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Synchronize two USB 8452 with the same clock

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I want to communicate to 16 sensors via SPI or I2C. However, due to the limitation of number of digital lines ( 8 in total) the USB 8452 has, I was wondering, if its possible, to connect two USB 8452 on a same computer and sync the two of them with the same clock.

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Accepted by topic author shazamraptor

Let's talk about these protocols.

 

In SPI, all of the devices share the same CLK, MOSI, and MISO lines, and the slaves are addressed by a chip select (CS) line. There are 8 of those chip select lines on the device, so you can only have 8 SPI devices connected to these, and in SPI there can only be one master, so that's the limit with this specific hardware.

 

In I2C, all of the devices share SCL (clock) and SDA (data), and are all connected to the same wires and addressed by an actual address transmitted across the data line. There are limits to the number of slaves you can have, but generally, all of those limits are well above 16. You should be able to communicate with 16 I2C slaves from one USB-8452.

 

Bonus: Here's an image (not NI's) of an I2C bus and its topology

 

Edit: I guess I also forgot to mention this. You don't actually use those general digital I/O pins for anything involving these protocols. Those are just extra pins you can use if you need extra digital I/O

C. Weeks
Product Support Engineer
NI
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Thanks for your reply. We were trying to connect via SPI using a PCI6221, but recently ordered a USB8452. We are going to tackle it then by using I2C. Thank you for your response.

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