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MicroSD memory card tester

phanick 5166 13
This content has been translated flag-pl » flag-en View the original version here.
  • MicroSD memory card tester
    In this article, I will describe the reason for inventing and designing a tester for microSD memory cards, which will be used to check some interesting properties of cards.

    Cause of the uprising
    MMC / SD / microSD cards, apart from their natural applications, are also liked by fans of microcontrollers for several reasons:
    * can be used as an additional memory with a really large capacity (both for reading, e.g. when displaying photos when the microcontroller controls the digital image frame, and for saving e.g. measurement results from a thermometer
    * simplify the exchange of this data with a PC or telephone
    * communicate with the outside world either using the SD or SPI protocol (the latter is extremely easy to implement)

    At the beginning, there were MMC cards (up to 128MB, I think), later they were replaced by SD cards (identical in size), and then mini and micro SD cards were created. There were "regular", "SDHC" and "SDXC" cards. Detecting the type of card (and thus the way of addressing it) can be difficult. This is perfectly described in the article below:
    http://elm-chan.org/docs/mmc/mmc_e.html

    and this is perfectly illustrated by the diagram below:
    MicroSD memory card tester

    The SPI protocol is a serial full-duplex data transmission protocol in which:
    * on the MISO (Master Input Slave Output) line, the data goes from the card to the host (e.g. PC),
    * on the MOSI line (mater Output Slave Input, the data goes from the host to the card.
    * and all this happens in time with the SCLK clock signal generated by the host.
    * there is also a fourth line (nCS) which ... that's it

    Theoretically, it is to enable the connection of several cards to one host using the same MISO / MOSI / SCLK lines. Each card would have its own separate nCS signal that would be active while transmitting with it:
    Code:
                                     
    
                                           VCC VCC   
                                            |   |
    SCLK ---+----------+----------+         R   R
    MISO ---|+---------|+---------|+--------+   |
    SCLK ---||+--------||+--------||+-----------+
            |||        |||        |||
         +-------+  +-------+  +-------+
         |Karta 1|  |Karta 2|  |Karta 3|
          +-------+  +-------+  +-------+
             |           |          |
    nCS1-----+           |          |
    nCS2-----------------+          |
    nCS3----------------------------+


    In practice, however, hardly anyone uses it and most often we deal with a single card. So what about the nCS line? Theoretically, it should be low (active) only during the transmission of 8 bits, then go high (which would signal the transmission of the entire byte)
    Code:

    SCLK __--__--__--__--__--__--__--__--________--__--__--__--__--__--__--__--______
    MISO ------------
    nCS  --______________________________--------______________________________------


    In practice, however, this line may be in a low state all the time and the card does not make any difference (and our microcontroller then has one more pin for other needs). Are you sure?

    Well, according to the above-mentioned diagram, just after applying power to the card, one should wait a moment and send it at least 74 clock cycles to "start up". During these warm-up cycles the nCS line should be inactive, and then after "warming up" to shutdown it may be low. And by doing so, I was able to communicate with each card without any problem.

    However, in a device that I once designed, the nCS line was permanently grounded (saving pins and resources). It worked on the card I had at the time. Then I bought a dozen other cards and it turned out that some "do not want to communicate". It was bad news, because I already had more boards to build the device on my desk - reworking would become cumbersome (so it was not an option). I tried to find some rule - e.g. Sandisk cards always worked, and other producers or even no-name sometimes had whims). I wanted some kind of 100% effective method of determining that would allow me to find out before buying the card, preferably by its appearance alone. Well, cards like these cards, after the manufacturer's logo are the same after all. However, not really - I discovered an interesting property:

    MicroSD memory card tester

    The cards on the left (operating with the nCS line always on the ground) are "smooth" on the back (either all black or with some inscriptions), and the ones on the right (capricious) have either a sticker or some strange contact areas. Always when buying cards, I asked the seller to choose "smooth". However, because I was not sure if it was a 100% effective method, I decided to create a simple device-tester with: a card slot, a button and two LEDs that, after pressing the button, perform a check and light up depending on whether the card is OK or capricious . I wanted to send the device to the seller before buying it.

    Design
    In order to cut costs, the device will be based on a miniature Attiny13 microcontroller. He only has 8 legs. By subtracting VCC, GND and / RESET - there are 5 pins left for your own use:
    - the program is so simple that it does not require any interaction from the user (so the test button can be connected to the / RESET pin)
    - two LEDs, cleverly connected to select one of the three states (0/1 / Z) which of the LEDs (respectively: red / green / none) should light up,
    - MMC / SD cards require 3.3V power supply, so a stabilizer will be useful,
    - and a circuit 74LVC245 for converting the voltage levels on the lines going to the card (MOSI / SCK / nCS); MISO (outgoing from the card does not require conversion)
    - the microcontrollers I have (ATTINY13V) can be powered from as low as 3.3V, so the 74LVC245 converter would be redundant, but ... the USBASP programmer I use is powered from 5V and this is also the level of signals on the lines used during programming, so it could damage the attiny 'ego.
    - card slot and mini USB socket for power supply
    MicroSD memory card tester MicroSD memory card tester

    The tile, as usual, was quite nice:
    MicroSD memory card tester MicroSD memory card tester



    Software
    In attiny, we only have 1024 bytes per code, so don't go crazy. The program performs 2 identical tests one after the other:
    * TEST1 - attempt to communicate with the nCS card constantly on the ground
    * TEST2 - setting the nCS to a high state, launching 80 warm-up cycles, returning the nCS to ground and trying to communicate

    Each of the tests:
    * or it will fail,
    * or we manage to communicate with the card - then it determines which card we are dealing with.

    Code:

    Wyświetlanie wyniku testu:
    dioda   | dioda    | wynik
    zielona | czerwona |
    --------+----------+-------
       -    |   miga   |  TEST1 fail, TEST2 fail (błąd komunikacji)
    miga (*)| miga (*) |  TEST1 fail, TEST2 pass (karta kapryśna)
    miga (*)|     -    |  TEST1 pass, TEST2 pass (karta ugodowa)

    (*) - ilość mignięć oznacza:
    1 -> karta SD VER.2 (block address)
    2 -> karta SD VER.2 (byte address)
    3 -> karta SD VER.1
    4 -> MMC VER.3


    From the cards I have:
    * 4GB and 2GB cards are SD VER.2 (byte address)
    * a card with a capacity of 32GB is SD VER.2 (block address) - no wonder, because on 4 bytes (32 bits) you can address a maximum of 4GB


    The presentation


    Kod
    [syntax=C]
    #include // Most basic include files
    #include // Add the necessary ones

    #include
    #include
    #include "e:\Pulpit\projekty\elektronika\Atmega - mikrokontrolery\!programy\prog-c\misc2.h"

    #define CMD0 (0x40 | 0)
    #define CMD1 (0x40 | 1)
    #define CMD8 (0x40 | 8)
    #define CMD16 (0x40 | 16)
    #define CMD17 (0x40 | 17)
    #define CMD24 (0x40 | 24)
    #define CMD58 (0x40 | 58)
    #define CMD41 (0x40 | 41)
    #define CMD55 (0x40 | 55)

    #define SPI_MOSI B0
    #define SPI_MISO B1
    #define SPI_SCLK B2
    #define SPI_nCS B3
    #define LED B4

    void led_green() {
    as_output(LED);
    out(LED, 1);
    }

    void led_red() {
    as_output(LED);
    out(LED, 0);
    }

    void led_off() {
    as_input(LED, PULLUP_OFF);
    }

    #define DELAY1 200
    #define DELAY2 800
    // makes blinks of red/green/both diodes (waits DELAY1 after each blink) and then wits DELAY2
    void led_blink(bool is_red_on, bool is_green_on, uint8_t count) {
    for (uint8_t i = 0; i < count; ++i) {
    for (uint8_t j = 0; j < 100; ++j) {
    //red and green cannot be turned on at once but turning one
    //and then the other very fast makes illusion that both are turned at the same time
    if (is_red_on && ((j & 1) == 0)) {
    led_red();
    }
    if (is_green_on && ((j & 1) == 1)) {
    led_green();
    }
    _delay_ms(DELAY1 / 100);
    }

    led_off();
    _delay_ms(DELAY1);
    }
    _delay_ms(DELAY2);
    }

    //sends 8 bits (data) on MOSI
    //receives (and returns) 8 bits on MISO
    uint8_t mmc_transfer_byte(uint8_t data, bool enabled) {
    uint8_t result = 0;

    for (int i = 7; i >= 0; --i) {
    out(SPI_MOSI, (data >> i) & 1);
    out(SPI_SCLK, 1);
    result |= (in(SPI_MISO)

    Cool? Ranking DIY
    Can you write similar article? Send message to me and you will get SD card 64GB.
    About Author
    phanick
    Level 28  
    Offline 
    phanick wrote 2446 posts with rating 2533, helped 56 times. Live in city Warszawa. Been with us since 2007 year.
  • #2
    LA72
    Level 40  
    And to think that the good little toddler ATtiny13 can get away with it.
    Way to go.

    Have you ever tested some "fake" card? (false capacity)
  • #3
    spec220
    Level 25  
    A very interesting project, a quick test of memory cards.
    However, personally, I think that tiny13 is a bit unsuitable for this, although I must admit that the article itself certainly presents / presents my colleague's skills and programming skills.

    Personally, I bought a simple gadget for a few pennies that allows full access to SD cards and memory.

    MicroSD memory card tester
  • #4
    krzbor
    Level 23  
    phanick wrote:
    Theoretically, it is to enable the connection of several cards to one host using the same MISO / MOSI / SCLK lines. Each card would have its own separate nCS signal that would be active while transmitting with it:

    It's a bit wrong - SPI is not only used to connect cards - it is very often used to work with displays, ADC / DAC converters, RTC clocks, etc. The nCS signal should, in principle, be properly connected.
  • #5
    Eidems
    Level 29  
    @phanick, are you buying used memory cards? It happened to me several times that the microsd card stopped working by itself. That is why I replace my telephones as a preventive measure every 2/3 years. The cost of such a card is ridiculous.
  • #6
    ZnAl
    Level 14  
    A very interesting project. :spoko:

    I just have a small note on this part of the description:
    Quote:
    there were MMC cards (up to 128MB, I think), later they were replaced by SD cards (identical in size)

    Not all dimensions are the same.
    MMC cards (full size) are 1.4 mm thick as standard, while regular SD cards are 2.1 mm thick.
    There are devices that only MMC cards can fit, and SD cards cannot.
  • #7
    bsw
    Level 18  
    phanick wrote:
    - the microcontrollers I have (ATTINY13V) can be powered even from 3.3V, so the 74LVC245 converter would be redundant, but ... the USBASP programmer I use is powered from 5V and this is also the level of signals on the lines used during programming, so it could damage the attiny 'ego.

    From my experience, I know that the microcontroller will not damage, but may damage other accessories that work with it.
    There is a solution for this - a simple modification of the USBASP programmer or an adapter for the USB port that lowers its voltage:

    https://e-bsw.blogspot.com/2017/09/usbasp.html

    Added after 23 [minutes]:

    ZnAl wrote:

    Quote:
    there were MMC cards (up to 128MB, I think), later they were replaced by SD cards (identical in size)

    Not all dimensions are the same.
    MMC cards (full size) are 1.4 mm thick as standard, while regular SD cards are 2.1 mm thick.
    There are devices that only MMC cards can fit, and SD cards cannot.

    MMC cards existed up to 512 MB. There were also devices in which the SD could physically fit, but it was not supported - only MMC.
    In addition to the difference in thickness and the lack of a write-protect switch, the MMC cards also had additional contacts:
    MicroSD memory card tester
  • #8
    zgierzman
    Level 30  
    bsw wrote:
    MMC cards existed up to 512 MB. There were also devices in which the SD was physically located but it was not supported - only MMC.
    In addition to the difference in thickness and the lack of a write-protect switch, the MMC cards also had additional contacts:


    Those were strange times, there were also MMC "half length" (half length) and there were several, if not a dozen other standards. Each manufacturer is a different card. And this is the Memorty Stick, and this is a different invention. As with connectors for charging phones. Fortunately, it somehow straightened. :-)
    MicroSD memory card tester
  • #9
    Sentymentalny
    Level 10  
    Is it not possible to add the misc2.h file to the set?
  • #10
    phanick
    Level 28  
    Thanks for your interest in the topic.

    LA72 wrote:
    And to think that the good little toddler ATtiny13 can get away with it.
    Way to go.

    Have you tested some "fake" card? (false capacity)

    I don't have one (or I don't know anything about it). I understand that the card then returns a different capacity than the physical one, and the partition also overlaps this enlarged part. I have to be interested in this, because I wonder if the system tries to save something there, the data is not saved anywhere, or maybe they overwrite other data in the real area?

    However, I have one memory card, which is not detected by the system at all, but the tester is testing it successfully. Maybe access to data is blocked in it, or the memory bone has been damaged, but the controller is working?

    Eidems wrote:
    Are @ phanick you buying used memory cards? It happened to me several times that the microsd card stopped working by itself. That is why I replace my telephones as a preventive measure every 2/3 years. The cost of such a card is ridiculous.

    In my application, the cards do not store critical data and are mainly used as a data store that the device then reads from. Maybe you have had a physical damage to the card (e.g. a microcrack)?

    spec220 wrote:
    Hello, a very interesting project. Quick test of memory cards.
    However, personally, I think that tiny13 is a bit unsuitable for this, although I must admit that the article itself certainly presents / presents my colleague's skills and programming skills.

    Personally, I bought a simple gadget for a few pennies that allows full access to SD cards and memory.

    In the current application, it is on the contact (about 87% of the memory is used), but if you wanted to, for example, make it a full-fledged diagnoser, which also allows you to read / write data to the card and communicate with the PC via USB (and not only power supply), then mega8 would be minimum.

    In addition, the USB reader uses the latter communication protocol with the card, so my problematic cards are indistinguishable for him from non-problematic ones.

    Quote:
    Is it not possible to add the misc2.h file to the set?

    I added
  • #11
    tmf
    Moderator of Microcontroller designs
    phanick wrote:
    In practice, however, this line may be in a low state all the time and the card does not make any difference (and our microcontroller then has one more pin for other needs). Are you sure?

    CS is also used to synchronize operations on the SPI. Think what will happen if the CS is constantly active and there is a disturbance on the SCK? The transmission will be unsynchronized and only some internal timeouts from the card can restore proper communication. So it's better to do it right, that is, connect the CS and change its state to active only for the time of transmission.
  • #12
    eurotips
    Level 38  
    If you are sitting in the topic, come up with a device for changing the CID of the card.
  • #13
    Błękitny
    Level 13  
    You can also make such a system for reading card parameters:
    Link
    Link
    i built this device and it works very well.

    When it comes to changing the CID number, they fought here:
    Link
  • #14
    funzen
    Level 17  
    MMC cards are larger than 512 MB, I have a 2 GB MMC card myself.
    MicroSD memory card tester