@gloomyandy said in How to use M915 T parameter:
@NeoDue What makes you think the default value is 0? 0 is and was the default value for COOLCONF, but the "default" value (i.e. the value that RRF will set when it boots) for TCOOLTHRS. The value set by RRF is equivalent to setting a M915 H value of 200 (which ends up being the hex value 0xea).
You are right, I had your post https://forum.duet3d.com/post/332054 in mind, but that one is about COOLCONF.
As I mentioned above I'm not sure that it is a good idea adjusting these values unless you understand exactly what the consequences are. This is particularly true given that you are seeing layer shifts. I think you did test for layer shifts with the M915 settings removed, but if not it would probably be a good idea to do so.
Yes, I fully understand that, and as I had noted in the layer shift thread, I did testing without these as you had asked me in this post. (Apart from that, this value does only affect StealthChop behaviour, therefore it should be ignored as soon as I switch to Spreadcycle)
Technically, I see this setting as follows...
The datasheet says:
TCOOLTHRS ≥ TSTEP ≥ THIGH:
- CoolStep is enabled, if configured
- StealthChop voltage PWM mode is disabled
TCOOLTHRS ≥ TSTEP
- Stall output signal (DIAG0/1) is enabled, if configured
CoolStep and Stall output is not configured on my printer, therefore these two settings are not of interest.
But since thigh is set to 5 on my printer to ensure TSTEP ≤ THIGH does not happen (again, I had disabled this for the input shaping test when you asked me to), I need to set tcoolthrs to a value below 5 to ensure the case "StealthChop voltage PWM mode is disabled" never happens. This seems to be the same behaviour as the TMC2209 of the original controller board works (edit for clarification: but there, without having to set tcoolthrs) - tcoolthrs works different there if I trust the datasheet.