Hello,

I'm very new to circuit design in general so I apologize if my question is obvious.
I want to connect the www analog com/media/en/technical-documentation/data-sheets/ADIS16209.pdf
to the WhisperNode LoRa.
I've read various seemingly conflicting information online regarding which lines require/benefit from pullup/pulldown resistors and which connections I would need to make to operate the unit at very low sleep power.

From a general perspective it seems like for SPI you can directly connect most of the connections to the MCU.
However looking at your schematic it seems you put pull-up resistors on the CS and pull down resistors on the RST.
bitbucket org/talk2/whisper-node-avr/raw/2431a88997413b6a430d4d918621e661a171b600 Documentation/Whisper_Node-AVR_0.3.pdf
Is this purely to make it so that if one of the SS or RST MCU pin is not initialized the behavior of the RFM69 will be defined? Or does this have some benefit for the sleep power usage? If it does have an effect on sleep power would the same configuration be sensible for the ADIS16209? Would similar resistor values make sense? And would my circuit benefit from the capacitors on VDD/VCC like you have?

From what I understand from the following page.
github com/juchong/ADIS16209-Arduino-Demo
Only the following 8 PINS need to be connected to the MCU.
SCLK, DOUT, DIN, CS, GND, VREF, VDD, RST

Can you make any recommendations about which PINS on the WhisperNode would be best connected to each to avoid conflicts. From the documentation at bitbucket.org/talk2/whisper-node-avr-lora
A1, A2 and A3 appear to be the only PINS that are not currently used that I could assign to CS and RST for the ADIS16209 (without disconnecting a jumper for one of the LED's for example).
Is there any benefit to use the D## pins vs the A## pins (for power or otherwise) (If so which D## pins would you recommend re-purposing)

My current thought is as follows.
MCU ADIS16209
D11 (MOSI) -> DIN
D12 (MISO) -> DOUT
D13 (SCK) -> SCLK
A01 -> CS (not too sure if A01 is the best choice or not. also not sure if a pullup would be a good idea)
GND -> GND (does it make any difference which pin I take it from?)
3V3_R1 -> VDD (does it make any difference which pin I take it from? also not sure if caps would be beneficial)
A00 -> RST (not too sure if A00 is the best choice or not. also not sure if a pulldown resistor is a good idea)

I apologize for asking so many questions at the same time. Any input you can provide would be appreciated as I'm designing a breakout board to have made so I can connect the ADIS16209 to my WhisperNode and want to make sure I do it right the first time.

UPDATE:
I removed my references to VREF as I realized it's an output, I also scrapped the idea of a stackable header as I want to potentially change the pins used on the whispernode. I've also attached a schematic.
Also I wanted to know if floating pins are bad from either a power perspective or a noise perspective?

Thanks!

https://s26.postimg.org/4n5aam7vb/adis1 ... eakout.png

Hi Peter,

I believe your assumptions are correct, I would just suggest a small change:

D11 (MOSI) -> DIN
D12 (MISO) -> DOUT
D13 (SCK) -> SCLK
A01 -> CS (A01 is OK, you do need a pull-up, like 10K or 100K)
GND -> GND (Any pin should work)
VREF -> VREF - Not sure about this one.
3V3_R1 -> VDD (Doesn't matter which pin. You normally need a decoupling capacitor, like 0.1uF as close as possible to the IC)
A02 -> RST (A00 is being already used, pick the A02. You need to check if a pull-up is required or not. Again if necessary a 10K or 100K should work).

Any additional circuit maybe listed on the ADIS16209 datasheet, maybe an example design. I know the quantity of information on the datasheets can be overwhelming. Always read and take nodes so it helps remembering the details.

Additionally, searching other designs using the same ADIS16209 on the Internet might help you.

Thanks a bunch!
Thanks for also mentioning VREF, I figured out it was an output not an input .
Also thanks for encouraging me to review the datasheet again. In one of the footnotes it says there is an internal pull-up on RST because it is active low.
I guess I needn't worry about the remainder of the floating PINS.