Databank service

Static packet pool. Maintains a fixed array of SPP_Packet_t objects and a free-list stack. Producers call SPP_SERVICES_DATABANK_getPacket() to lease a packet, fill it with SPP_SERVICES_DATABANK_packetData(), and publish it. After all pub/sub subscribers have processed it, SPP_SERVICES_PUBSUB_publish() automatically returns it to the pool. malloc is never called.

Pool size is controlled by K_SPP_DATABANK_SIZE (default 5, configurable via CMake).

Note

For the conceptual explanation of what the databank is and why it exists, see Databank. This page is the API reference for the service itself.

---

Files

File	Description
databank.h	Public API
databank.c	Implementation

---

API

SPP_RetVal_t   SPP_SERVICES_DATABANK_init(void);
SPP_Packet_t  *SPP_SERVICES_DATABANK_getPacket(void);
SPP_RetVal_t   SPP_SERVICES_DATABANK_returnPacket(SPP_Packet_t *p_packet);
SPP_RetVal_t   SPP_SERVICES_DATABANK_packetData(SPP_Packet_t *p_packet,
                                        spp_uint16_t apid,
                                        spp_uint16_t seq,
                                        const void  *p_data,
                                        spp_uint16_t dataLen);
spp_uint32_t   SPP_SERVICES_DATABANK_freeCount(void);

---

SPP_SERVICES_DATABANK_packetData()

Fills all packet fields in one call: - Zeroes the full packet struct (ensures deterministic CRC over padding bytes) - Sets primaryHeader: version, apid, seq, payloadLen - Sets secondaryHeader.timestampMs from SPP_HAL_TIME_getTimeMs() - Copies dataLen bytes from p_data into payload - Computes CRC-16/CCITT over the full packet minus the CRC field and stores it in p_packet->crc

---

Usage

// Producer (inside a ServiceTask)
SPP_Packet_t *p_pkt = SPP_SERVICES_DATABANK_getPacket();
if (p_pkt == NULL)
{
    SPP_LOGW("MY_SVC", "pool empty, dropping reading");
    return;
}

float data[3] = { altitude, pressure, temperature };
(void)SPP_SERVICES_DATABANK_packetData(p_pkt, K_MY_APID, s_seq++,
                               data, (spp_uint16_t)sizeof(data));
(void)SPP_SERVICES_PUBSUB_publish(p_pkt);
// p_pkt is returned to the pool automatically by SPP_SERVICES_PUBSUB_publish()

---

Rules

• Never call returnPacket twice on the same pointer — the double-return guard will return K_SPP_ERROR_ALREADY_INITIALIZED.
• Never use a packet after calling publish() or returnPacket() — the memory may be reused immediately.
• If getPacket returns NULL, the pool is exhausted. Either increase K_SPP_DATABANK_SIZE or ensure subscribers complete quickly.
• init is idempotent — calling it twice returns K_SPP_ERROR_ALREADY_INITIALIZED and is harmless.