Please note, that the limit switches should be operational at this point, before going further!
Also, now is an excellent moment to re-check the tube movement: I recommend that for setup, you loosen the springs and use the weight of the tube as a starting point. When you push the tube up, it should go up, triggering the switch. Then, the bottom collar should go against the lower tubing. Only after this, would the spring in the nozzle adapter start to compress. When you let go, the tube should drop fully down under its own weight, at all rotational positions. If this is not the case, fix it, as the next steps will mask the error, which is later hard to diagnose.
If you haven’t done so yet, attach a nozzle to the pickup tube. If you triggered the switch at this or the previous chapter, press reset on the TinyG and after the message, click “Clear error” to re-establish connection.
On the Basic Setup tab, Nozzle height box, put 0.5 to Switch hysteresis box. Then, click calibrate, and follow the instructions. First, you should place a regular height PCB under the nozzle; you can jog the machine to a suitable position for this. Clicking next will take the nozzle down until the switch triggers, This is the full Z0 to PCB surface measurement.
Then, you are asked to jog the nozzle up until it just touches the PCB. Pressing F11 will take the nozzle up 0.1mm at a time, Shift+F11 is 1mm up. Do not try to move the machine in XY direction during this! It is sufficient accuracy to take the nozzle up until you see that it is not touching anymore, then one F12 press, 0.1mm down. This establishes the nozzle backoff value. If the backoff value turns out to be significantly less than 1mm or so (2mm recommended), adjust the Z Max switch (the limit switch resting against the gear) and do this again.
The placement depth is the value down from backoff height, that is used for placement operations. For now, set it half of backoff. Note, that this value controls both the pickup/placement force as well as guards against false triggers.