SD SPI MISO sharing issue

Using Arduino Project Guidance
#1

I have been able to get my SD card working just fine with an Arduino Uno. I also have a 165 shift register which works just fine. When I use both at the same time, the SD card is no longer recognizable.

I have tried numerous things, but just cannot get this solved. If I remove the 165 shift register MISO connection, and nothing else, then the SD card works just fine.

Has anyone run into this problem before? Any help would be greatly appreciated.

#2

I buffer MISO coming from SD cards for just that reason. Use 1 gate of a 74HC125, brings it up to 5V level as well. Control OE of the gate with the SD’s chip select pin.
The 74HC165 does not have an OE/, be sure to use a 74HC125 gate there also like a chip select line.

#3

Thanks for that!

Too bad I wasted 3 hours trying everything I could think of and find online to solve it before asking the question. I did learn a few things anyhow…

#4

Looks like the 74HC589 has an active-low Output Enable.

#5

Thanks as well. Good to know.

I've tried it using straight buttons to pins (with a resistor pull up and a cap to debounce). Works fine, but now the memory issues are apparent. I have to remove most of the non MP3 code to get the menus and MP3 to work. The MP3 seems to be a serious memory hog.

#6