Tool/software:
Hello,
I am attempting to use external SPI connections to control the DAC81404EVM. My jumper configuration is as follows:
- IOSEL: none
- level shift enable: disabled
- vdd=usb5v: disabled
- avss=gnd: enabled
I am using an external VIO voltage of 3.3V and external VDD of 5.0V. No AVDD is connected. Any attempt to connect to communicate using the external spi header pins, results in the MOSI line not reaching 3.3V. See the attached picture, where yellow is the clock line, purple is mosi, and blue is sync.
However, if I enable the level shifter, disconnect the external spi (the external power is still connected), and use usb to communicate, the spi voltage levels are good and communication is successful.
I also tried using the old dac81416evm, https://www.ti.com/lit/ug/slau777a/slau777a.pdf, using a similar jumper configuration and the same external voltages. The voltages reached the required levels and communication was successful. I would expect the SPI interfaces between these chips to be very similar; the only difference I can tell between them is that the dac81404evm has a level shifter, while the old dac81416evm does not.
Any insight would be appreciated,
Kevin
