Schematic Changes & Additions

1. Changed multiple pin connections on SAMD microcontroller

   SAMD pin 13 (PA04): AIN4 → ENAB_RF

   SAMD pin 35 (PA16): NC → PA16

   SAMD pin 37 (PA18): PA18 → VBUS_RESET

   SAMD pin 9 (PB06): RF2_IO1 → RF2_IO0

   SAMD pin 10 (PB07): RF2_BUSY → RF2_IO4

2. Added "one shot" Vbus reset circuit

   Pulling VBUS_RESET high disables the primary regulator (3.3V) for a brief period (~1 second). This allows the user to remotely perform a "clean start" of the board and its various peripherals. VBUS_RESET must be toggled low→high again in order to perform another reset, thereby preventing boot-looping in the event of an electrical short or some other catastrophic failure.

3. Added separate RF regulator w/ enable
   1. Originally U21. Added U7 as a substitute due to global chip shortage.

      ⚠️

      NOTE:

      • If U21 is populated: ENAB_RF must be HIGH to enable RF regulator

      • If U7 is populated: ENAB_RF must be LOW to enable RF regulator

4. Payload connector pinout overhaul
   1. See 🎛Payloads & Interfacing with External Boards for details.

5. Added multiple serial bus isolation circuits
   1. Doesn't impact end user
   2. See 📈Novel Serial Bus Protection for more details.

6. Added an RBF jumper for ground
   1. See 🔓Inhibits & RBF Header for details