SD reader with other SPI devices

A few days ago I asked a question about how I can connect the Esp8266 with the Arduino UNO via SPI, in the end I had an answer that worked perfectly for me, but another problem arose, and apparently I am not the only one.

Apparently many of the SD readers have a “defect”, and in various forums they suggest adding a triple buffer (I imagine it is an IC, but I have no idea what it is for), as I understand, this makes the SS pin not alter how the SD reader works (I have no idea why they did it that way).

So I need help to know how my Esp8266 (master) can control my Arduino UNO (slave) and SD reader. I think this is a hardware aspect, they say that you have to solder two pins, according to them, it would be to connect pins 8 and 13…

What I do not know is if connecting those two pins would already work as it should, I mean that I would not have to change the code or something like that. But there is another problem : ), I don’t have that version of SD reader, I have this one, which doesn’t have that IC.

Any way to use the SD reader and Arduino UNO to share the same SPI bus?


What's done is to add a gate like 74HC125 to the MISO line, with it's OE/ controlled with the chip select used to access the card. That keeps the SD card from driving MISO when the card is not selected and possibly messing other things up.

The problem that my other devices do not work via SPI is because the SD reader is constantly sending things through the MISO pin?

With that IC I technically make the MISO pin of the SD reader work when SS is in LOW, right?

Yes, it is then only allowed to on the bus when the module is selected.

Wow, that was easier than I thought, it's just a physical aspect and that's it. One more question. Don't you know if there is any transistor that I can use instead of the 74HC125? Because it would be bad spending that chip using 1/4 of its capacity and also I think it spends more energy, since this project is going to be portable.

But thank you very much for your help !!!