Quote Originally Posted by originalt80 View Post
with this sensor it uses Z axis to compensate for slight changes in the bed.. someone more knowledgeable can explain it better
My understanding is that the firmware will control the adjustment using the Z-Axis. Before actually starting the print a probing sequence is activated to measure the Z-Axis height on each of the three leveling points, if any of these measurements are outside of the specified height (user defined) the printer will stop and display an error message and will not print, however if the height measurement is within the specified height, the firmware will store these new height measurement in memory and compensate accordingly during the print - this means when you set the layer height at 0.20mm and the sensor probing measures the nozzle height at 0.30mm, and 0.30mm is within the specified height, then the firmware will compensate by lowering the Z Axis 0.10mm during printing. NB. once the probing is completed, the sensor is not used or accessed until you start a new print - the firmware will automatically disable auto-levelling on completion of the print.

As for the BLTouch sensor, it has two sets of wiring, a three wire set which needs to be connected to any servo connection points on FFCP board, and a two wire set which needs to be connected to the Z-MIN connection point because this will allow you to use G_CODE like M131 A to probe point 1, M131 B probe point 2, M132 AB activate auto-leveling, M280 P0 S10 push the sensor pin down. So when you send the G_CODE M280 P0 S10, the firmware sends that code to Z-MIN socket, and because the two wire set of the BLTouch is connected to this socket, the internal program of BLTouch will activate the sensor solenoid to push the sensor pin down.

As mentioned in the first post of this thread you must run Sailfish V7.7 release 4.7, when I checked my FFCP I was running V7.7 release 4.2, so I upgraded my firmware.

Hope this helps