ABStick

This is a StepStick module that instead of using the four output pins to operate a stepper motor it presents Gnd, +5V, A, B (A/B inputs) for reading a quadrature (or CW/CCW) encoder.

The pins typically used for Step and Direction (or Step and MISO-RX) instead travel to the microcontroller as inputs from the encoder.  Since most microcontrollers are not 5V tolerant this module has a level shifter to drop the A/B signal levels to 3.3V (supplied by VCC from the StepStick Socket.)

Finally since most StepStick sockets do not have 5V present this module has a linear regulator to convert Vmot (in the range of 5.8 to 12VDC) to 5V to power the encoder.

Revision History:

0.9 - First release

0.91 - Added ENable pin control and a 10K pull-down resistor so the AB outputs are floating at boot by default.  Note that some board designs have one shared enable signal to all stepper drivers and/or pull the enable signal logic HIGH at boot.  Often the enable state at boot doesn't matter, but for the MaxESP series Axis3 Step (GPIO2) can't be driven logic HIGH at boot so the enable signal must be logic LOW to be sure that doesn't happen.  At any rate the Enable signal must be driven logic HIGH once OnStepX boots (just as the DcStick requires.)