DCC-EX Motor Shield

Overview

The DCC-EX Motor Shield is based on two H-bridge motor drivers with integrated current sensing feedback to drive inductive loads like relays, solenoids, DC and stepping motors. It is based on the DRV8874 from Texas Instruments (TI).

Powering of Arduino boards is possible due to the on board DCDC buck converter supporting a wide input supply range from 9 to 30V. The reverse polarity protection prevents damage to the circuit and its components in case the power supply is accidentally connected with reversed polarity.

This DCC-EX Motor Shield features a status LED for supply, which provides a visual indication of the power supply status.

Compatibility with Arduino Motor Shield Rev3

The DCC-EX Motor Shield is pin compatible with the original Arduino Motor Shield but provides significantly improved electrical performance for driving higher loads. The supply voltage range is 9-30V (instead of 5-12V) and the maximal peak current is 5A per channel (instead of 2A).

Availability

If you don't want to manfacture the Motorshield by yourself you can directly order fully assembled Motorshields at semify.

Pin Assignment for motor control

The DCC-EX Motor Shield has the following pin assignment for the Arduino header

Default pin assignment (DRV8874 mode select pin PMODE = high) in PWM motor control mode.

Function	Pin
Channel A
Direction	D12
PWM	D3
Brake	D9
Fault_N	A4
Current sensing	A0
Channel B
Direction	D13
PWM	D11
Brake	D8
Fault_N	A5
Current sensing	A1

Alternative pin assignment for motor control

The alternative pin assignment for motor control (PH/EN mode) allows to control the motor in a speed and direction type interface. This mode is selected via Jumper J101 (DRV8874 mode select pin PMODE = low).

TBD fix table

Function	Pin
Channel A
EN	D12
PH	D3
Brake	D9
Fault_N	A4
Current sensing	A0
Channel B
Direction	D13
PWM	D11
Brake	D8
Fault_N	A5
Current sensing	A1

Fault indicator

The H-Brides are prodeted against supply undervoltage, charge pump undervoltage, output overcurrent and device overtemperature. Fault conditions are indicated on the pin nFAULT of the H-Bridge driver. The open drain output of the fault indicator is pulled low during a fault condition and pulled to high with the on board pull-up resistor. There is one fault indicator per channel.

Alternative pinout for motor control  

All motro control signals can be connected to two different Adruino header pins. Selecting between the default pin out and the alternative pin out is done via solder jumper on the PCB.

Function	Pin
Channel A
Direction	D10
PWM	D2
Brake	D7
Fault_N	D0
Current sensing	A2
Channel B
Direction	D4
PWM	D5
Brake	D6
Fault_N	D1
Current sensing	A3

Parameter

The DCC-EX Motor Shield provides the following electrical parameters.

Parameter	Value
Operating voltage range	9-30V
Maximal current	5A peak
Arduino supply voltage output (VIN)	7.2V
IO voltage	3.3 and 5V
I2C connectivity	Dupont and STEMMA QT Headers
Current sensing	Yes
Control modes (selected via jumper)	PH/EN, PWM

Current sensing

Current sensing is independently available for each channel. The VDDIO supply voltage sensing automatically adjusts the gain factor for the current sensing to take advantage of the full ADC input voltage range. The translation factor is 4.82 A/V.

Track LEDs

TBD

Stacking multiple boards

It is possibile to stack two DCC-EX Motor Shields. There are two different operating modes possible.

1. Parallel mode: The DCC-EX Motor Shields controlled with the same control signals and both H-bridges are running in parallel. This mode is used to increase the current capabilities.
2. Independent mode: The DCC-EX Motor Shields controlled independently using different control signals. This allows to drive in total 4 independent H-Bridges completely independently.

The independent mode uses the following pin assignment for controlling the two channels of the second DCC-EX Motor Shield

Header

Arduino Header

Expansion Header

Two I2C expansion headers (Dupont and STEMMA QT) allow connecting either an OLED display or other additional I2C based devices.

Function	Pin
SCL	A5
SDA	A4

Pull-up resistors for the I2C communication are not assembled by default. If required pull-up resistors can be assembled (R101, R102).

Reset button

To reset the Arduino board a reset button is available.

Reference

• Schematic
• DRV8874 Datasheet