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Questions relating to designing PCBs
By Daemach
#151208
I'm trying to use a TXS0108 to translate 3.3v to 5v I2C and SPI. The I2C side works great, but the SPI side doesn't. It seems that MISO and SCK are being driven high, possibly due to the pullup resistors in the TXS0108. This interferes with all of the SPI devices as well as trying to burn a bootloader.

The TXB0108 doesn't use pullups.

Should this be working? If so, what am I missing? I'm using an atmega328 and arduino code to drive this. If I should be using the TXB line rather than the TXS line, do I need to add pullup resistors on both sides of the i2c lines? The devices plugged into the i2c bus should all have their own pullups. Does the atmega328 pull up the SDA and SCL lines? What is safest/most robust?

TXS - http://www.ti.com/lit/ds/symlink/txs0108e.pdf
TXB - http://www.ti.com/lit/ds/symlink/txb0108.pdf

Any help would be appreciated!
TXS0108SPI.png
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