We have a SPI device that is 2.5V only connected to the Integra. We have placed a bi-directional level translator, a TXB0104, in-between the Integra and the SPI device. When the 2.5V device transmits data on the data line (SPI_D[0] in this case), we see the following waveform:
You can see the sharp uptick on the leading edge of the pulse as the one-shot in the TXB0104 fires. But then the voltage returns to about 2.5V which is below where I need for it to be for the Integra to see it as a 3.3V high. The output impedance of the TXB0104 is 4k ohms after the one-shot has fired and this picture is consistent with about a 10-13k pull down on the line. We have measured the resistance of the line with the power off and it is >200k to ground so we believe that there is a pull down on this pin (N11).
The data sheet says this is the case so I program the PINCTRL171 line (0x4814 0AA8) to be a 0x08 which should turn off the pull-down, but the behavior persists. In fact I also changed it to a pull up (0x10) and it does not seem to change. Is there any reason to believe that this PINCTRL does not work?
Steve
