LTC6804 SPI connection to RPi3

Hello

I'm trying to make SPI connection between LTC6804-1 and Raspberry Pi3 Model B; I'm new to SPI and I encountered with a couple of questions:

1- If I want to make SPI connection through MATLAB, then the speeds that I can set for SPI, start from 500kHz. Is this ok for continuous reading of voltage measurements?
2- In addition to 4 wire connections (SCLK, MISO, MOSI, CS) should I connect grounds of two boards together?
3- I need to use 3.3 volt signals on my RPi3 and because SPI voltages on LTC6804-1 are 5 volts, then I'm going to use resistive divider; is there any special point that I must take into consideration?

Thanks,
Mahmoud

  • 0
    •  Analog Employees 
    on May 12, 2017 9:21 PM

    1- If I want to make SPI connection through MATLAB, then the speeds that I can set for SPI, start from 500kHz. Is this ok for continuous reading of voltage measurements?

    Yes any SPI clock frequency up to 1MHz will work with the LTC6804


    2- In addition to 4 wire connections (SCLK, MISO, MOSI, CS) should I connect grounds of two boards together?

    Yes the grounds of the boards should be connected together when using SPI.


    3- I need to use 3.3 volt signals on my RPi3 and because SPI voltages on LTC6804-1 are 5 volts, then I'm going to use resistive divider; is there any special point that I must take into consideration?

    The LTC6804 will work with  3.3V logic, you can drive the /CS, SCK and SDI pins directly from the raspberry pi. The SDO of the 6804 is open drain so you can simply tie the pull up resistor to a 3.3V rail when interfacing with the raspberry pi. If you are using the LTC6804 demo board the pull up resistor(R63) is not installed. So you will need to add a pull up resistor on the MISO (SDO) line anyway. I would recommend using a 2-5k resistor.