Skald, who advertises to the world

Skald, a minimalistic BLE advertising stack.

About

Skald is a very minimalistic BLE implementation, implementing the broadcaster role only. With this focus, the stack allows for setting up different kind of beacons using an extremely low memory footprint.

Design Decisions and Limitations

  • support for local addresses only (using luid to generate them)
  • advertising interval is configured during compile time, override by setting CFLAGS+=-DSKALD_INTERVAL=xxx
  • advertising channels are configured during compile time, override by setting CFLAGS+=-DSKALD_ADV_CHAN={37,39}

Implementation state

Supported:

  • advertising of custom GAP payloads
  • iBeacon (full support)
  • Eddystone (partly supported)

Limitations:

  • currently Skald supports random static addresses only (generated using the luid module)

void skald_init(void)

Initialize Skald and the underlying radio.

void skald_adv_start(skald_ctx_t * ctx)

Start advertising the given packet.

The packet will be send out each advertising interval (see SKALD_INTERVAL) on each of the defined advertising channels (see SKALD_ADV_CHAN).

Parameters

ctx:start advertising this context

void skald_adv_stop(skald_ctx_t * ctx)

Stop the ongoing advertisement.

Parameters

ctx:stop advertising this context

void skald_generate_random_addr(uint8_t * buf)

Generate a random public address.

Note

buf must be able to hold BLE_ADDR_LEN (6) bytes

Parameters

buf:the generated address is written to this buffer

SKALD_INTERVAL

Static advertising interval. 

1
(1 * US_PER_SEC)
SKALD_ADV_CHAN

Static list of used advertising channels. 

1
{ 37, 38, 39 }
struct skald_uuid_t

UUID representation format used by Skald.

uint8_t u8()

UUID with byte-wise access.

struct skald_ctx_t

Advertising context holding the advertising data and state.

netdev_ble_pkt_t pkt

packet holding the advertisement (GAP) data

xtimer.h::xtimer_t timer

timer for scheduling advertising events

uint32_t last

last timer trigger (for offset compensation)

uint8_t cur_chan

keep track of advertising channels