Hey Nicholas, hey Jeff,
a switch from EStop (Pin 23) to Ground (Pin 25) (=Logic low).
If you connect a “Normally Open” Switch (NO), in the “I/O Configuration” Tab, “estop” must then be set to “normally open”. If you connect a “Normally Closed” Switch (NC) you must set it to “normally closed”.
Pin 20 should measure 3.3 V against ground.
3.5.25-pin I/O Port - Buildbotics Controller Manual
POSSIBLE
PIN NAME I/O VALUES DESCRIPTION
---+-------+---+-----------+-----------------------
23 | EStop | I | Open, VIL | Emergency stop switch
---+-------+---+-----------+-----------------------
LOGIC
NAME MINIMUM MAXIMUM DEFINITION
------+-------+---------+----------------------
VOL 0 0.76 VDC Logic output low
VOH 2.6 VDC 3.3 VDC Logic output high
VIL 0 0.6 VDC Logic input low
VIH 2 VDC 3.3 VDC Login input high
V3.3 3.3 VDC Voltage found on V3.3
Output when unloaded
Note: The National Fire Protection Agency (NFPA 79) requires that the class of emergency stop button be determined through a risk assessment. The soft “emergency stop” button on these web pages and the estop pin (pin 23 on the DB25 I/O connector) are both software controlled, and cannot be used for safety. If your risk assessment requires an emergency stop button to be installed for safety purposes or mission critical applications, then Buildbotics LLC recommends installing a “listed“ hardware Emergency Stop button in line with system power.