Hello,

I'm using I2C MCP23017 to control a stepper motor driver. The driver board needs TTL high/low for forward and TTL low/high for reverse. I'm looking for a circuit, maybe a flip flop, so that I only have to use one high/low line from the MCP23017 to cause the driver board lines to flip from high/low to low/high. Anyone know of a circuit or chip that will do what I'm looking for? In case you're interested, I'm using the TA7291S/SG driver chip.

The logic would look like this:

H = H/L
L = L/H

TIA

Here is a copy of my current circuit, A, which works fine. And circuit B that would only use one line from the MCP23017. I'm just not sure what to place between the MCP23017 and the TA7291S to make it happen.

Maybe a NOT gate tied to one? A 74LS04?

 

The typical stepper driver requires either a low or high for each direction and the step series of pulses to control rate or speed.
Max.