43
votes
Accepted
MicroSD card performance deteriorates after long-term read-only usage
Hm, my usual suspicion would be that your read access goes through a file system and that updates something, e.g. a file access time, in the file system, but that doesn't seem to be the case here.
...
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29
votes
Accepted
How to make 1 bit permanent memory circuit?
The original electronic nonvolatile memory is based on ferrite cores. While it's relatively easy to magnetize such a core in one direction or the other to store a one or a zero, it takes some fairly ...
- 165k
21
votes
Accepted
How can I initialize/use SD cards with SPI?
General advice
SDUC (ultra capacity, > 2 TB) cards don't support SPI according to the specifications.
There are several libraries that significantly simplify accessing the SD card, using a proper ...
- 491
20
votes
Accepted
Anyone either read japanese or know about laying tracks for a micro SD card slot?
Google translate on your phone can do this:
Parts prohibited area (部品搭軾禁止エリア)
Pattern prohibited area (パターン禁止エリア)
Soldering prohibited area (半田付け禁止エリア)
- 21k
19
votes
Anyone either read japanese or know about laying tracks for a micro SD card slot?
Disclaimer: I am clueless about EE, but read Japanese well enough to look this up.
Black box: 部品搭載禁止エリア = "components/parts-loading prohibited area" (don't put stuff here, I assume).
Diagonal ...
- 291
16
votes
Accepted
How long can a micro SD card hold data without being powered?
If you want to use the data on an SD card, assume it lasts less than 10 years. (*)
If you don't want someone else to be able to read the data on an SD card, assume it lasts indefinitely.
If bits gets ...
- 143k
15
votes
Difference between 1-bit, 4-bit and 8-bit SDIO
There are two modes of communicating with an SD card: SD mode (sometimes incorrectly called SDIO), and SPI mode (Serial Peripheral Interface). (SDIO actually refers to a Secure Digital Input Output ...
- 47.1k
14
votes
Anyone either read japanese or know about laying tracks for a micro SD card slot?
In this micro-SD socket the spring contacts are located at the bottom of footprint, and during card insertion they may touch the PCB surface. Therefore there is a chance that PCB protective layer will ...
- 37.5k
11
votes
Logging multiple sensors data to SD card at same time: writing hangs up
Never, never, never put file I/O in an interrupt routine - unless it is the only routine to do file I/O. And then still don't do it!
An interrupt can interrupt anything: including file I/O. And ...
- 1,423
10
votes
Accepted
What does SWITCH pin do on a microSD connector?
Looking at the drawing, I would guess that DETECT and SWITCH are the two terminals of the switch which detects the presence of an SD-card. This allows for more flexibility in circuit design
- 8,450
9
votes
Accepted
What does it mean when components in schematics do not connect?
IC1 has six sections (A-F) although only 4 are used the circuit.
In general it is not allowed to leave inputs of CMOS devices unconnected so the two at the bottom show what to do with the inputs, ...
- 29.7k
8
votes
Is it possible to use an SD card without a file system?
You didn't mention which PIC you are using, but assuming it is one of the smaller ones such as the PIC16 then with it's limited RAM (99% of PIC16's have no more than 1K of RAM) it would be impossible ...
- 47.1k
8
votes
How to make 1 bit permanent memory circuit?
Make a circuit that flicks a mechanical switch eg. useless box. The circuit would need to be powered up to change/read state but it would keep it in between.
- 211
8
votes
Accepted
8GB SD cards intermittently overwriting data
are there known risks and common problems like this writing directly to the card and avoiding an FS? (like block alignment)
Generally no, using the card as a simple block device is perfectly safe. ...
- 3,775
8
votes
Potting microSD card inserted in slot with epoxy resin
I wouldn't recommend it.
So, here's my theory:
SD card contacting depends on spring contacts in the SD card holder.
If your potting compound creeps into the gap between SD card and holder contacts ...
- 79.1k
8
votes
Make an SD card installed on PCB readable through USB
The cheapest solution from a hardware point of view would be to use a MCU that includes a USB interface (there are a lot of them in the PIC32MK/MZ/MX ranges), and just make the MCU responsible for all ...
- 15.6k
8
votes
Accepted
What do OD and PP stand for in SD card frequency fOD and fPP?
They mean Open Drain and Push Pull.
Identification is done slowly in OD mode so all devices can be enumerated without one driving the bus into other direction than others.
Data transfers can then ...
- 92.3k
7
votes
Accepted
How about soldering microSD card directly to PCB?
I have soldered wires direct to an SD card before now (I needed an SD card connected in an emergency and had no suitable socket for it). It worked fine, but I certainly wouldn't choose it, or ...
- 55.5k
7
votes
What does it mean when components in schematics do not connect?
The nets that are named 'CLK', 'DO', etc. are connected, just the wires aren't drawn for the sake of clarity. Now, IC1E and IC1F that are not connected to anything are unused portions of IC1, which ...
- 39.8k
7
votes
Accepted
My For loop isn't exiting and I don't know why
In your code you have the following suspect line:
for (int loop_bit=7; ((loop_bit < 8)||(loop_bit < 254)); loop_bit--){
...
}
The key problem with this ...
- 57.6k
7
votes
Accepted
STM32F072 - Working with HAL and FatFS
I've finally manage to implement low-level drivers and they seem to work nicely.
I'm sharing source code of my implementation in case somebody else gets stuck at the same part that I was.
- 132
7
votes
microSD card, how many times can I write the same sector?
how many times I can write the same sector entirely
You can't.
The memory controller will employ internal wear levelling and you have no way to force it to write to a specific physical sector. If ...
- 3,775
6
votes
Accepted
SD Card Access Library
One way to access an SD card faster (up to 4x) than using the 1-bit serial SPI mode is to use the 4-bit parallel mode.
Unfortunately, this faster mode is proprietary to the SD Card Association. Just ...
- 47.1k
6
votes
How about soldering microSD card directly to PCB?
If you want the simplicity of an SD-compatible interface, you can get what is essentially an SD card on a chip:
http://www.samsung.com/global/business/semiconductor/product/flash-emmc/overview
- 6,057
6
votes
How to make 1 bit permanent memory circuit?
A simple solution would be a micro controller such as a PIC12F635 which is available in an 8-pin DIP or smaller, and has a built-in clock and brown-out reset circuit (the latter is important to ...
- 336k
6
votes
How to make 1 bit permanent memory circuit?
Pure electronics won't make a permamnent memory cell, but charge in a capacitor can approach it (will need regular refreshing). EEPROM/Flash memory extends this requirement to 10's of years, so for ...
- 47.9k
6
votes
How to make 1 bit permanent memory circuit?
A fuse. It might be annoying to replace often, so you could upgrade to a breaker.
6
votes
A Guaranteed Way to Corrupt SD Card
If the data is really important, you should use a modern checksumming CoW (copy-on-write) file system like btrfs or ZFS. A recent kernel+btrfs can do "raid" on a single device, storing the data twice ...
- 12.8k
Only top scored, non community-wiki answers of a minimum length are eligible