Help with Switch Problems

Help with Switch Problems

Checking Switch Status.

The active/inactive status of all switches can be checked with the "?" command. Use a serial port monitor to send the command. The status will look something like this...

<Run|MPos:351.154,0.000,-135.983,10.477|FS:1200,0|Pn:X>

The Pn:X part will only show if at least one switch is active. In this case, the X limit switch is currently being read in the active state. Every switch can be checked. These are the possible switches you could see PXYZABCDRHS

• P = Probe
• XYZABC = The axis limit switches
• D = Door
• R = Reset
• H = Hold
• S = Start

Check all your switches in in the active and inactive states and make sure the status query response show the correct status in both states.

Inverted States

If your switches are reporting inverted from what you expect, this can be corrected in firmware. You can invert all limit switch pins with the **$5*8 setting. You can invert the probe pin with the $6 setting.

You can invert the control pins (DRHS) by flipping the appropriate bits #define INVERT_CONTROL_PIN_MASK B1111 mask in config.h

You can invert individual limit switch pins with #define INVERT_LIMIT_PIN_MASK ((1<<X_LIMIT_BIT)|(1<<Y_LIMIT_BIT)) in config.h

Switch Pull Ups

Note: a few I/O pins (34 through 39) require external pull ups (or down) resistors. If you do not have resistors on these pins, the I/O pin will "float" and not have a deterministic" state. Most ESP32 controller PCBs, that use these pins have a pull up installed already.

Homing FAQ

• Why does the axis move a little them give an ALARM 8? This is normal behavior if switch is active before the homing starts. Grbl tries to clear the switch by moving away by the $Homing/Pulloff amount. Check the switch before homing. Is it touched? Does the status show it as touched? What is the status if you touch it?