Polaris Client Library

The Polaris client library provides remote access to the receiver using functions that wrap CSP protocol messages.

Frame Store

Each received AIS message is tagged with a 32-bit sequence number and stored in NOR-flash with reception metadata (estimated center frequency offset, signal level) and a 64-bit timestamp (number of nanoseconds since midnight on January 1st, 1970).

All 1-5 slot messages are stored in the same store, and consumes 256 bytes of NOR flash, including metadata, independent on the number of slots in the message. The store is a ring buffer and wraps around every 261120 messages.

Frames can be selectively downloaded by their sequence number through the store CSP service, and provides access to the full AIS messages and metadata.

If an external store is preferred, the mirror mode can be used to forward all received frames to another CSP node. Refer to sl_polaris_store_mirror() for this functionality.

Both the normal frame request and mirror frames pass received frames to a callback function matching sl_polaris_frame_cb_t() prototype.

The example below shows a simple frame callback function that just prints the length and first byte of received frames, and a request_frames() function that requests the last 8 frames from the CSP node on address 20. Error handling has been left out for brevity.

static int frameprint_cb(sl_polaris_store_frame_t *frame, void *arg)
{
    printf("Got a %u byte frame and the first byte is %02hhx\n",
           frame->length, frame->data[0]);
return 0;
}

void request_frames(void)
{
// Prepare bitmap for 8 frames
     uint8_t bitmap[SL_POLARIS_STORE_BITMAP_SIZE] = {0xff};
// Request from CSP node 20, call callback for each frame
sl_polaris_store_read(20, 1000, 0, bitmap, frameprint_cb, NULL);
}

Typedefs

typedef int (*sl_polaris_frame_cb_t)(sl_polaris_store_frame_t *frame, void *arg)

Frame callback function prototype.

Callback function prototype used by store mirror and read functions.

Param frame:: Pointer to structure with frame data. The structure data has been converted to host byte order.
Param arg:: Arbitrary data pointer passed from the mirror/read function call. Can be used to pass any additional data required by the callback function.
Return:: 0 to continue iteration over received frames, or a non-zero value to abort the iteration.

Functions

int sl_polaris_store_mirror(uint8_t node, uint32_t timeout, uint8_t dest_node, uint8_t dest_port, uint32_t time_ms)

Request store frame mirroring.

This function requests the Polaris to mirror received frames to another CSP system.

The time_ms specifies the amount of time the system should keep sending frames. This ensures that the receiver will eventually stop sending frames if the mirror client no longer waits for frames. A client can extend the mirror period by sending a new mirror request before the timeout expires.

Parameters:

node – CSP address of the Polaris node.
timeout – Timeout of the command in milliseconds.
dest_node – Destination CSP address.
dest_port – Destination CSP port.
time_ms – Milliseconds the system should mirror frames for.

Returns:

0 on success, and a negative error code on error.

int sl_polaris_store_mirror_recv(uint8_t node, uint8_t port, uint32_t timeout, sl_polaris_frame_cb_t cb, void *arg)

Receive mirror frames from device.

This function requests frame mirroring and calls the cb function for each received frame. It automatically refreshes the mirror timeout every 60 seconds.

Parameters:

node – CSP address of the Polaris node.
port – Mirror frame receive port.
timeout – Timeout of the command in milliseconds.
cb – Frame callback function.
arg – Pointer argument passed to callback function.

Returns:

0 on success, and a negative error code on error.

int sl_polaris_store_read(uint8_t node, uint32_t timeout, uint32_t start, uint8_t *bitmap, sl_polaris_frame_cb_t cb, void *arg)

Request AIS frames from store.

This function requests a number of received AIS frames from the store. Frames are selected using a starting sequence number and a bitmap. The last sequence number to be received can be read using the store.seq property or start=0 can be used to request the most recent frames.

Frames are requested backwards from start, i.e. the start fields selects the maximum sequence number to request.

The bitmap field is used to request selected messages backwards from the start sequence number. If bit n is set, the receiver will send the message with sequence number start - n, i.e. bit 0 must be set to request the message with sequence number start. Bit 0 is the bit immediately after the start field and bit 255 is the last bit in the packet.

E.g. to request messages with sequence number 10, 9, 8, 7, 2 and 1 set:

start = 10, bitmap = [0xf0, 0xc0, 0x00, 0x00, …, 0x00]

The bitmap argument must be SL_POLARIS_STORE_BITMAP_SIZE bytes (currently 32, allowing up to 256 frames per request).

Parameters:

node – CSP address of the Polaris node.
timeout – Timeout of the command in milliseconds.
start – Start frame request number. Use 0 to request from most recent frame.
bitmap – Bitmap of frames from start to request.
cb – Frame callback function.
arg – Pointer argument passed to callback function.

Returns:

0 on success, and a negative error code on error.

Sample Buffer

This file provides functions used to read raw or store sample data from the Polaris sample buffer via CSP.

The source can be either short (fixed length) bursts of full spectrum data or variable length samples from one of the 4 AIS channels.

The number of captured samples must be 8192 for SL_POLARIS_SAMPLEBUF_SOURCE_RAW source.

Samples are 32-bit words consisting of 16-bit IQ channels.

Note

The sample commands write data into external SDRAM, which is automatically enabled and kept powered on after sampling. This results in a higher power consumption after the first sample request is received.

Functions

int sl_polaris_sample_read(uint8_t node, uint32_t timeout, uint8_t source, uint32_t *out, size_t outlen)

Read data from sample buffer.

The Polaris device will send the samples via CSP to the requesting node address immediately after request.

Parameters:

node – CSP address of the Polaris node.
timeout – Timeout of the command in milliseconds.
source – Sample source identifier. Must be one of: SL_POLARIS_SAMPLEBUF_SOURCE_RAW SL_POLARIS_SAMPLEBUF_SOURCE_CH1 SL_POLARIS_SAMPLEBUF_SOURCE_CH2 SL_POLARIS_SAMPLEBUF_SOURCE_CH3 SL_POLARIS_SAMPLEBUF_SOURCE_CH4
out – Pointer to output data array.
outlen – Size of the output array in bytes (must be 4x number of samples).

Returns:

0 on success, and a negative error code on error.

int sl_polaris_sample_store(uint8_t node, uint32_t timeout, uint8_t source, uint8_t dest, size_t samples, uint32_t id)

Save sample buffer data.

This function is used to store raw sample data on the Polaris device for later download using BTP.

Parameters:

node – CSP address of the Polaris node.
timeout – Timeout of the command in milliseconds.
source – Sample source identifier. Must be one of: SL_POLARIS_SAMPLEBUF_SOURCE_RAW SL_POLARIS_SAMPLEBUF_SOURCE_CH1 SL_POLARIS_SAMPLEBUF_SOURCE_CH2 SL_POLARIS_SAMPLEBUF_SOURCE_CH3 SL_POLARIS_SAMPLEBUF_SOURCE_CH4
dest – Destination identifier. Must be one of: SL_POLARIS_SAMPLEBUF_DEST_CSP SL_POLARIS_SAMPLEBUF_DEST_MEM SL_POLARIS_SAMPLEBUF_DEST_SDCARD
samples – Number of samples to store.
id – Identification number of sample. Samples stored to the SD-card will be named s<id>.bin, e.g. s1000.bin for sample ID 1000.

Returns:

0 on success, and a negative error code on error.

Remote Command

This file provides functions for running debug shell commands remotely.

It is meant as a debugging aid and should not be required during normal operation of the device.

Functions

int sl_polaris_shell_run(uint8_t node, uint32_t timeout, const char *cmd)

Run debug shell command.

This function allows debug shell commands to be run on the Polaris system. The command is evaluated on the remote systems, and the command return value is returned. Output from the command is not available.

Parameters:

node – CSP address of the property node.
timeout – Timeout of the command in milliseconds.
cmd – Command to execute

Returns:

0 on success, and a negative error code on error.

Protocol Specification

This file specifies the available CSP services and ports on the Polaris receiver.

It should not be necessary for clients to use these definitions directly. Instead, use the wrapper functions from this library which handles the protocol and performs necessary byte order conversion.

Defines

SL_POLARIS_DEFAULT_ADDRESS: Default CSP address.

SL_POLARIS_PORT_SAMPLEBUF: CSP ports.

SL_POLARIS_PORT_STORE

SL_POLARIS_PORT_BOOTLOADER

SL_POLARIS_PORT_SHELL

SL_POLARIS_PORT_BOOTLOADER2

SL_POLARIS_PORT_STORE_MIRROR_RECV: Default mirror frame receive port.

SL_POLARIS_ERR_NONE: Error codes.

SL_POLARIS_ERR_INVAL

SL_POLARIS_ERR_IO

SL_POLARIS_ERR_NOMEM

SL_POLARIS_ERR_BUSY

SL_POLARIS_SAMPLEBUF_READ_REQ

SL_POLARIS_SAMPLEBUF_READ_REP

SL_POLARIS_SAMPLEBUF_READ_CHUNK

SL_POLARIS_SAMPLEBUF_FREE

SL_POLARIS_SAMPLEBUF_SOURCE_RAW

SL_POLARIS_SAMPLEBUF_SOURCE_CH1

SL_POLARIS_SAMPLEBUF_SOURCE_CH2

SL_POLARIS_SAMPLEBUF_SOURCE_CH3

SL_POLARIS_SAMPLEBUF_SOURCE_CH4

SL_POLARIS_SAMPLEBUF_SOURCE_AIS1_CH87B

SL_POLARIS_SAMPLEBUF_SOURCE_AIS2_CH88B

SL_POLARIS_SAMPLEBUF_SOURCE_AIS3_CH75

SL_POLARIS_SAMPLEBUF_SOURCE_AIS4_CH76

SL_POLARIS_SAMPLEBUF_DEST_CSP

SL_POLARIS_SAMPLEBUF_DEST_MEM

SL_POLARIS_SAMPLEBUF_DEST_SDCARD

SL_POLARIS_SAMPLEBUF_FL_FORCE_INTRAM

SL_POLARIS_SAMPLEBUF_FL_SYNC_PPS

SL_POLARIS_SAMPLEBUF_READ_CHUNK_SAMPLES

SL_POLARIS_STORE_FRAME

SL_POLARIS_STORE_MIRROR_REQ

SL_POLARIS_STORE_MIRROR_REP

SL_POLARIS_STORE_READ_REQ

SL_POLARIS_STORE_READ_REP

SL_POLARIS_STORE_FRAME2

SL_POLARIS_STORE_CHANNEL_MASK

SL_POLARIS_STORE_FLAGS_MASK

SL_POLARIS_STORE_FLAGS_OFFSET

SL_POLARIS_STORE_MAX_DATALEN

SL_POLARIS_STORE_FRAME_OVERHEAD

SL_POLARIS_STORE_BITMAP_SIZE

SL_POLARIS_SHELL_RUN_REQ

SL_POLARIS_SHELL_RUN_REP

SL_POLARIS_SHELL_RUN_KEY

SL_POLARIS_SHELL_RUN_MAX

struct sl_polaris_req_t

Public Members

uint8_t type

struct sl_polaris_rep_t

Public Members

uint8_t type

uint8_t error

struct sl_polaris_samplebuf_read_req_t

Public Members

uint8_t type

uint8_t source

uint8_t dest

uint8_t flags

uint32_t id

uint32_t samples

struct sl_polaris_samplebuf_read_rep_t

Public Members

uint8_t type

uint8_t error

uint32_t id

uint32_t addr

struct sl_polaris_samplebuf_read_chunk_t

Public Members

uint8_t type

uint8_t error

uint16_t seq

uint16_t total

uint32_t data[32]

struct sl_polaris_samplebuf_free_req_t

Public Members

uint8_t type

uint8_t flags

uint32_t addr

struct sl_polaris_samplebuf_free_rep_t

Public Members

uint8_t type

uint8_t error

struct sl_polaris_store_frame_t

Public Members

uint8_t type: Must be SL_POLARIS_STORE_FRAME2.

uint8_t error: Error code.

uint32_t seq: Sequence number of this frame.

uint64_t time: Time of reception (nanoseconds since 1/1/1970).

uint8_t channel_and_flags

AIS channel this message was received on and pps flags.

bit 0-1: channel from 0 to 3 bit 2-4: reserved bit 5: pps synchronized samples bit 6: pps time set bit 7: pps valid

int16_t power_deci_dbm: Signal power in 1/10 dBm.

int16_t frequency_hz: Estimated frequency offset.

uint8_t length: Number of bytes in data field.

uint8_t data[160]: Raw AIS message, excludes flag bytes, includes FCS.

struct sl_polaris_store_mirror_req_t

Public Members

uint8_t type

uint8_t dest_node

uint8_t dest_port

uint32_t timeout_ms

struct sl_polaris_store_mirror_rep_t

Public Members

uint8_t type

uint8_t error

struct sl_polaris_store_read_req_t

Public Members

uint8_t type

uint32_t start

uint8_t bitmap[32]

struct sl_polaris_store_read_rep_t

Public Members

uint8_t type

uint8_t error

struct sl_polaris_shell_run_req_t

Public Members

uint8_t type: Must be SL_POLARIS_SHELL_RUN_REQ.

uint8_t flags: Flags, currently unused - set to zero.

uint32_t key: Must be SL_POLARIS_SHELL_RUN_KEY.

uint8_t cmd[100]: Command to execute.

struct sl_polaris_shell_run_rep_t

Public Members

uint8_t type: Must be SL_POLARIS_SHELL_RUN_REP.

uint8_t error: Error code.