Hi,
i want to control two 28BJY-48 (not at the same time) via an ESP32 S2.
If I would use the default control circuit with the ULN2003 I would need 8 GPIOs of my ESP32 S2.
But my ESP is controlling a lot of other stuff and I only have 4 GPIOs left.
Is there any other controller/IC for controlling the 28BJY-48 for example via I2C so it would work with only 4 GPIOs?
Any IC available on DigiKey or Mouser would be fine because it is going to be a custom PCB anyways.
Thanks in advance 
Any STEP/DIR driver will work…
4 pins for two steppers.
All step/dir drivers I know about are for use with bipolar steppers. The 28BJY-48 is a unipolar stepper.
@octarock : You can use a portexpander ( I2C or serial shiftregister ).
Use the TCA9534 with the ULN2003A
Which can, in fact, be operated as bipolar stepper by cutting the red wire's traces on the PCB. A pretty simple mod.
nice so two DRV8825 would work? Couldn't i even get away with two pins in total, as i don't need to change the direction or want to use both at the same time? I could then use one step pin and one en pin for both but the en signal would go into the second driver inverted.
sounds good are there any limitations because I would use a multiplexer?
You have to send 3 bytes the the TCA9534 to set the bits on the output port. That would be around 30 bits at 400kHz. So it would take about 75usec to do one step.
So the maximum step rate would be around 13333 steps/second. Probably closer to 10,000 when you add in the software overhead when you do a digitalWrite()
Should be fast enough for you application
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