I have one of the whizzoo quad MAX31856 boards, and I was wondering how efficiently I can read them..
Would I be able to send the initialization and read commands to all of them by pulling all their CS pins low, transferring the read command to all of them, then set them all high, and sequentially pull them low one at a time and read the value from it?
Manufacturers page of the MAX31856 : MAX31856 Precision Thermocouple to Digital Converter with Linearization | Analog Devices
It is a thermocouple chip.
I can not find a "Whizzoo"-something with four MAX31856. There are different boards (for example on Ebay) with 4 MAX31856 chips. One of them is from "whizoo.com" (with a single 'z'), but I can not find a description of a Quad Channel MAX31856 on that site.
These are the boards : Playing With Fusion - Products: Breakout Boards
But I can not find a Quad Channel board with the MAX31856.
Which Arduino board to you use ?
If you want to combine the SPI bus for multiple devices, the MISO (data input of Master, data output of Slaves) are all shortcut together. Even if you don't use that data, they are still shortcut. Some chips only accept commands with the clock and MOSI, and don't need the MISO signal, in that case they could be combined.
this is the board I have
Edit: I had the wrong listing here (it was for the quad MAX31855 before)
http://www.ebay.com/itm/Quad-MAX31856-thermocouple-breakout-board-for-5V-systems-MAX31855-upgrade/252040638597?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D35389%26meid%3D544eaee743a74796856550ce2594ab22%26pid%3D100005%26rk%3D4%26rkt%3D6%26sd%3D301671408961
Yes, Miso, Mosi, and Clk are all tied together.. the physical part of it is all ok. I'm using a Mega 2560.
What I was wondering was if I can send them all the same command at the same time by pulling all the CS pins low
Thanks
You can, but you will Not get valid readings. Read the datasheet:
Data is output when CS/ is taken low. If you take multiple CS/ low at the same time, then the data on MISO will be corrupted.
I was referring exclusively to writes.. It's completely logical you can't read 2 or more of them at the same time
Read the datasheet - you don't write to the MAX31855. You supply clock and chip select, it starts outputting data to MISO line.
OOps, I notice an error.. Title of the thread is Max31856, which is correct, I misread the ebay listing and ended up with the 31855, and on that one you're completely right, you don't write anything to it.. the Max 31856 DOES have writable registers though...
I would say yes, you can write the same data to the same address of multiple chips in parallel.
https://datasheets.maximintegrated.com/en/ds/MAX31856.pdf
Excellent, that's what I wanted to know 
All the SDO pins are connected. If you do a read, they will be shortcut to each other.
If you do only a write, the SDO stays high impedance (table 5 in the datasheet). I agree with CrossRoads, I would also say yes. However, it is a bad thing to do, because a simple read instruction might damage all 4 chips.