I bought thisMAX31855K K-Type Thermocouple Sensor Breakout 4ch and I'm able to read one thermocouple fine, but what I really want to know is, how can I read all 4 thermocouples?
since the boards has only 1 SCK, 1SDO?
Thanks
Steve
Note the four "chip select" lines CS0-CS3. Pull one and only one low at a time to read the corresponding chip, leave the others high. All the chips are connected together on an SPI bus, the chip select signals do just that -- select the chip you want to talk to. You could connect four pins from the MCU to the CS lines.
But if I want to be able to read( Monitor) 4 chip set at the same time. can I still do this with 1 low and the rest high?
Strictly speaking, more than one chip cannot be accessed at the "same" time. They are all on the same bus and if more than one tries to talk simultaneously, it would be a mess, the data would get corrupted.
However, the four chips can be read sequentially, one after another, and this is very fast. It would work something like this:
- start with all four CS lines high.
- make CS0 low, read chip 0, make CS0 high.
- make CS1 low, read chip 1, make CS1 high.
- etc.
All four could be read in probably a millisecond or less, is that close enough to the "same" time? Not sure how frequently you need to read the chips, but they require 100ms to do the A/D conversion, so there's no point in reading them more often than that.
PS: See Serial Peripheral Interface - Wikipedia for a description of the SPI bus and how it works with multiple devices. Your board is basically connected like this, although of course there are four slave devices on the bus. The Slave Select (SS) lines are the same as Chip Select, just a different name for the same thing.