In my application I have two SPI devices on the same bus. After some testing I found a “bare” µSD Card Adapter (basically a socket) does not Tri-State the MISO pin. The other device on the SPI bus did not like thissituation.
Does the above referenced breakout board Tri-State the MISO pin when CS is high? I looked at the TXB0104 spec and could determine the usage as they are bi-directional.
Thanks
John
Hi John,
I think you will need to either use an external tri-state buffer to use this breakout with multiple SPI devices or modify the MicroSD Card Breakout, as I do not believe this breakout Tri-States the MISO pin when CS is HIGH. Per the [datasheet, the TXB0104 does have an output-enable pin that, when driven LOW, will put all outputs into a high-impedance state so you could potentially modify the breakout to control that pin. The board ships with that pin connected directly to Vcca (3.3V) so you would need to modify the board to disable that trace and attach the pin to something to pull it LOW when you want to start/stop transmission from the SD card. I am not sure if that will cause weird behavior from the SD card, though. It shouldn’t since all it is doing is disabling the output but it’s not something we have tested.](https://cdn.sparkfun.com/datasheets/BreakoutBoards/txb0104.pdf)