Do I need to use DRDY? (MAX31865 to ATMEGA328 TQFP running Uno bootloader)

Using Arduino Networking, Protocols, and Devices
1

Hi folks,

I'm learning to use SPI communication to read from two separate MAX31865 RTD temperature sensor chips. They have a DRDY (data ready) output pin on the MAX31865. Do I need to read that pin on the ATMEGA or can I just leave it not connected like so many other SPI devices. Here's my setup from the ATMEGA:

Chip Select Pins:
ADC6: SS1 to IC1-CS
ADC7: SS2 to IC2-CS

Standard Uno ICPS/SPI port:
D11: MOSI to IC-SDI
D12: MISO to IC-SDO
D13: CLK to IC-SCLK

What to do with these from the IC's? Do I even need them?
DRDY1?
DRDY2?

Thanks for your insight.
datasheet: http://datasheets.maximintegrated.com/en/ds/MAX31865.pdf

2

You can not use them. Allow enough time for the conversion to complete. (50mS, something like that, its in the datasheet).

This will be a problem:
Chip Select Pins:
ADC6: SS1 to IC1-CS
ADC7: SS2 to IC2-CS

ADC6 & ADC7 are analog input ONLY pins on TQFP package parts. They have no digital input/output capability.

3

Thank you for pointing out the wrong CS pins. I suppose I can easily switch those in my design. Do the other analog pins (0-5) still double as digital pins, like the PDIP package?

Any advice on the DRDY related question?

4

I answered the drdy questionn already.

5

Sorry, it just wasn't clear to me by the wording "them." I thought you were only talking about the analog pin problem. So, to make sure I have your answer clearly, I'm assuming you mean not to use the DRDY output of the MAX chip and just wait for it's data output upon sending the CS signal (depending on SPI mode?). Correct me if I'm wrong... thanks again.

6

Yes, just wait for the conversion to complete. I was using 60Hz, single conversion, so 55mS wait time.

Sorry about the confusion over the ADCs.

7

Got it. I've used SPI stuff before but never encountered DRDY and wasn't sure if it was required for this chip's operation. I'll leave it disconnected.