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The FloripaSat Protocol (FSP) was developed with the purpose of standardizing the communication between the FloripaSat's modules (EPS, OBDH and TT&C). This protocol does not specify the physical layer, so it can be used, for instance, over SPI, I²C or UART.
The packet's fields defined by the FSP (FloripaSat Protocol) are shown below:
| Field | Description | Length (Bytes) |
|---|---|---|
| SOD | Start of data (always 0x7E) | 1 |
| SRC | Source address | 1 |
| DST | Destination address | 1 |
| Length | Length of the packet payload | 1 |
| Type | Type of packet | 1 |
| Payload | Data of the packet | n* |
| CRC | CRC-16-CCITT bytes | 2 |
*The n value is defined by the field "Length" and can assume values between 0 and 248. Therefore, the packet's total size can reach from 7 to 255 bytes.
By team definition the module's address are:
| Module | Address |
|---|---|
| EPS | 1 |
| TTC | 2 |
| OBDH | 3 |
| Packet Type | Value |
|---|---|
| Data without ACK | 1 |
| Data with ACK | 2 |
| Command without ACK | 3 |
| Command with ACK | 4 |
| ACK | 5 |
| NACK | 6 |
The table below shows the current possible commands:
| Command | Value |
|---|---|
| NOP | 1 |
| Send Data | 2 |
| Request RF Mutex | 3 |
| Shutdown | 4 |
In way to grant the correctness of the transmitted data, a Cyclic Redundancy Check is made. The standard used is CRC-16-CCITT (initial value = 0 and polynomial = 0x1021). All the FSP's packet fields, except the SOD, are used to generate the CRC value.
There is an usage example code available here.
All source code of the project can be found in GitHub.
The official website of the project is www.floripasat.ufsc.br.