Stepper Motors (Part 5)

Part 12, 3, 4, 5, 6, 7, 8, 9

The A4988 in details

pololu_3

Previous posts described the basic use of the A4988 driver. We shall get deeper in the A4988 driver in order to achieve the ultimate driving performances.

Apart from the STEP and DIR pins the A4988 driver features additional functions addressable through the following pins

  • ~RESET: the ground true RESET input sets the translator to a predefined “home state”, and turns off all of the FET outputs. All STEP inputs are ignored until reset input is set to HIGH. The RESET input is floating and should be connected to GND or VDD at any time. It is a valid option to connect the RESET input to the neighbour SLEEP input which is pulled at a HIGH level by internal resistor.
  • ~ENABLE: When the ground true ENABLE Input is set to a logic HIGH, the outputs are disabled. When set to a logic LOW , the internal control enables the outputs as required. The translator inputs STEP, DIR, and MSx, as well as the internal sequencing logic, all remain active, independent of the enable input state.
  • ~SLEEP: A logic LOW on the ground true SLEEP input turns the translator in sleep mode in order to minimize pits power consumption. A logic HIGH allows normal operation, as well as start-up. Wake up lasts at least 1ms.
  • MS1, MS2 and MS3:  The microstep resolution is set by setting the inputs MSx according to the following table.  The MS1 and MS3 pins have a 100 kΩ pull-down resistance, and the MS2 pin has a 50 kΩ pull-down resistance. When changing the step mode the change does not take effect until the next STEP rising edge.
MS1
MS2
MS3
Microstep Resolution
L
L
L
Full Step 
H
L
L
Half Step
L
H
L
Quarter Step
H
H
L
Eighth Step
H
H
H
Sixteenth Step

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