Review on KeeYees Micro Adater Reader Module by Barry Shaker

This SD adapter will work fine as long as it is the only device on the SPI bus. It's the wrong design. Although it has a 74LVC125 four position switch with 4 output enable pins, all 4 output enable pins are permanently grounded (on). This means that the MISO output directed to the uController WILL ALWAYS BE CONTROLLED! While the CS pin goes through the level switch to the SD card, the CS pin must also be connected to the MISO output enable pin on the level switch itself so that when CS is high, the MISO pin tristates as required by the SPI protocol . The end result is that you have an SD adapter that always drives the MISO pin even when CS is high, overloading the SPI bus and preventing other devices from using the SPI bus. .The design can be corrected by the following refinement: 1) raise pin 13 of the level switch from the platform, 2) connect pin 13 of the raised level switch to the left side of R1 with a jumper, 3) add a pull-up resistor between the right one side of R1 and VCC, for example on the right pin voltage regulator. The revision causes the 4OE pin on the level switch (output enable for the MISO pin) to be driven by CS instead of GND (on the pad), the CS pin must also be pulled to VCC when the microcontroller is tristating CS. for example during reset and before SD driver initialization.