cards (ebay is especially prone to fake card sales) as they're never going to perform to your expectations.
Re: (Score:3, Informative)
IDE Compatibility Issues (Score:5, Informative)
As far as I can tell (without a bus analyzer,) there's something hinky happening during device auto-detection and initialization. Many times, the CF card will be detected as the Master device, but no Slave device will be detected. Swap to a different brand CF card, and the symptom will change - both devices will auto-detect, but the IDE bus will throw timeout errors during boot. Swapping in just about any not-a-CF-card device, and everything is fine.
Re:IDE Compatibility Issues (Score:4, Insightful)
A while ago I built my mythtv frontend, (based off a T-Online vision s100 box) and elected to use a CF card for storage within the unit - the box is entirely free of moving parts, so CF made sense.
I bought one of those IDE to CF adapters off ebay, and found that when I turned on DMA, the IDE bus would basically lock up, and pretty much end up useless.
After a lot of fiddling and digging around, I discovered that the adapter did not connect the required pins for DMA transfers to work. Old-skool CF never had DMA, so this extra pin is only a recent addition to the standard.
Anyway, I soldered in a short wire to hook up this pin, and now I get respectable dma transfers.
The moral of the story - it might not be the CF card that is causing DMA failure, but the adapter it's hooked into.
Parent
CF inside the cameras do not use "True IDE" mode (Score:5, Informative)
Re: (Score:2)
I guess FTP isnt good enough for you?
Re: (Score:3, Insightful)
Re:Good work (Score:4, Informative)
I think the OP was tricked into thinking that the crappy software that came with the camera was actually required to use the camera. The instructions that come with these cameras do tend to make it sound like installing the software is a mandatory step, and fail to mention that you can just access the pictures using Explorer. I guess they want to get their little bit of AdWare on your system. Or maybe they really are worried that Aunt Tillie doesn't know how to use Explorer.
Parent
Re: (Score:2)
Just about every camera I've looked at recently has a bog standard mini-USB connector and didn't require custom software to see the camera's contents as a drive, at least not with OSX.
Re: (Score:3, Informative)
"disclaimer: only tested on OS X, not tested on animals, no DLLs were harmed in the making of this message, age 45 and older excluded, milage may vary depending on driving conditions, poster assumes slashdot readers are capable of understanding the concept of 'context', emoticons are optional and may require a surcharge."
Re: (Score:3, Informative)
Compact flash is/was the standard on the high end. SD is making some inroads, but for a long time, fancy cameras had CF slots and that was your choice.
Re:Compact Flash (Score:5, Informative)
Parent
Re:Compact Flash (Score:5, Informative)
Parent
Re: (Score:3, Interesting)
Elphel would put some $50K in the pool (if there was one) to buy a serious PCB CAD software no make it GPL-ed.