[fixed in 0.95 ?] preenfm3 sd card error

[Xavier]

Having the SD problem fixed is my highest priority now.
I cannot reproduce it with my SD cards so i would need to have your exact SD card reference so that i can buy it and try.
Thanks.

[Olivier]

I use this SDcard reader.
https://fr.aliexpress.com/item/32820320799.html?spm=a2g0s.9042311.0.0.27426c37lxLDpm

PM me your postale adress and I send you one, I live in France so you will get it very fast.

[Xavier]

I use this SDcard reader.
https://fr.aliexpress.com/item/32820320799.html?spm=a2g0s.9042311.0.0.27426c37lxLDpm

If it works with 0.90 and not with 0.91 i think it comes from the SDCard itself.
What model do you have ?

PM me your postale adress and I send you one, I live in France so you will get it very fast.

Thanks, that's not necessary for the moment 

[Xavier]

I just published a 0.92 firmware.
At the last moment i decreased the SD communication speed, would be great if you could give a try and let me know.
https://github.com/Ixox/preenfm3/releases

[Olivier]

I have try 0.92 firmware. The Outputs are OK.

My  SDcard reader works with a micoSd card Sandisk Mobile Ultra 8GB Class 6. It doesn't work with SD card Kingston 8GB class4. It also doesn't work with a very old SD card SimpleTech 128MB.

I have try the SDCard reader from the screen, the SDcard become hot very quickly and the screen was black or White, didn't remember.

[Xavier]

Seems like your SD card reader from the screen does not work.
I bought almost 10 from amazon between 10€ and 15€ they all worked well 

I still haven't found a SD card that does not work so i don't know how to debug that.

I'm glad you found a solution.

[Olivier]

Ili9341 TFT display's built-in SD card does not seem reliable (search on the internet). We are two with the same problem and need to use an external SDcard reader.
Another problem is about the dimension of this screen. Mine is shorter than the one you show on the Wiki/Build. This mean that it's impossible to fit a unique metal or 3D case.

Aliexpress or amazon are not reliable supplier for this screen. When we order a Ili9341 TFT, we do not get the same product.

The best case would be to define 1 reference for the screen and 1 reference for the  SD card reader(or micro Sd card) from a trust supplier (mouser, ...). I don't know if it's possible.

[Olivier]

Next week i will try my screen with 3,3Volts instead of 5 Volts. I hope the built-in SD card will work.

[Xavier]

The best case would be to define 1 reference for the screen and 1 reference for the  SD card reader(or micro Sd card) from a trust supplier (mouser, ...). I don't know if it's possible.

Thanks for the feedback.
I agree, sorry about the problem with the screen dimension... i didn't expect that.
I'll update the BOM with more details.

Using an external SD card reader makes the build more complicated and may not be compatible with future cases (plexi, metal...).

[lokki]

Next week i will try my screen with 3,3Volts instead of 5 Volts. I hope the built-in SD card will work.

So is the screen running at 5v on the preenfm3? I assumed 3.3v but did not yet take measurements...

I think all those sdcard problems come from the fact, that these displays are designed to be run on a 5v Arduino and include resistor dividers as level shifters instead of proper ICs. Probably one could simply solder jumper wires directly from the 4 sdpins to the sdcard slot and it would work. Maybe the three smd resistors would have to be removed.

[Xavier]

Those TFTs accrepts both 5v and 3.3v as power.
The data lines must be 3.3v.

I don't know for the moment what's wrong with some SD card reader, but the 2 that reports problems also have a dimension problems.
What is the value of the 3 resistors you have on the TFT PCB ? I have 1Kohm.
I don't think their goal is to shift levels as the TFT is supposed to have 3.3v TTL level :

http://www.lcdwiki.com/2.8inch_SPI_Module_ILI9341_SKU:MSP2807

[lokki]

The display I bought clearly stated that it is Arduino 5v compatible, the sdlines run directly from the connector via a resistor to the SPI pins, so they have to be for level shifting somehow. (Since Arduino sends out 5v logic).

With 3.3v logic you don't get the right levels I suppose. Unfortunately I can't easily measure, since I have soldered the display to the preenfm3 directly (will make my own smaller case...more later

[Olivier]

The value of the 3 resistors I have on the TFT PCB are 1Kohm.

But the problem seems to be the connection to the SDCard. They are different between my sreen and your screen.

I attach a Jpg file with some numbers on the SDcard Pins.
Pin 1 is connected to R1
Pin 2 is connected to R2
Pin 5 is connected to R3
Pin 7 is connected to MISO

On your Screen
Pin 2 is connected to R1
Pin 3 is connected to R2
Pin 6 is connected to R3

This means that the SDCard connections on my screen are probably wrong.

[Xavier]

I attach a Jpg file with some numbers on the SDcard Pins.
Pin 1 is connected to R1
Pin 2 is connected to R2
Pin 5 is connected to R3
Pin 7 is connected to MISO

This means that the SDCard connections on my screen are probably wrong.

 
Seems like you're right.
That does not correspond to the standard SD pins.. Cannot believe that !!! 
Does R1 go to SD_CS  ?


http://elm-chan.org/docs/mmc/mmc_e.html

[lokki]

This is indeed almost unbelievable...i will check the pictures of my order, but I suspect it is the sameas Oliviers