motor_params/AD_Keil_Project/AD_docs/BINARY_TRANSPORT.md

Binary Telemetry Transport

The firmware initializes two physical transports for the existing binary telemetry packet:

• USB FS CDC ACM on PA11/PA12, clocked from HSI48.
• FDCAN1 classic CAN on PB8/PB9, default 500 kbit/s with an external CAN transceiver.

Modbus RTU on USART2 remains active as the control channel. This is intentional: the host can always switch the telemetry mode back without reflashing.

Modbus Selection Registers

Modbus protocol/register-map version is 7.

Address hex / dec	Field	Access	Purpose
0x001C / 28	H028_control_host_protocol	R/W	0=Modbus control only, 1=binary telemetry output enabled
0x001D / 29	H029_control_binary_transport	R/W	0=USB CDC, 1=CAN/FDCAN1, 2=USB CDC and CAN

USB CDC

USB is exposed as a CDC ACM serial stream. The stream does not guarantee message boundaries, so the PC side should parse by the telemetry header:

• magic
• payload_size
• sequence
• crc16

CAN/FDCAN

CAN carries the same binary packet split into classic 8-byte frames:

Standard ID	Payload
0x5A0	packet bytes 0..7
0x5A1	packet bytes 8..15
0x5A2	packet bytes 16..23

The base standard ID is controlled by AD_CAN_TELEMETRY_STD_ID_BASE, default 0x5A0. The receiver reconstructs the packet from sequential frame IDs and uses the normal binary telemetry header to determine the full packet length.