dfrobot Gravity: Digital Peristaltic Pump

AI context

Dense context for pasting into a model prompt — addresses, pinout, voltages, tolerances and the vendor's reference circuit.

PART: DFRobot Gravity: Digital Peristaltic Pump, SKU DFR0523 - a 27.4 x 28.7 mm driver board plus a 6 V DC-motor peristaltic pump head with BPT tube (3 mm inner diameter, 5 mm outer). The vendor names no part number for the driver or the motor anywhere on the page or the wiki, so part is null and there is no data sheet to link.
ADDRESSES: none. There is no bus on this board - it is driven by a single servo-style pulse train.
PINOUT: five pads, numbered as the vendor's own pinout table numbers them: 1 D, the control-signal input that takes the PPM signal; 2 +, power VCC 5-6 V; 3 -, power GND; 4 M-, the motor's negative terminal; 5 M, the motor's positive terminal. Pads 1-3 are the Gravity PH2.0-3P connector; pads 4 and 5 are the pump motor's two wires.
SUPPLY: 5-6 V on pad 2. Maximum continuous current 1.8 A, 2.5 A peak, quiescent under 1 mA with no PPM signal present, so a 2 A supply is the practical floor.
LOGIC: the control line is a servo-compatible pulse train at 500 Hz with 1 us resolution, and the vendor quotes no logic-high threshold, so drive it from the same 5 V rail as the board rather than from a 3.3 V GPIO alone.
CIRCUIT: the vendor publishes no schematic for the driver board, so its internal pull-ups, gate drive and decoupling are not recorded - do not assume any. The only external wiring the vendor specifies is the 5-6 V supply on pads 2/3 and the motor on pads 4/5.
TRAPS: (1) This is a PPM (pulse-width in microseconds) input, not a PWM duty-cycle input - a 500 us positive pulse is maximum forward speed, 1400-1600 us is stop, and 2500 us is maximum reverse, so a 50-percent duty PWM signal will simply hold the pump stopped. (2) Reversing the motor is done by the pulse width, not by swapping pads 4 and 5. (3) Flow is 85 ml/min only at maximum speed; the vendor says to calibrate the fill time yourself because flow varies with tube condition. (4) Working ambient is 0-40 C at under 80 percent relative humidity.