Hot answers tagged

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. ...
user avatar
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 ...
user avatar
  • 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 ...
user avatar
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)
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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
user avatar
  • 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, ...
user avatar
  • 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 ...
user avatar
  • 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.
user avatar
  • 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. ...
user avatar
  • 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 ...
user avatar
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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
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 ...
user avatar
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.
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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
user avatar
  • 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 ...
user avatar
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 ...
user avatar
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.
user avatar
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 ...
user avatar
  • 12.8k

Only top scored, non community-wiki answers of a minimum length are eligible