SPP CAN Communication Protocol breaf introduction
1.Network topology description
SPP Smart Battery – UAV (Drone)
The protection board adopts CAN interconnection structure in the drone network, and the CANBUS is the data communication bus between the protection board (BMS) and the flight control system (FCS).
The R is 120Ω terminal resistance.
2. CAN communication protocol data format
The CAN network signal data format follows the table below, and the two-line definition follows the first line
3. Communication specification
3.1 Principles to be followed at the data link layer
The bus communication rate is:
500Kbps. The regulations of the data link layer mainly refer to the relevant regulations of CAN2.0B and SAE J1939.
The 29-bit identifier of the CAN extended frame is used and redefined.
The following is the allocation table of the 29-bit identifier:
Among them, the priority is 3 bits, there can be 8 priority levels, R is generally fixed to 0, DP is now fixed to 0, 8-bit PF is the message code, 8-bit PS is the target address or group extension, 8-bit SA is the source address to send this packet.
Each node in the access network has a PGN and an address.
The PGN is used to identify the function of the node and perform address arbitration.
The address is used for data communication of the node.
Each node has at least one function, and multiple nodes may have the same function, or a node may have multiple functions.
For multi-byte data, use the little-endian method, such as 4660=0x1234, send 0x34 first, then send 0x12.
3.2 CAN network address allocation table
|Node name address||SOURCE ADDRESS(SA)|
3.3 Hardware requirements for CAN Communication Protocol
a. The CAN of the BMS network system is not physically isolate from the battery pack.
b. The network system supports hot-swap, the power supply should have reverse connection protection and power failure detection function.
c. The communication cable of the CAN bus uses twisted pair.
d. The farthest parts on the CAN bus must have termination resistance (120Ω).
e. The CAN communication cable should do its best to leave the power line.
4. Protocol message
4.1 BMS send FCS message 1
4.2 BMS send FCS message 2
4.3 BMS send FCS message 3
4.4 BMS send FCS message 4
4.5 BMS send FCS message 5
4.6 BMS send FCS message 6