Product Datasheet - DRV256 Fieldbus Edition

Key Features

USB CDC virtual serial bridge for the actuator serial interface
Also supports UART, RS485, and CAN as alternate host interfaces ??same data as the USB CDC virtual COM port
Host packets are forwarded to all four servo ports without protocol translation
Four servo ports with power delivery, plus four ESC ports and one 4-channel ESC port
ESC outputs use the protocol selected by the ESC Protocol Type register: PWM, DSHOT300, or DSHOT600
Provides closed-loop velocity (speed) control for ESC outputs, in addition to direct throttle control
Dual 16 V / 8 A servo power domains, each feeding two servo ports, for 256 W total available servo power
Power may enter from USB-C charger input, 24 V header, or ESC-side 5 V supply
Two onboard status LEDs: LED1 turns on at bus voltage >= 11 V, and LED2 turns on when the PC USB device is configured

Product Image

DRV256 servo control board, background removed

Interface

USB Data Input

USB Micro / SM04B

1GNDGround

2D-USB data negative

3D+USB data positive

4VBUS+5 V

Host-facing USB CDC interface. Same connector family style as the camera products.

USB-C Charge Input

USB-C / SM04B

1GNDGround

2CC1Conf channel

3CC2Conf channel

4VCCPower only

Power-only USB-C path. No USB data lines are used on this connector.

24 V Header

1VINUp to 24 V

2GNDReturn

Primary high-power input for full 256 W servo-power operation, up to 12 A.

Host Serial Interfaces ??UART / RS485 / CAN

CAN, 4-pin 2.54 mm

1GNDGround

25V+5 V

3CANHCAN bus high

4CANLCAN bus low

UART / RS485, 4-pin 2.54 mm

1RXUART receive

2TXUART transmit

3ARS485 differential A

4BRS485 differential B

CAN bus rate is fixed at 1 Mbps. UART and RS485 are fixed at 115200 bps. Data sent and received over these interfaces is identical to what is sent and received when the USB CDC virtual COM port is open.

Motion Output Ports

Molex 5045 (3-pin)

1SIGSignal (serial)

2VCCServo power

3GNDGround

1x3, 2.54 mm

1GNDGround

2VCCESC power

3SIGSignal (PWM / DSHOT300 / DSHOT600)

Servo: 4 x Molex-compatible servo ports

ESC: 4 x 1x3 2.54 mm headers or 1 x SM06B 4-channel ESC port

The 4-channel ESC port and the four single ESC ports are mutually exclusive.

Because the servos are serial (daisy-chain) devices, more than one servo can be connected to a single port ??the number of servos per port is limited only by the board's available power budget, not by port count. ACT48's 48 W rating is a peak figure; since attached motors are rarely all moving at once, actual average power draw stays well under 48 W per servo, so more servos than a naive peak-power sum would suggest can typically be run.

Brief Specification

USB Device ClassUSB CDC virtual COM port 쨌 driver-free 쨌 baud rate ignored
Alternate Host InterfacesUART 쨌 RS485 쨌 CAN
UART / RS485 RateFixed 115200 bps
CAN Bus RateFixed 1 Mbps
Servo Ports4 ports, Molex-compatible actuator connector
ESC Ports4 x 1x3 2.54 mm + 1 x SM06B 4ch ESC
Power InputUSB Micro, USB-C charge-only, 24 V / 12 A header, ESC 5 V
Servo Power2 rails x 16 V / 8 A, each shared by 2 servos
ESC ControlPWM / DSHOT300 / DSHOT600 selected per ESC
Servo ID Range0-250 when ESC IDs are reserved
ESC IDs251, 252, 253, 254
ESC Model Number0xFF
Dimensions65.6 x 23.8 x 3.5 mm

Dimensions

Specification

DRV256

Electrical And Interface Reference - Rev 1.0

Parameter	Condition / Group	Value	Unit / Note
USB And Power Inputs
USB Device Type	Host-facing port	USB CDC	Virtual serial port
USB Data Connector	Main host link	USB Micro / SM04B-GHS-TBT	Camera-compatible pinout
USB-C Connector	Power only	Charge-only input	No data path
USB-C Sideband Pins	Power-only connector	GND, CC1, CC2, VCC	Pin order
Header Input Rating	Main power header	24 / 12	V / A max
ESC Auxiliary Input	Backfeed allowed	5	V from ESC side
Alternate Host Interfaces
UART	4-pin 2.54 mm header	Fixed 115200 bps	Same payload as USB CDC
RS485	Shares UART header (A/B)	Fixed 115200 bps	Same payload as USB CDC
CAN	4-pin 2.54 mm header	Fixed 1 Mbps	Same payload as USB CDC
Servo Power Delivery
Servo Power Domains	Board internal	2 rails	Independent supply groups
Per-Rail Servo Power	One rail	16 V / 8 A	128 W
Ports Per Rail	Servo outputs	2	Each rail feeds two servo ports
Total Servo Power	All rails combined	256	W
ESC Power Delivery	ESC outputs	Not supplied	ESCs are expected to power themselves
Motion Outputs
Servo Output Count	Actuator ports	4	Molex-compatible
ESC Output Count	Single ESC ports	4	1x3, 2.54 mm headers, ESC10645 compatible
4ch ESC Output *	Shared ESC group	1	SM06B, ESC40630 compatible
ESC Output Protocol	Generated by bridge	PWM / DSHOT300 / DSHOT600	Selected per ESC by register 0x83
Mechanical
Dimensions (L x W x H)	Board only	65.6 x 23.8 x 3.5	mm

Power Routing Summary

USB data enters through the USB Micro / SM04B path. Power may enter from the USB-C charge input, the 24 V / 12 A header, or an ESC-provided 5 V rail. Servo power is actively distributed by the board, but ESC outputs are signal-only because ESC modules are assumed to source their own power.

ⓘ * Mutual Exclusion: The 4-channel ESC output and the four single ESC ports share the same ESC routing group and must not be used at the same time.

Control And Mapping

DRV256

USB CDC Bridge, Servo Broadcast, And ESC Register Support

ⓘ DRV256 is a USB CDC virtual COM port device. No baud rate setting is needed ??the transport is USB virtual serial, so the host baud rate is a placeholder only (any value works in practice).

1. USB CDC Bridge Behavior ??Host baud setting is a placeholder; transport is USB virtual serial.

Packet Path: Host virtual COM port -> USB CDC device -> board bridge -> all four servo ports in parallel.
Servo-originated packets from individual downstream devices are merged by the board and sent back upstream through the same USB CDC channel.
The bridge does not reinterpret servo packets. For standard servos it forwards the original serial frame as-is. For ESC targets it converts the command intent to the protocol selected by the ESC protocol register (`0x83`).
All servos connected to a single DRV256 must be set to the same baud rate on the servo-side serial bus. DRV256 automatically detects the connected servos' baud rate ??no manual baud rate configuration is required on the board. Only these servo-side baud rates are supported: 115200, 1 Mbps, 2 Mbps.
In addition to USB CDC, DRV256 exposes UART, RS485, and CAN as alternate host interfaces (see Interface, Page 1). Whichever interface is used, the data sent and received is identical to what is sent and received when the USB CDC virtual COM port is open ??only the physical transport differs.

The serial packet format forwarded by DRV256 follows the same protocol used by the servos themselves.
See Actuator Serial Interface.

drv256_dashboard.html is a self-contained, zero-install browser application (Web Serial API) for DRV256 development and testing. No driver installation is needed on any OS, and host baud-rate setting is irrelevant ??the transport is USB virtual serial.
After connecting, add one or more motor IDs (0??54) to track: the dashboard automatically treats IDs 251??54 as ESC targets and all other IDs as standard servos, reading back each tracked motor's Position, Velocity, Current, Torque, Voltage, and Temperature as live line-graph subplots. A built-in packet builder lets you pick a command (READ / WRITE / ADD / COMMIT / ABORT and their *_WITH_ACK variants), target ID list, and register address/value, and assembles the resulting frame in a raw hex editor with byte-by-byte syntax highlighting, live validation, CRC auto-fix, and one-click send ??plus a System/RX log of all traffic.
See DRV256 Dashboard.

2. ID And Model Number Allocation

Device Class	Model Number	ID Range	Description
Standard servo *	Product-specific	0-250	Available range when the USB Servo Driver reserves the upper IDs for ESC outputs.
ESC channel 1	0xFF	251	Mapped to ESC output 1
ESC channel 2	0xFF	252	Mapped to ESC output 2
ESC channel 3	0xFF	253	Mapped to ESC output 3
ESC channel 4	0xFF	254	Mapped to ESC output 4

* Using DRV256 reduces ACT48's usable ID range to 0-250.

ESC Control Table

DRV256

Nonvolatile And Volatile ESC Register Subset

3. ESC Control Table

ESC endpoints on DRV256 do not follow the actuator serial document's full servo control table. For ESC IDs 251 through 254, use the ESC-specific control table below. The bridge accepts the same packet format on USB CDC and selects PWM, DSHOT300, or DSHOT600 from register 0x83. Register 0xD1 controls the corresponding ESC LED through AM32 DShot commands 22..29; the command is sent only after the ESC has received stop frames. Register 0xC9 changes the ESC's persistent direction setting using DSHOT commands 7/8 followed by save command 12. A negative throttle temporarily reverses direction only on DSHOT endpoints, using command 20 or 21 without modifying 0xC9; PWM input is always unidirectional and clamps negative commands to its minimum pulse. bDShot extended telemetry is enabled only after eight stop frames and the command-13 repeat sequence has completed. If an ESC that had supplied extended telemetry stops replying for 4 s, the bridge latches the telemetry-stale error and disarms that endpoint. The two DRV256 board LEDs are independent of ESC register 0xD1: LED1 indicates bus voltage >= 11 V, and LED2 indicates that the PC USB device is configured.

3-1. Nonvolatile Area ??persistent across power cycles

Addr	Type	Name	Access	Default	Description
0x80	u8	Model Number	R	0xFF	Always reads as 0xFF.
0x81	u8	Firmware Version	R	Varies	ESC firmware revision exposed through the bridge.
0x82	u8	ID	R	251-254	Fixed to 251, 252, 253, or 254 depending on ESC channel.
0x83	u8	Protocol Type	R/W	1	0 = PWM, 1 = DSHOT300, 2 = DSHOT600.
0x84	u8	Return Delay Time	R/W	250	Return delay in 2 us units before the bridge returns an ESC read or ACK response.
0x85	u8	Operating Mode	R/W	0	0x00 = Throttle, 0x01 = Current, 0x02 = Velocity. Position and Extended Position modes are not available for ESC endpoints.
0x8E	u8	Temperature Limit	R/W	80	When telemetry reaches this threshold, the bridge reduces the output throttle ceiling by 1% per second until temperature falls below the limit.
0x8F	u16	Max Voltage Limit	R/W	16000	Upper supply limit; crossing it latches the hardware-error flag but does not derate output.
0x91	u16	Min Voltage Limit	R/W	5000	Lower supply limit; low voltage derates output by 1% per second and disarms after 100 seconds continuously below the limit.
0x93	u16	Current Limit	R/W	3000	When valid bDShot current telemetry reaches this value, output throttle is reduced by 1% per second and the hardware-error flag is latched.
0x95	i16	Max Velocity Limit	R/W	32767	Non-negative maximum RPM magnitude. When exceeded, the bridge reduces the output throttle ceiling by 1% per second until RPM falls below this limit. The default is INT16_MAX; 0 is a valid limit and permits only zero measured RPM. Negative values are invalid and latch the hardware-error flag.
0xB1	u16	PWM Min	R/W	1000	Minimum PWM pulse width in microseconds when the ESC protocol is 0 (PWM).
0xB3	u16	PWM Max	R/W	2000	Maximum PWM pulse width in microseconds when the ESC protocol is 0 (PWM).
0xB5	u16	PWM Timeout	R/W	10000	If raw throttle input has no new command for this many microseconds, the PWM output falls to PWM Min; 0 disables the timeout. PWM input is always unidirectional.
0xBD	u16	Velocity P Gain	R/W	0	Closed-loop velocity proportional gain; gain scale is 1/1024.
0xBF	u16	Velocity I Gain	R/W	0	Closed-loop velocity integral gain; gain scale is 1/1024.
0xC1	u16	Velocity D Gain	R/W	0	Closed-loop velocity derivative gain; gain scale is 1/1024.
0xC3	u16	Current P Gain	R/W	0	Current-to-throttle proportional gain; gain scale is 1/1024.
0xC5	u16	Current I Gain	R/W	0	Current-to-throttle integral gain; gain scale is 1/1024.
0xC7	u16	Current D Gain	R/W	0	Current-to-throttle derivative gain; gain scale is 1/1024.
0xC9	u8	Reverse Direction	R/W	0	0 = normal spin direction; 1 = reversed spin direction. On DSHOT endpoints the bridge applies this through the ESC's persistent direction setting and save command. A negative raw/current/velocity command temporarily reverses relative to this setting without changing it. PWM endpoints ignore direction and remain unidirectional.
0xCA	u16	Current Anti-Windup Shift	R/W	3	Integral decay shift at current-PID saturation. Smaller values unwind faster; valid effective range is 1-15.
0xCC	u16	Velocity Anti-Windup Shift	R/W	3	Integral decay shift at velocity-PID saturation. Smaller values unwind faster; valid effective range is 1-15.

ESC Control Table

DRV256

Volatile ESC Register Subset

3-2. Volatile Area ??resets to initial value on power-up

ESC endpoints reject unsupported addresses normally; in particular 0x97-0x9C and 0xE6-0xE7 are not part of the ESC register map.

Addr	Type	Name	Access	Initial	Description
0xD0	u8	Torque Enable	R/W	0	Mapped to ESC arming state.
0xD1	u8	ESC LED	R/W	0	Supported on ESC IDs 251..254. The bridge maps these IDs to AM32 DShot LED0..LED3 and sends commands 22..25 for ON or 26..29 for OFF. The command is deferred until the ESC is stopped.
0xD4	u8	Hardware Error Status	R	0	Latched error mask: bit 0 = overcurrent, bit 1 = overtemperature, bit 2 = voltage limit, bit 3 = unsupported PWM operating mode, bit 4 = bridge queue/transport overrun, bit 5 = stale bDShot telemetry, bit 6 = invalid ESC/PWM configuration. Bits remain set until reboot.
0xD5	u8	Moving	R	0xFF	Valid only while bidirectional DSHOT telemetry is available. 0xFF means unsupported or unavailable.
0xD6	i16	Goal Current	R/W	0	Signed target current in mA. It is used only in Operating Mode 1; other ESC modes ignore this register. On DSHOT, a negative target requests the temporary reverse direction.
0xD8	i16	Goal Velocity	R/W	0	For ESC endpoints this is a speed target in RPM, not the 0.1 deg/s unit used by standard servos. It is used only in Operating Mode 2; a negative target requests temporary reverse on DSHOT.
0xE8	u16	Present Current	R	-1	ESC input current in mA. Standard EDT type 0x06 remains whole amperes. ESCLITE sends type 0x08 first: bits 0..6 carry the 0.01 A remainder and bit 7 carries the extra 0.125 V voltage step. The driver caches that extension, commits current when the following 0x06 arrives, and commits voltage when the following 0x04 arrives. This gives 10 mA current resolution while a generic FC may continue to read 0x06 as whole amperes and ignore 0x08 as device-specific debug. The u16 driver register saturates at 65535 mA.
0xEA	i16	Present Throttle	R	0	Present throttle command, in 4096-step units. For ESC endpoints this reflects drive strength, not the power-based torque measurement used by standard servos.
0xEC	i16	Present Velocity	R	-1	Present shaft velocity in RPM. Requires valid bidirectional DSHOT telemetry; -1 means unsupported or unavailable.
0xF6	u16	Present Input Voltage	R	-1	Present supply voltage from extended bidirectional DSHOT telemetry, in mV. Standard EDT type 0x04 remains 0.25 V/LSB; ESCLITE sends its type 0x04 after the 0x08 extension and adds 0.125 V when bit 7 of that cached field is set. The DRV256 therefore exposes 125 mV resolution. Update rate is determined by the ESC firmware's extended telemetry scheduler. -1 means unsupported or unavailable.
0xF8	u8	Present Temperature	R	-1	ESC temperature from extended bidirectional DSHOT telemetry, in degrees C. -1 means unsupported or unavailable.
0xF9	i16	Raw Throttle / Present PWM	R/W	0	Raw throttle command in Operating Mode 0. On PWM endpoints it is always unidirectional: 0 maps to PWM Min, positive values linearly map to PWM Max, and negative values clamp to PWM Min. A nonzero operating mode forces minimum output and latches the unsupported-mode error.

Fieldbus Bridge

DRV256

Modbus RTU and CANopen over the native actuator serial core

Host Interface Rules

USB CDC and host UART keep the original actuator serial protocol unchanged.
RS485 is a Modbus RTU slave interface at 115200 bps, 8N1.
CAN is a Classical CAN 2.0A interface at 1 Mbit/s with a compact CANopen CiA 402 subset.
Both fieldbus interfaces translate host requests into actuator serial packets internally.
The bridge emits translated serial packets only on servo ports where the target servo ID was found during scan.
Duplicate servo IDs are allowed on the native serial path (USB CDC / host UART), but are not allowed on RS485 Modbus RTU or CANopen. Fieldbus access is rejected if one servo ID is found on multiple servo ports.
Servo-side firmware remains serial-only. No Modbus RTU or CANopen parser runs inside the servo.

Protocol Scope

Bus	Implemented Host View
USB CDC	Native actuator serial packets, unchanged
UART	Native actuator serial packets, unchanged
RS485	Modbus RTU slave with motion-oriented holding registers
CAN	CANopen with SDO access to CiA 402 style control objects and basic RPDO/TPDO exchange

Translation Path

Host Modbus RTU or CANopen request
↓
DRV256 firmware fieldbus parser
↓
Internal serial packet builder
↓
Port-selective single-wire servo packet transmission

RS485 / Modbus RTU Map

Default slave address = servo_id + 1. Supported function codes: 03h, 06h, 10h.

Register	Type	Meaning	Access	Internal Serial Mapping
0x0000	u16	Controlword	R/W	0xD0 Torque Enable. Standard CiA 402 values 0x0006, 0x0007, 0x000F are accepted; only 0x000F asserts torque.
0x0001	u16	Statusword	R	Bridge shadow: 0x0040 switch-on disabled, 0x0021 ready to switch on, 0x0023 switched on, 0x0027 operation enabled.
0x0002	u16	Operating Mode	R/W	0x85 control mask. CANopen values 10 torque, 3 velocity, and 1 position translate to native masks 1, 2, and 4.
0x0010	i16	Target Torque	R/W	0xD6-0xD7
0x0011	i16	Target Velocity	R/W	0xD8-0xD9
0x0012-0x0015	i64	Target Position	R/W	0xDA-0xE1
0x0020	i16	Present Torque	R	0xEA-0xEB
0x0021	i16	Present Velocity	R	0xEC-0xED
0x0022-0x0025	i64	Present Position	R	0xEE-0xF5
0x0026	u16	Bus Voltage	R	0xF6-0xF7
0x0027	u8	Temperature	R	0xF8
0x0030	u16	Profile Velocity	R/W	0xE6-0xE7; standard-servo endpoints only, unsupported by ESC endpoints.
0x0031	u16	Current Limit	R/W	0x93-0x94

CAN / CANopen Object Subset

Node-ID = servo_id + 1. SDO and a compact PDO set are supported. Target objects are translated into actuator serial packets internally. RPDO1 carries 6040h and optionally 6060h; RPDO2 payload interpretation follows the currently selected mode.

Index	Type	Meaning	Access	Internal Serial Mapping
6040h	u16	Controlword	R/W	0xD0 Torque Enable. 0x0006, 0x0007, 0x000F map to the compact CiA 402 state subset; only 0x000F enables torque.
6041h	u16	Statusword	R	Compact CiA 402 shadow: 0x0040, 0x0021, 0x0023, 0x0027.
6060h	i8	Modes of Operation	R/W	0x85 Operating Mode Mask. Supported CANopen values: 10 torque → native 1, 3 velocity → 2, 1 position → 4.
6061h	i8	Modes Display	R	Bridge shadow using the same 10/3/1 values.
6071h	i16	Target Torque	R/W	0xD6-0xD7
60FFh	i32	Target Velocity	R/W	0xD8-0xD9, sign-extended
607Ah	i32	Target Position	R/W	0xDA-0xE1, sign-extended from 32-bit host value
6077h	i16	Actual Torque	R	0xEA-0xEB
606Ch	i32	Actual Velocity	R	0xEC-0xED, sign-extended
6064h	i32	Actual Position	R	0xEE-0xF5, truncated/clamped to 32-bit
6081h	u32	Profile Velocity	R/W	0xE6-0xE7; standard-servo endpoints only, unsupported by ESC endpoints.
1017h	u16	Producer Heartbeat Time	R	Bridge-local heartbeat timer

Pricing

DRV256

Standard Unit Pricing - Rev 1.0

Part Number Naming Rule

DRV USB Servo
Driver

256 Power
Rating (W)

-

x Country

Prefix

DRVUSB Servo Driver

Power Rating

256Maximum 256 W total servo power

Country of Origin

CChina

KKorea

XUnspecified

Sample Unit Pricing - DRV256 Series

Listed price is for a representative sample unit. Volume pricing available on request.

Part Number	Description	Qty	Unit Price
DRV256-X	256 W USB Servo Driver, country unspecified	1 pcs	US$ 50

ⓘ Volume pricing available for orders of 10 units or more - contact us for a quote. ✉ hyon646@gmail.com

How to Order

Select your model using the Part Number Naming Rule above and specify the Country of Origin option when placing an order.

Lead Time (stock)	1-3 business days
Lead Time (order)	4-6 weeks
Minimum Order Qty	1 pcs (standard) - 10 pcs (volume)
Payment	PayPal - Bank Transfer - Other (on request)
Shipping	Worldwide - DHL / FedEx / EMS
Contact	hyon646@gmail.com

Document Revision History

Version	Date	Description
v1.0	2026-07-03	Initial Release

ProductDatasheet

Specification

Control And Mapping

ESC Control Table

ESC Control Table

Fieldbus Bridge

Pricing

Product
Datasheet