Ok, so I can get this to work if I run the PWR, GRND and DINOUT (Yellow) from the thermocouple amp and into pins 5V/3.3V, G and G5 using jumper wires instead of physical GROVE port on m5stack.
I then changed my code so the OneWire bus was using pin GPIO pin 5. Everything worked as expected. All good.
However, I am looking for something a bit more robust for prototyping then jumper wires i.e physical GROVE connectors with a hub for multiple. I noticed on the product site that alot of the units have a GROVE connector however they are NOT i2C i.e potentiometer unit so I figured I could do the same with this type of connection which is not I2C but one wire. I guess my assumption was wrong. I do see in the doco refrences to GROVE A and GROVE B? What is the difference from a connection point of view and from a programming point of view?
However now that I have got it working I can only assume the physical GROVE port on the M5stack is just for I2C devices. Am I correct? Is I2C enabled by default or should I be turning it off for non I2C stuff?
I also have a GROVE I2C mosfet that I need to incorporate into my build which I'm pretty sure will work with the GROVE port. But I really wanted to be able to have a hub where I just added the various sensors etc without jumper wires