Oops - output voltage swing not big enough
1484 Views - Created 30/05/2018
You could use an op-amp to amplify the output voltage.
The second option, if you don't mind having the ADC DAC Pi separate from the Raspberry Pi is to use a buffer on the SPI bus and run the ADC DAC Pi at 5V. On the Expander Pi, we use a 74HC4050 buffer powered by the 3.3V supply on the Raspberry Pi. The inputs on the 74HC4050 are tolerant of voltages up to 15V so you can power the ADC DAC Pi from the 5V rail on the Pi and the 74HC4050 will act as a level shifter for the SPI bus. The Expander Pi schematic shows which pins need to be connected on the 74HC4050 to the SPI pins.
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