Micro SD extender cable

Other Hardware Storage
1

This question relates to the Arduino Antenna Analyzer (AA) and
the use of an Lanmu 5.9 inch micro SD extender cable.

A number of us built the AA and have been using them regularly.
One thing I/We would like to do is keep historical traces of a
given antenna to see if there are changes or potential problems.
This means being able to take the scan files off the SD card and
importing them into Excel for each antenna which is pretty easy.
With the AA once it is in a case this is not practical so I
purchased a 5.9 inch micro SD card extender cable and ported it
outside the AA case. The problem is the AA no longer recognizes
that there is an SD card present. This problem seems to crop up
in other Arduino projects.

The project is built on an Arduino Mega 2560 Pro Mini, an analyzer shield and a MCUFriend 3.5 inch LCD display with a micro SD card socket. The sketch uses the regular SD and
MCUFriend libraries.

Looking at what I understand of the AA sketch and libraries it
appears the test for a card present is to write a short text file
and save it. If there is more it is beyond me.

As a start I'll say with the card plugged into the display it
is recognized and saves scans. I've looked at some of the
libraries like SD.begin and other SD.XX and gleaned no other info.

I have tried three different extension cables in the six inch
length and three different SD cards.

I can take any of the extenders and SD cards to several different
laptops and read and write to them. The issue has also been
replicated by another person with an AA and computers.

I tried another MCUFriend display and it has the same issue, the
SD card works in the display but not in the extender. I tried
mounting the SD card from the maintenance menu in the sketch and it fails the same way (card not present).

I physically measured the SD card and psuedo SD card on the
extender and they are nearly the same. I watched what I believe
is the card detect switch in the SD card socket on the display
and there is no visible difference, under magnification, between
them as the card is inserted. Since the original card present
switch is activated by the extender there shouldn't be an issue
there.

These extenders come in lengths up to 27 inches that I have
seen, so I wouldn't think a six inch extender would exceed
any limitations that might affect timing.

My understanding is the display shield just passes through
the SPI lines from the Arduino to the micro SD socket so the
problem seems to lie in the Arduino or SD libraries and how
they sense a card present.

I did some internet searches and this seems to be a common issue whether for cameras, 3D printers, regular printers, GPS's, Rasperry Pi's. Is is that the drivers for these devices are that much different or poorer than a regular Win10 computer?

Is there a way to make this work?

Stan

2

Unless the extender is faulty, that appears to be exactly what is happening.

The Mega is a 5V logic level device and the SD card and display is 3.3V logic so the display has a logic level converter on it.

Maybe the logic level converter on the display for the SD card is sensitive to long cables ?

Check whats happening to the SPI signals on the SD card with an oscilloscope.

3

On the micro SD extender problem the three extenders I have were tested on three different laptops, with three different micro SD cards and worked properly. They only don't work on the MCUFriend display, though the SD card works fine directly. I have some micro SD breakout boards coming to do some electrical tests.