I have a board that has a ADC and when powered up by 5.0V I checked the MOSI, MISO, SCLK signals and they are all 3.6-3.7V, is that safe to plug into the Pi system?
On the data output, it's 5.0V therefore I have resistor network to reduce it to 3.3V.
Re: A board with ADC interface with PI.
The CEx, MOSI, and SCLK lines are outputs from the Pi and as long as the ADC accepts 3.3V they will be OK.
The MISO line is an input to the Pi and you should ensure (resistor divider perhaps) that the Pi receives 3.3V.
The MISO line is an input to the Pi and you should ensure (resistor divider perhaps) that the Pi receives 3.3V.