Can I Use More Than 8 Chip Select Lines On a SPI Bus With the USB-845X?

Updated May 3, 2018

Reported In

Hardware

  • USB-8452
  • USB-8451

Driver

  • NI-845x

Issue Details

I have more than 8 slave devices I want to use with my USB-845X. Can I use more than 8 chip select lines to communicate with them?

Solution

No, the USB-845X only supports 8 chip select lines. 
 

We have two unsupported alternatives for users wishing to communicate with more than 8 chips using the USB-845x.

  • You can use a multiplexer in order to communicate with a larger number of chips. NI does not sell or recommend any specific multiplexers. 
  • It is possible to can create a custom API to configure the DIO lines to act as chip select lines. However, this is an untested use case, and NI does not have documentation on how to do so. There are minor differences in how the CS and DIO lines behave outside of the script. For example, the SPI Script Disable.vi will tristate the SPI lines in between scripts where the DIO will remain in the last state it was programmed to be in. 

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