protocol/com.neurotec.brainaccess.protocol/TimeSyncBlock

TimeSyncBlock

Wire protocol v1 of the time-sync characteristic (GattUuids.TIME_SYNC_CHARACTERISTIC, firmware 3.8.0+), shared with the device firmware. The device builds the 20-byte value inside its read handler from its own clock and the sample it numbered last, so one timed read ties the host's clock, the device's clock and the ADS1299 sample counter together (see TimeSync in :core). Little-endian:

off	type	field	meaning
0	u8	version	1; any other value is not understood
1	u8	flags	FLAG_STREAMING, FLAG_IMPEDANCE, FLAG_SAMPLE_VALID; other bits ignored
2	u8	stream_gen	low 8 bits of the stream generation of the anchored sample
3	u8	seq	incremented on every read the device answers
4	u32	sample_number	sample numbered last, as the packet footers count; 0 without SAMPLE_VALID
8	u32	sample_age_us	device time since that sample's DRDY; SAMPLE_AGE_INVALID without SAMPLE_VALID, SAMPLE_AGE_MAX saturated
12	u32	t_now_us	low 32 bits of the device's microsecond clock, taken first in the read handler
16	u16	conn_interval	the link's connection interval, 1.25 ms units
18	u16	reserved	0

Properties

FLAG_IMPEDANCE

const val FLAG_IMPEDANCE: Int

Impedance mode: the sample counter is not uniform in time (it jumps a sweep at a time).

FLAG_SAMPLE_VALID

const val FLAG_SAMPLE_VALID: Int

A sample has been numbered since the stream started.

FLAG_STREAMING

const val FLAG_STREAMING: Int

The ADS1299 is converting.

OFFSET_CONN_INTERVAL

const val OFFSET_CONN_INTERVAL: Int = 16

OFFSET_FLAGS

const val OFFSET_FLAGS: Int = 1

OFFSET_SAMPLE_AGE_US

const val OFFSET_SAMPLE_AGE_US: Int = 8

OFFSET_SAMPLE_NUMBER

const val OFFSET_SAMPLE_NUMBER: Int = 4

OFFSET_SEQ

const val OFFSET_SEQ: Int = 3

OFFSET_STREAM_GEN

const val OFFSET_STREAM_GEN: Int = 2

OFFSET_T_NOW_US

const val OFFSET_T_NOW_US: Int = 12

OFFSET_VERSION

const val OFFSET_VERSION: Int = 0

PROTOCOL_VERSION

const val PROTOCOL_VERSION: Int = 1

REPLY_SIZE

const val REPLY_SIZE: Int = 20

SAMPLE_AGE_INVALID

const val SAMPLE_AGE_INVALID: Long = 4294967295

sample_age_us without FLAG_SAMPLE_VALID.

SAMPLE_AGE_MAX

const val SAMPLE_AGE_MAX: Long = 4294967294

sample_age_us saturated: this or more, so not a usable point.

Functions

parse

fun parse(value: ByteArray): TimeSyncReply?

The reply's fields, or null when value is not a v1 reply: shorter than REPLY_SIZE — an empty read is what both firmware without the characteristic and a failed read return — or of another version. A longer value is read as v1, for whatever a later version appends.