So I've finally competed my Hottop mod to be able to drive the thing over USB from my laptop. I know others have done this with various different methods, I started off using a TC4 (google it if you're not familiar) and building my own interface board but the group that sell the TC4 boards started offering a hottop interface board half way though my project which also allowed safety features to keep running (better than my interface board anyway). It's a pretty cool offering because you can pretty much "plug and play" for USB control of your hottop with the addition of the HTC interface.
Given the TC4/HTC setup there are a few different ways to implement this, I didn't have the best success with the internally mounted thermocouples and wasn't able to successfully insulate the thermocouple to my satisfaction. I'm sure there will be those that think the thermocouple mount holes in the back of my hottop are not how they would do it but thats the beauty of it, you can implement it however you like.
I've completed the first few roasts and I am seeing a consistency between the legacy heat/fan control and the TC4 control, have a look at the picture of the profile I've attached. Note it may look a little like CS RoastMonitor but actually it's a custom application I've been developing for this project. I had issues with Artisan on lower power machines and at the time I started the project I don't think RoastLogger supported Arduino/TC4. Also note that the profile is quite atypical, I am experimenting with very fasts roasts on Ethiopian Ghimbi which works because it is very low acidity, its working out well so far So the coloured stuff is the TC4 driven roast and the green in the background is the previous hottop controlled roast. I did use an amp meter to compare the TC4 control vs the hottop control and see the fan/heat power draw is pretty close.