Communication Protocols

ASI BAC controllers support multiple communication protocols for configuration, monitoring, and network control.

Available Protocols

CANopen Protocol

Overview

CANopen is the primary network protocol for BAC controllers, enabling:

• Remote motor control
• Real-time telemetry
• Multi-device networks
• Parameter configuration

Critical Timeout Parameters

Three essential parameters ensure reliable operation:

Watchdog Counter Implementation

A rolling counter mechanism is required for reliable operation:

You must send a rolling counter on the high byte of Remote state command on a heartbeat within the timeout thresholds.

Remote State Command Format:

Send heartbeat at 100ms intervals with incrementing counter.

Fault Behaviors

Network Communication Timeout (Fault bit 8)

• Trigger: Communication loss exceeding timeout
• Behavior: Disables motor until power cycle
• LED Flash: 2-1 sequence

Communication Loss Braking

Activates only in remote speed mode with serial stream control:

• Limits braking current to Remote comm loss braking current
• Duration: 10 seconds maximum

Local Mode Operation

When using throttle input locally, prevent timeout faults by:

• Sending heartbeat counter above 255 (0x0100 to 0xFF00 range)
• Maintaining heartbeat within timeout thresholds

PDO Configuration

TPDO (Transmit PDOs)

Broadcast timing is configurable per application requirements.

RPDO (Receive PDOs)

Configure RPDO timing to match your network's sync rate to avoid CAN Sync Loss faults.

Remote Control Modes

Speed Mode (Regulator Mode 0)

Torque Mode (Regulator Mode 1)

No speed control - motor spins based on applied current:

Torque with Speed Limiting (Mode 2)

Combines torque and speed parameters:

• Requires complementary sign alignment
• Speed limits torque application

Current Limits

Both modes require setting:

Regen via Network

To control regen braking via CAN:

1. Set Regen brake source to "Network"
2. Configure Remote Maximum Braking Current
3. Send braking commands via Remote torque command (negative values)

Priority (Firmware 6.014+): When both engine braking and network regen are active, the controller applies whichever commands higher braking torque.

MODBUS Protocol

Overview

MODBUS provides simpler serial communication for basic control and monitoring.

Key Resources

• Protocol Document: ASI Modbus Protocol Rev 1.22 (PDF)
• CRC Calculation: Use CRC16 - Modbus specifically

Implementation

Refer to the ASI Modbus Protocol document for:

• Register mappings
• Function codes
• Message formatting
• Error handling

TTL Serial Communication

Connection

Usage

• Direct connection to BACDoor software
• Parameter configuration
• Real-time monitoring
• Firmware updates

Display Integration

Supported Protocols

Configuration Steps

1. Activate Communications configuration vector bit 10 (Enable Ebike)
2. Select appropriate display protocol
3. Set assist mode source to display
4. Configure walk mode signal source
5. Input wheel diameter and speed sensor parameters

Wiring Options

Network Telemetry

Available Data

Real-time parameters accessible via network:

Fault/Warning Registers

TPDO Timing

Configure broadcast intervals based on:

• Network bandwidth
• Required update rate
• Number of devices

CAN Bus Hardware

Termination

CAN bus requires 120Ω termination resistors at each end:

• BAC controllers have configurable internal termination
• Total bus resistance should measure ~60Ω between CAN-H and CAN-L

Testing

1. Measure resistance between CAN-H and CAN-L
2. Expected: ~60Ω with two terminators
3. Use PEAK CAN dongle with PCAN viewer for traffic analysis

Configuration Checklist

CANopen Setup

MODBUS Setup

1. Configure baud rate
2. Set device address
3. Verify CRC implementation (CRC16-Modbus)
4. Test register read/write operations

Next Steps

• Configure Software Tools for monitoring
• Review Protection Systems for fault handling
• Check Technical Q&A for common questions