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Paul_L
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Posted: 13 July 2018 at 9:48am | IP Logged Quote Paul_L

lizby wrote:
Here's the output from running on a Pi Zero W.
Write to file is a good bit slower than any of the others, perhaps for the reason Peter gave for the Nucleo. Others are generally a bit faster than the MM+ at 120mHz.

The SD card is (nominally, at least) a SanDisk Ultra 16gb class 10.

Hi Lance, actually the Pi is a tiny shade faster than the MMX in writing the file.


                 ms       MB/sec
i5@5GHz        2891        15.91
Cel@2GHz       8203         5.61
MMX@252      189127         0.24
MMX@200      189466         0.24
MM+@120      325843         0.14
MM+@100      365102         0.13
nucleo       566168         0.08
pi-zw        207839         0.22

The Pi sounds interesting but .... it requires an operating system which reduces the stand alone run forever suitability, doesn't have many general I/O ports, and it's so darned small I'll probably break the darned thing. It's unfortunate because Ada (Limor "Ladyada" Fried) located her business, Adafruit, about 75 miles south of me in NYC when she left MIT and it would be an ideal parts supplier for me. I think I'll stick with the MMX.

Paul in NY




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chronic
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Posted: 13 July 2018 at 9:53am | IP Logged Quote chronic

It is worth remembering, the useage of SD cards is different on micros wrt PCs etc.
A micro typically uses a sd card for logging / limited power and it is best for the software to at least close a file, and maybe power-off the sdcard between accesses, as often as realistic. Restarting it and opening a file takes a long time, but saves your data, particularly in unknown timeframes etc. Using a sd card on a PC on the other hand is usually always-on with ongoing access so software is usually optimised for that.

ed- by PC I mean Pi's etc , things with OS's

Edited by chronic on 13 July 2018 at 9:58am
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Paul_L
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Posted: 13 July 2018 at 11:35am | IP Logged Quote Paul_L

@chronic - I agree that you should close files on an SD card when you're not actually writing to them, but how do you power-off the SD card with a PIC based MMBasic program?

Paul in NY
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chronic
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Posted: 13 July 2018 at 9:52pm | IP Logged Quote chronic


Quote:
how do you power-off the SD card with a PIC based MMBasic program?


For the pic/MMbasic kits, it might take a hardware mod to allow the power to the sdcard to be switched under software, maybe associated software mods too. So
I'll throw that open to the MMBasic gurus, it is probably worth a different thread if the answer involves much.
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Paul_L
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Posted: 14 July 2018 at 10:23am | IP Logged Quote Paul_L

Hey Stuart, why would you want to cut power to an SD card when all files are clsoed anyway?
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chronic
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Posted: 14 July 2018 at 11:44am | IP Logged Quote chronic

I am not using the pic/MMbasic for it, (pic/MMBasic is probably more reliable than what I am doing), but in general I have found that a card hard power reset just before access is more reliable (particularly for writing records) than to leave the sdcard powered on for a long time (say an hour) between use. A card soft reset doesn't seem to be as reliable. My impression is, some RF noise on the leads can glitch the card state after a while and it doesn't reset well - thats just a guess at this stage. Pity because it makes the overall process quite slow.
There are other factors which make it useful as well, but they are probably irrelevant to most people so I'll leave them out here.
I guess it would would save a little power too, if access is only infrequent.
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