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SMU-Communication-Backend

The Communication Backend for the Universal-I2C-Sensor-Master-Unit.

General Message Formate

All serial messages used to controll the SMU board follow the following format:

|-----------------|-------------|-------------|----------------------|----------|-----------------|
| '~' as Preambel | MessageType | PayloadSize | 0 - 25 Bytes of Data | Checksum | '#' as End-Sign |
|      1 Char     |   1 Byte    |    1 Byte   |     0 - 25 Bytes     |  1 Byte  |      1 Char     |
|-----------------|-------------|-------------|----------------------|----------|-----------------|

MessageType

Dec-Code Hex-Code MessageType Data Bytes Description
-1 0xff ERROR additional information (up to 25 bytes) message type to indicate an error
0 0x00 NONE - empty message -> no message
1 0x01 ACK_FAULT 8-bit message-type of last rec message + error code Indicates a coomunication error
2 0x02 ACK 8-bit message-type that is been acknowledged + payload ACK + payload send back (can be up to 24 bytes)
3 0x03 PONG 8-bit random value Ping Request
4 0x04 G_STATUS - Get the current system stauts code from the SMU
5 0x05 G_COM_ERROR - Get the current comunication error code from the SMU
6 0x09 G_SMU_ERROR - Get the current SMU error code from the SMU
9 0x09 RESET - Perform a soft reset of the SMU
10 0x0a FIRMWARE_V - Request the firmware-version of the SMU
11 0x0b COM_BACK_V - Request the communication backend version of the SMU
30 0x1e INIT_SENSOR 8-bit sensor-type + 8-bit sensor port Starts the initialization of a sensor at a given new port
31 0x1f S_SENS_ACTIVE 8-bit sensor no. + 8-bit status (1 or 0) Activates or deactivates a sensor
32 0x20 G_SENS_ACTIVE 8-bit sensor no. Get the activation status of an sensor
70 0x46 S_AUTO_UPDATE 8-bit status (1 or 0) Activates or deactivates the automatic sensor update
71 0x47 G_AUTO_UPDATE - Get the activation stauts of the auto update
72 0x48 MAN_UPDATE 8-bit sensor no. Performs a manual update of the given sensor
100 0x64 READ_SENSOR 8-bit sensor no. Request the sensor reading of the specified sensor

Message Flow

Requested Answer? MessageType of Answer Data Bytes of Answer Payload-Size [bytes]
NONE no - - -
ACK_FAULT no - - -
ACK no - - -
PONG yes ACK PONG + 8-bit random value from request 1 + 1 = 2
G_STATUS yes ACK G_STATUS + 16-bit status code 1 + 2 = 3
G_COM_ERROR yes ACK G_COM_ERROR + 16-bit communication error code 1 + 2 = 3
G_SMU_ERROR yes ACK G_SMU_ERROR + 16-bit SMU error code 1 + 2 = 3
RESET yes ACK RESET 1
FIRMWARE_V yes ACK FIRMWARE_V + 16-bit version 1 + 1 = 2
COM_BACK_V yes ACK COM_BACK_V + 16-bit version 1 + 1 = 2
INIT_SENSOR yes ACK INIT_SENSOR + success byte (1 or 0) + assigned 8-bit sensor no. 1 + 2 = 3
S_SENS_ACTIVE yes ACK S_SENS_ACTIVE + success byte (1 or 0) 1 + 1 = 2
G_SENS_ACTIVE yes ACK G_SENS_ACTIVE + success byte (1 or 0) + activation status byte (1 or 0) 1 + 2 = 3
S_AUTO_UPDATE yes ACK G_AUTO_UPDATE + success byte (1 or 0) 1 + 1 = 2
G_AUTO_UPDATE yes ACK S_AUTO_UPDATE + success byte (1 or 0) + activation status byte (1 or 0) 1 + 1 = 2
MAN_UPDATE yes ACK MAN_UPDATE + success byte (1 or 0) 1 + 1 = 2
READ_SENSOR yes ACK READ_SENSOR + success byte (1 or 0) + array of sensor readings up to 25

If the format of a received message is incorrect or the checksum does not match, the following must be answered:

MessageType of Answer Data Bytes of Answer Payload-Size [bytes]
ACK_FAULT received message type + communication error information up to 25

communication error information

Error Code Error Code [HEX] Error Description Data Bytes
NO_COM_ERROR 0x00 no error -
NO_START_SIGN 0x01 no start sign was found -
NO_END_SING 0x02 no end sign was found opt. rec. msg. type
INV_PAYL_SIZE 0x03 the payload-size is invalid opt. rec. msg. type + opt. rec. payload-size
INV_CHECKSUM 0x04 the checksum is invalid opt. rec. msg. type + opt. rec. checksum + opt. calc. checksum
NOT_ENOUGH_DATA 0x05 not enough data bytes received opt. rec. msg. type + opt. overall rec. number of bytes
REC_TIMEOUT 0x06 timeout during rec of data opt. rec. msg. type + opt. overall rec. number of bytes