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

Hi, Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.,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!