Arduino RS-485 Modbus RTU driver for StepperOnline BLD-510B and BLD-510S BLDC motor controllers.
- Supports StepperOnline BLD-510B and BLD-510S drivers.
- Uses Modbus RTU over RS-485 with any Arduino
Streamobject, including hardware serial and software serial. - Handles the BLD-510x speed-register byte-order quirk from the manual examples.
- Supports run, stop, braking stop, direction, speed, acceleration/deceleration, speed feedback, address selection, and fault reads.
- Optional TX/RX frame logging for bring-up and troubleshooting.
You need an RS-485 transceiver between the microcontroller serial port and the motor driver. Pass the serial object and transceiver DE/RE direction-control pin to the constructor.
Typical wiring:
- MCU TX -> RS-485 transceiver DI
- MCU RX -> RS-485 transceiver RO
- MCU direction pin -> transceiver DE and /RE control
- Transceiver A/B -> BLD-510x RS-485 A/B
- Common ground between controller and driver, unless your interface is intentionally isolated
RS-485 transceiver option:
Any equivalent half-duplex RS-485 transceiver should work if it exposes UART RX/TX plus driver/receiver enable control pins compatible with your microcontroller voltage.
Initialize the serial object in your sketch before calling motor.begin(). Default driver serial settings are:
- 9600 baud
- 8 data bits
- no parity
- 1 stop bit
Clone or download this repository into your Arduino libraries folder:
Documents/Arduino/libraries/BLD510x
Restart the Arduino IDE, then open:
File > Examples > BLD510x > BLD510x_example
Use the repository as a library dependency:
lib_deps =
https://github.com/ShadyLogic/BLD510x.gitOr copy this repository into your project's lib/BLD510x folder.
#include <BLD510x.h>
constexpr uint8_t RS485_DE_RE_PIN = 2;
BLD510x motor(Serial1, RS485_DE_RE_PIN, 1);
void setup()
{
Serial.begin(115200);
Serial1.begin(9600, SERIAL_8N1);
motor.begin();
motor.setResponseTimeout(150);
motor.setPolePairs(2);
motor.setMaxRPM(7000.0f);
motor.setAccelerationDeceleration(10, 10);
motor.runRPM(1500.0f, BLD510x::Forward);
}
void loop()
{
float rpm = 0.0f;
if (motor.getRPM(rpm))
{
Serial.print("Motor RPM: ");
Serial.println(rpm);
}
if (motor.hasFault())
{
motor.printFault(Serial);
motor.emergencyBrake();
}
delay(500);
}The BLD-510B and BLD-510S use the same Modbus command structure for the functions implemented by this library.
Supported commands/registers include control, speed setting, acceleration/deceleration, driver address, actual speed feedback, and fault state.
Enable frame logging when wiring or verifying RS-485 communication:
motor.setDebugStream(&Serial);This prints transmitted and received Modbus frames in hex.
See examples/BLD510x_example/BLD510x_example.ino for a fuller bring-up sketch that demonstrates:
- setup command checks
- response timeout configuration
- optional frame logging
- forward/reverse run
- speed changes
- natural stop
- braking stop
- speed feedback
- fault handling
The speed command register is intentionally written with little-endian value bytes because the BLD-510B and BLD-510S manual examples show values such as 1000 RPM as E8 03 and 1500 RPM as DC 05. Register addresses and CRC bytes still follow normal Modbus RTU ordering.
Test unloaded first. Verify motor direction, stop/brake behavior, fault handling, and any external emergency-stop hardware before attaching the motor to mechanics. A serial command or wiring mistake can start motion unexpectedly.
MIT License. See LICENSE.