SPI slaves and master hardware connection

nia · Joined: 23 Dec 2010 Posts: 8

Hi,

How to connect a PIC (Master) to 70 PIC (Slaves) in SPI? I wonder, a direct connection of SDO, SDI, SS and SCLK between a master and multi-slaves will work? especially the SCLK, do we need buffer? pull up?

My master is dsPIC30F6014A, and the 70 slaves will be dsPIC30F4012

TQ,
Nia

temtronic · Posted: Thu Dec 30, 2010 3:23 pm

You'll have to read the data sheets to compute the fan-in, fan-out of those devices and depending on the physical distance between them vs. speed to see if buffer devices are needed.

Easy enough to read the info, R&D say 5 devices, then 10, then 20,etc....to see what happens in the real world.

My systems handle 128 remotes over 18 miles of copper using a single wire interface, so your 70 devices are possible but you'll have to start small and build on what you learn.

Noise and grounds are two issues to look into!!