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systems intended for the A4988 that route logic power to the FAULT pin will effectively
have a 10k pull-up on the SLEEP pin. (This 10k resistor is not present on the initial
(md20a) version of the DRV8825 carrier.)
The current limit potentiometer is in a different location.
The relationship between the current limit setting and the reference pin voltage is
different.
The DRV8825 offers 1/32-step microstepping; the A4988 only goes down to 1/16-step.
The mode selection pin inputs corresponding to 1/16-step on the A4988 result in 1/32-
step microstepping on the DRV8825. For all other microstepping resolutions, the step
selection table is the same for both the DRV8825 and the A4988.
The timing requirements for minimum pulse durations on the STEP pin are different for
the two drivers. With the DRV8825, the high and low STEP pulses must each be at least
1.9 us; they can be as short as 1 us when using the A4988.
The DRV8825 has a higher maximum supply voltage than the A4988 (45 V vs 35 V),
which means the DRV8825 can be used more safely at higher voltages and is less
susceptible to damage from LC voltage spikes.
The DRV8825 can deliver more current than the A4988 without any additional cooling
(based on our full-step tests: 1.5 A per coil for the DRV8825 vs 1.2 A per coil for
the
A4988 Black Edition
and 1 A per coil for the original A4988 carrier).
The DRV8825 uses a different naming convention for the stepper motor outputs, but
they are functionally the same as the corresponding pins on the A4988 carrier, so the
same connections to both drivers result in the same stepper motor behavior. On both
boards, the first part of the label identifies the coil (so you have coils “A” and “B” on
the DRV8825 and coils “1” and “2” on the A4988).
For those with color-sensitive applications, note that the DRV8825 carrier is purple.
In summary, the DRV8825 carrier is similar enough to our A4988 carriers that the
minimum connection diagram for the A4988 is a valid alternate way to connect the
DRV8825 to a microcontroller as well:
