SPI SDcard module question

barryfields · October 20, 2025, 12:57am

I went to order an SPI SD card module and found the attached comment.

Does it make sense?

sonofcy · October 20, 2025, 1:16am

If you are not accustomed to using hot air guns on very small components I would advise against it as you can easiy destroy the board.
Find a board that is designed to work in a multi device SPI environment.

barryfields · October 20, 2025, 1:38am

I need to know if the modification makes sense.

As far as technique, I got this.

gilhad · October 20, 2025, 1:58am

It does make sense.

The module is produced so it will send signals to MISO regardless if it is selected or not. So if you have 2 or more SPI components connected, it will destroy the communication for any other component.

(The usual - I have SPI SD card and SPI something and it does not work. Many Arduino beginers had this problem.)

This technique make the output of MISO pin HiZ if the SD Card is not selected.

I do something similar with my SD cards - I desoldered the chip, cut two traces, resoldered it and soldered wire to CS pin:

github.com/githubgilhad/MegaHomeFORTH

HW/Foto/SD_card/SD_card.rst

master

.. vim: set ft=rst showbreak=»\  noexpandtab fileencoding=utf-8 nomodified   wrap textwidth=0 foldmethod=marker foldmarker={{{,}}} foldcolumn=4 ruler showcmd lcs=tab\:|- list tabstop=8 noexpandtab nosmarttab softtabstop=0 shiftwidth=0 linebreak  

SD_card
========

The same as in `Expanduino <http://8bit.gilhad.cz/6809/Expanduino/Expanduino_I.html#sd-karta>`_

I bought some cheap cards from china, with 74HC125 level convertor. basically it is `this type <https://www.hwkitchen.cz/modul-ctecka-micro-sd-sdhc-karet/>`_. 

This cards are known to have problem with `SPI`:

* It does not 3state `MISO` when not selected and so it conflicts with other projects on `SPI`. 
* May also ignore `CS` for `Data In`
* Also it require to have `CS` set to 0 when card is to be insert, and on powerup to set the card to `SPI` compatible mode.
* The solution is to modify this card as in `SOLVED. Nrf24 (Mirf lib) + Micro SD-card works OK together <https://forum.arduino.cc/t/solved-nrf24-mirf-lib-micro-sd-card-works-ok-together/347787/3>`_
* My card cannot be just cut as in the article, because the ground goes there also from the chip - see photos - so I will disconnect it at both places and connect it to `CS` - also it can be done by lifting that leg and soldering wire on it.
* Also it may be done from outside, with some other gates, as in  `Expanduino <http://8bit.gilhad.cz/6809/Expanduino/Expanduino_I.html#sd-karta>`_ Expanduino_I_fix_001_schema.png
* and on next iteration I may just strip the parts and incorporate it into PCB with all `enable` pins (except the for `CS`) connected to `CS` on the PCB

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barryfields · October 20, 2025, 2:04am

Many thanks

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SPI SDcard module question

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