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Revision to Using servos and controlling unused IO pins

David Crocker

-Starting with firmware version 1.16, pin numbers in the [[Gcode#Section_M42_Switch_I_O_pin|M42 command]] are logical pin numbers as listed below, not Arduino-like pin numbers. The [[Gcode#Section_M280_Set_servo_position|M280 servo control command]] uses a subset of the same pin numbers.
+== Important note on connecting servos ==
-To see where these pins are on the 2nd Generation Duets, see the [[Duet Wiring Diagrams|Duet wiring diagrams]]
+When a servo stops moving, it can pump a large amount of energy into the +5v rail due to regenerative braking. If unchecked, this may increase the voltage of the +5V rail above the safe limit. The 1.04 revision of the Duet WiFi/Ethernet has an extra 220uF capacitor on the 5v rail to help absorb this, so does the Duet Maestro. Older Duets don't. So when using servos with them it is advisable to add your own 220uF capacitor between the +5V and ground servo wires.
== Logical pin numbers ==
+Starting with firmware version 1.16, pin numbers in the [[Gcode#Section_M42_Switch_I_O_pin|M42 command]] are logical pin numbers as listed below, not Arduino-like pin numbers. The [[Gcode#Section_M280_Set_servo_position|M280 servo control command]] uses a subset of the same pin numbers.
+
''Note that these logical pin numbers are not the physical pin numbers on the expansion header, or the internal pin numbering within the firmware. ''
+
+To see where these pins are on the 2nd Generation Duets, see the [[Duet Wiring Diagrams|Duet wiring diagrams]]
{table

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