+ User Manual
I/O enable
To prevent I/O conflicts and glitches on (stepper or power) outputs during initialization, the
inputs and outputs are isolated from the BeagleBone during start-up. Once the BeagleBone
has booted it is the responsibility of the user (application) to initialize the outputs to safe
values before enabling the I/O. Enabling the I/O is done by by setting an gpio signal
appropriately: gpio66 must be configured as output and set to a logic '0'. This activates a
circuit that enables the level shifters for the inputs and buffers for the outputs.
On the +, the I/O enable signal is also to the Emergency Stop circuit. ESTOP must be
negated before I/O enable can be activated via gpio66. The + has a red LED (D23,
marked IOE) that turns on if the I/O enable signal is active.
Another override is via pin #2 on J5. If this pin is pulled low, all stepper driver outputs are
disabled (tri-stated). This feature can be used to prevent overloading the stepper outputs
when external stepper drivers with a separate power source are being used. Depending on the
type of inputs used, these inputs may form a short circuit for the stepper drivers while the
supply is turned off. In that case connect the driver's logic supply to pin #2 on J5 to disable
the BeBoPr outputs while the drivers are turned off.
version 1.4.9 (09/04/14)
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