How is M307 R Parameter Calculated?

[ctilley79]

Since I have my hotend heater on the 3HC expansion board, and remote heater tuning is not supported because god knows why, how do you manually calculate the R parameter since the A parameter is now deprecated? is there a process or a conversion?

While we're on this topic. What prevented proper implementation of heater tuning on the expansion boards?

[dc42]

The R parameter is the rate at which the heater temperature would rise if it were perfectly insulated. The relationship is approximately A = R * C.

Heater tuning on expansion boards is working in firmware 3.3beta, which is already available on Dropbox. https://forum.duet3d.com/topic/20991/early-rrf-3-3beta-files-available?_=1613029395307