@drew-p From the IMU mfg. website:

@marciocobra Since no one has responded...
to what does it not connect?
Do you have the USB programmer, I presume?
Does it not connect to Arduino IDE port?
Or ESP_NOW, or WiFi or Internet!

My advice works on any IMU on any microcontroller.
You can figure it out yourself, it's fun and part of the challenge.!
Lying flat on the bench, "UP" (towards the camera) is Z axis. Rotate to side and on end to determine other axes.

@drew-p Simple answer to any IMU:
Just put it flat on a surface. The axis that shows ~ 1.00 is 1 gravity, the others should be ~ 0.00

Shown here is the AtomS3 built-in IMU with the third reading (az) showing "1g" .
You can roll it on its side to see x or y.
Hope this helps.
-Terry

@mchott Speaking personally, I would have the Master also arbitrate the Slaves by polling them one at a time. Yes, they can all talk at once but it's messy. I have a Master talking to two Slaves ESP-NOW peer to peer with small size of data and no urgency in the process. I may send a simple boolean flag to one to turn on a heater, next sending a int value to the other to set a servo position. (this one also returns a float with the Vent Temp.

@rh1972 said in "#include <M5Core2.h>" doesn't compile:

c++allocator.h

My recent install of Arduino V2.0.3 doesn't have c++allocator.h installed and I could not find it anywhere in my computer.

So, yes! I agree there must be something else wrong.
Are you using Arduino V2.0.3?

Hi!
I verify this simple code no problem.
#include <M5Core2.h>
void setup() {
}
void loop() {
}
Is this what you were talking about?
-Terry

@ajb2k3 I really like the idea of REPL !

MY(!) aging brain is resisting learning a new programming language.

In the (late) 70's I programmed in machine code and felt C was a "high level language".

I will investigate Python, could be fun!

Cheers to all.