CAN-bus
The communication between the electronics within the solar boat is build upon the CAN-bus protocol, where the datalogger logs the CAN messages. Every CAN-frame holds data that is PCB specific build, these frames are built according the CANOpen protocol.
CANopen format
A CAN-frame consists of an 11-bit identifier, a 1-bit Remote Transmission Request (RTR), 4-bit data length of the message and up to 8 bytes of data.
| CAN-ID | RTR | Data length | Data | |
|---|---|---|---|---|
| Length | 11 bits | 1 bit | 4 bits | 0-8 bytes |
The default CAN-ID mapping sorts frames by attributing a function code (NMT, SYNC, EMCY, PDO, SDO) to the first 4 bits, so that critical functions are given priority.
| Function code | Node ID | |
|---|---|---|
| Length | 4 bits | 7 bits |
The data bytes are split into the following components:
| Data[0] | Data[1] | Data[2] | Data[3] | Data[4] | Data[5] | Data[6] | Data[7] |
|---|---|---|---|---|---|---|---|
| Node-ID | Index Low | Index High | Subindex | Data | Data | Data | Data |
Following the format the specific subsystems within the solar boat are given here below in their respective section.
Battery (MG) CAN-format
As of now the MG electronics battery is used in the solar boat. Although a new battery is being developed, this MG battery is still in use (as of September '22). Therefore the battery format is given here below.
| Node-ID | Index | Subindex | Data | Type | Resolution |
|---|---|---|---|---|---|
| 0x302 | 0x2005 | 0x01 | Voltage [V]
|
uint16_t | 1 [mV/LSB]
|
| 0x02 | Current [A]
|
int16_t | 10 [mA/LSB]
| ||
| 0x03 | Current Discharge [A]
|
int16_t | 10 [mA/LSB]
| ||
| 0x04 | Current Charge [A]
|
int16_t | 10 [mA/LSB]
| ||
| 0x05 | State-of-Charge [%]
|
int8_t | 1 [%/LSB]
| ||
| 0x06 | |||||
| 0x07 | Time to Go [min]
|
uint16_t | 1 [min/LSB]
| ||
| 0x402 | 0x2005 | 0x09 | Cell Temperature High [°C]
|
int8_t | 1 [°C/LSB]
|
| 0x0A | |||||
| 0x0B | Cell Temperature Low [°C]
|
int8_t | 1 [°C/LSB]
| ||
| 0x0C | Cell Voltage High [V]
|
uint16_t | 1 [mV/LSB]
| ||
| 0x0D | Cell Voltage Low [V]
|
uint16_t | 1 [mV/LSB]
| ||
| 0x0E | BMS State | uint32_t | |||
| 0x0F | Temperature Collection [°C]
|
4x uint8_t | 1 [°C/LSB]
| ||
| 0x482 | 0x2000 | Cell nr | Cell [Cell_nr] Voltage [V]
|
uint16_t | 1 [mV/LSB]
|
| 0x202 | Don't Care | Don't Care | Power Level [%]
|
uint8_t | 1 [%/LSB]
|
MPPT CAN-format
MPPT CAN-ID is set on the PCB with 3 resistors, ID 0-7. In case of the MPPT a formula needs to be used to determine the Node-ID of the respective MPPT.
The following formula needs to be used:
can_base_id = 1254 + (device_id * 8)
The CAN-data is in HEX therefore can_base_id needs to be converted to a hexadecimal value: Node-ID.
| Node-ID | Index | Subindex | Data | Type | Resolution |
|---|---|---|---|---|---|
| 0x4E6 + (device_id * 8) | Don't Care | 0x00 | Voltage Output [V]
|
int16_t | |
| 0x01 | Current Output [A]
|
int16_t | |||
| 0x02 | Voltage OUT_SW [V]
|
int16_t | |||
| 0x03 | MPPT State | uint8_t | |||
| 0x04 | Safety Enabled | bool | |||
| 0x05 | PWM Enabled | bool | |||
| 0x06 | Temperature [°C]
|
int8_t | 1 [°C/LSB]
| ||
| 0x4E6 + (device_id * 8) | Don't Care | 0x08 | Voltage Panel 1 [V]
|
int16_t | |
| 0x09 | Current Panel 1 [A]
|
int16_t | |||
| 0x0A | Voltage Panel 2 [V]
|
int16_t | |||
| 0x0B | Current Panel 2 [A]
|
int16_t | |||
| 0x0C | Voltage Panel 3 [V]
|
int16_t | |||
| 0x0D | Current Panel 3 [A]
|
int16_t | |||
| 0x0E | Voltage Panel 4 [V]
|
int16_t | |||
| 0x0F | Current Panel 4 [A]
|
int16_t | |||
| 0x4E6 + (device_id * 8) | Don't Care | 0x01 | Duty Cycle Panel 1 [%]
|
uint8_t | 1 [%/LSB]
|
| 0x02 | Duty Cycle Panel 2 [%]
|
uint8_t | 1 [%/LSB]
| ||
| 0x03 | Duty Cycle Panel 3 [%]
|
uint8_t | 1 [%/LSB]
| ||
| 0x04 | Duty Cycle Panel 4 [%]
|
uint8_t | 1 [%/LSB]
| ||
| 0x05 | Channel Active map | 4x uint8_t |