This is an alternative firmware for the Longan Serial Can Bus Module. The original firmware can be found on github.
The UART is configured to run at 9600 baud by default, but this can be changed using a command.
Any of the commands in the table below can be sent.
Each command must be terminated by a \n character.
The response of a command may consist of one or more lines, each terminated by a \n.
The final response line of a command is always OK if the command succeeded, or ERROR: <code> when an error occured.
The following commands are available:
Prints the version of the firmware.
Command:
VERSION?
Response:
<version>
| Field | Description |
|---|---|
version |
A number describing the firmware version |
Example:
VERSION?
002
OK
Enables or disables the echo.
Command:
ECHO=<sate>
| Parameter | Description |
|---|---|
state |
0 when echo should be disabled, 1 when echo should be enabled. |
Gets whether commands are echoed or not.
Command:
ECHO?
Response:
<state>
| Field | Description |
|---|---|
state |
Is 1 if commands are echoed, 0 if commands are not echoed. |
Sets the baud rate of the serial port.
Command:
BAUD=<baud>
| Parameter | Description |
|---|---|
baud |
The desired baud rate. Possible values are: 9600, 115200. |
Gets the current baud rate of the serial port.
Command:
BAUD?
Response:
<baud>
| Field | Description |
|---|---|
baud |
The current baud rate of the serial port. |
Sets the speed of the CAN bus.
Command:
SPEED=<speed>
| Parameter | Description |
|---|---|
speed |
The speed of the CAN bus in kilobits per second. Possible values are: 5, 10, 20, 25, 31, 33, 40, 50, 80, 83, 95, 100, 125, 200, 250, 500, 666, 1000 |
Gets the current speed of the CAN bus.
Command:
SPEED?
Response:
<speed>
| Field | Description |
|---|---|
speed |
The speed of the CAN bus. |
Reads a register from the MCP2515.
Command:
READREG=<address>
| Parameter | Description |
|---|---|
address |
A hexadecimal value between 0 and FF. A register at this address will be read from the MCP2515. |
Response:
<value>
| Field | Description |
|---|---|
value |
A hexadecimal value between 0 and FF. This is the value returned by the MCP2515. |
Example:
READREG=29
f0
OK
Writes to a register of the MCP2515.
Command:
WRITEREG=<address>,<value>
| Parameter | Description |
|---|---|
address |
A hexadecimal value between 0 and FF. To the register at this address will the data be written. |
value |
A hexadecimal value between 0 and FF. The value that will be written to the register. |
Reads the next frame in the buffer.
Command:
READ
Response:
<id>,<length>,<data>
| Field | Description |
|---|---|
id |
The ID to which the message was sent. |
length |
The number of bytes of data that were received. |
data |
The data that was encoded within the can message. It is encoded in hexadecimal, and contains between 0 to 8 bytes of data. |
Example:
READ
120,3,414243
OK
Gets the number of frames currently in the buffer.
Command:
READ?
Response:
<count>
| Field | Description |
|---|---|
count |
The number of packets currently stored in a buffer. |
Sends a CAN message.
Command:
WRITE=<id>,<length>,<data>
| Parameter | Description |
|---|---|
id |
The ID of the CAN message. |
length |
The number of bytes to send. |
data |
The data to send. This should be encoded in hexadecimal. |
Example:
WRITE=121,2,410a
OK
The following error codes can be returned by the firmware:
| Error Code | Description |
|---|---|
| 1 | An unknown command was executed. |
| 2 | A parameter was given an invalid value. |
| 3 | The baud rate specified is invalid or not supported. |
| 4 | The CAN bus speed specified is invalid or not supported. |
| 5 | The register address to read from is invalid. |
| 6 | The value to write to the register is invalid. |
| 7 | No CAN frames available for reading. |
| 8 | The speed of the MCP2515 could not be set. |