Help me with the MCP3911 analog front end diagnostics

HI friends,

I am trying out the MCP3911 (SSOP-20 version) as a analog front end for my Teensy 3 in power measurements and the code i am using is based on the Arduino IDE. So far, I am struggling with getting the chip to even acknowledge SPI communications, so I wanted to ask a couple of questions to help me with the diagnostics... Thank you in advance for any help!

1) Is the SPI interface de-coupled from the main system clock? The reason I ask is that I am using the maximum allowable clock crystal speed (16MHz) and wonder if that could be leading to an issue, even if the teensy can run SPI fine at 16MHz (clockdiv4 @ 48MHz CPU frequency).

2) The MCP3911 MCLK crystal has a 18pF load capacitance requirement and I am using a pair of 33pF capacitors, does that seem reasonable? (i.e. 2CL-3pF)

I would attach you the datasheet of MCP3911 http://www.kynix.com/uploadfiles/pdf2286/MCP3911A0-E2fML_70919.pdf

Hi, Welcome to the forum.

Please read the first post in any forum entitled how to use this forum. http://forum.arduino.cc/index.php/topic,148850.0.html then look down to item #7 about how to post your code. It will be formatted in a scrolling window that makes it easier to read.

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom.. :)

Apologies, I just noticed I have forgotten to reply to you with the issue, Tom.

I've stuck to the suggested values and my initial set of power measuring results are within 0.003% of a yokogawa WT210, which seems pretty good. I'll have to dig a bit deeper to test higher power conditions, non PF=1, temperature swings and so on. But for residential indoor use, these results are promising.

Thanks for trying to help my friend, Best wishes!