Open Access v4 Jumpers

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Hardware Settings and Defaults

AC400 1024x1024 jumpers.png

The Open Access comes ready to run out of the box, advanced users may want to customize their hardware. The following is a list of hardware features that can be selected via jumpers.

Jumper Table

  • 1 USB Power - Enable this jumper to allow the board to be powerd via USB or power an attached accessory.
    • Default: ON
    • Recommend turning this off if you need to ensure that your external device does not remain powered by the OA's 5V USB connection.
  • 2 USB/RPi Selector - Determines whether the Open Access communicates via the mini-USB port or the Raspberry Pi connector
    • Default: Both jumpers UP (USB)
    • Set both jumpers in the pair to "USB" (top) setting to connect the serial output to the FTDI-based USB port.
    • Important: Move both jumpers for proper operation. One jumper is for TX and one is for RX to the Atmgea328P.
  • 3 RS-485 Termination - Enables a termination resistor for end-of-bus on an RS-485 circuit
    • Default: ON
    • Recommendation: Leave this to ON if connecting 0-1 devices, or if it is the last unit in the circuit.
  • 4 Reset Enable - Can be used to disable the resetting and re-flashing of the Open Access CPU
    • Default: ON (Reset enabled)
    • Recommendation: Set this to OFF for increased security; setting it to OFF will prevent a reset and bootloader access. Set to OFF if a USB-attached peripheral may hard-reset and interfere with operation of the unit. Set to ON to allow programming/reset from USB.