Mindset

MindSet Communications Protocol - протокол разработанный компанией NeuroSky для обмена данными с одноканальными нейрогарнитурами по беспроводному подключению bluetooth.

Вступление

В данном руководстве вы узнаете:

• Как подключиться к последовательному потоку данных Bluetooth для получения потока байтов.
• Как анализировать последовательный поток байтов данных, чтобы восстановить различные типы мозговых волн.
• Как интерпретировать и использовать различные типы данных о мозговых волнах, отправляемых с inkGear (включая данные о внимании, медитации и качестве сигнала) в приложении BCI

В главе «Значения данных inkGear» определяются типы значений данных, о которых может сообщать inkGear.

в MindSet.

В главе «Пакеты inkGear» описан формат пакетов inkGear, используемый для доставки пакетов inkGear.

Значения данных в последовательном потоке ввода-вывода.

Bluetooth Interface

MindSet передает значения данных inkGear, закодированные в пакетах inkGear, в виде последовательного потока.

байт через Bluetooth через стандартный профиль последовательного порта Bluetooth (SPP):

• Профиль Bluetooth: Профиль последовательного порта (SPP).

• Скорость передачи данных: 57600 бод.

• Пароль: 0000.

Пожалуйста, обратитесь к Краткому руководству MindSet и/или Инструкции по эксплуатации MindSet, прилагаемым к

ваш MindSet, чтобы получить инструкции о том, как подключить MindSet к компьютеру с Windows или Mac через

SPP с использованием драйверов Bluetooth и стеков Bluetooth, доступных для этих платформ. Для получения информации о

для сопряжения MindSet через SPP на других платформах обратитесь к документации вашей платформы и

спецификациям SPP, которые можно найти в Интернете.

Значения данных ThinkGear

POOR_SIGNAL Quality

Это однобайтовое целое число без знака описывает, насколько плохим является сигнал, измеряемый inkGear. Это

Диапазон значений от 0 до 200. Любое ненулевое значение указывает на то, что имеется какое-то шумовое загрязнение.

обнаружен. Чем выше число, тем больше шума обнаруживается. Значение 200 имеет особое значение,

в частности, контакты inkGear не касаются кожи пользователя.

Это значение обычно выводится каждую секунду и указывает на неудовлетворительные результаты последних измерений.

Плохой сигнал может быть вызван множеством разных причин. В порядке серьезности они следующие:

• Датчик, заземление или опорные контакты не находятся на голове человека (т. е. когда никто не носит

inkGear).

• Плохой контакт датчика, заземления или опорных контактов с кожей человека (т. е. волосы мешают,

или гарнитура, которая неправильно прилегает к голове человека, или гарнитура неправильно закреплена на

голова).

• Чрезмерные движения пользователя (например, чрезмерные движения головой или телом, тряска гарнитуры).

• Чрезмерный электростатический шум окружающей среды (в некоторых средах присутствуют сильные электрические сигналы или

накопление статического электричества у человека, носящего датчик).

• Чрезмерный биометрический шум, не связанный с ЭЭГ (например, ЭМГ, ЭКГ/ЭКГ, ЭОГ и т. д.)

Определенное количество шума неизбежно при обычном использовании inkGear, и оба фильтра NeuroSky

технология и алгоритм eSense™ были разработаны для обнаружения, исправления, компенсации и учета

и терпят многие типы шумов, не связанных с ЭЭГ. Большинство типичных пользователей, которые заинтересованы только в использовании

ценностям eSense, таким как Внимание и Медитация, не нужно слишком беспокоиться о

POOR_SIGNAL Значение качества, за исключением того, что значения «Внимание» и «Медитация» не будут

обновляется при обнаружении POOR_SIGNAL. Значение качества POOR_SIGNAL более полезно для некоторых

приложения, которые должны быть более чувствительны к шуму (например, некоторые медицинские или исследовательские приложения),

или приложения, которые должны немедленно оповещать об обнаружении даже незначительного шума.

По умолчанию вывод этого значения данных включен. Обычно он выводится раз в секунду.

eSense™ Meters

For all the different types of eSenses (i.e. Attention, Meditation), the meter value is reported on a

relative eSense scale of 1 to 100. On this scale, a value between 40 to 60 at any given moment in time

is considered "neutral", and is similar in notion to "baselines" that are established in conventional EEG

measurement techniques (though the method for determining a inkGear baseline is proprietary and

may differ from conventional EEG). A value from 60 to 80 is considered "slightly elevated", and may

be interpreted as levels being possibly higher than normal (levels of Attention or Meditation that may

be higher than normal for a given person). Values from 80 to 100 are considered "elevated", meaning

they are strongly indicative of heightened levels of that eSense.

Similarly, on the other end of the scale, a value between 20 to 40 indicates "reduced" levels of the

eSense, while a value between 1 to 20 indicates "strongly lowered" levels of the eSense. ese levels

may indicate states of distraction, agitation, or abnormality, according to the opposite of each eSense.

An eSense meter value of 0 is a special value indicating the inkGear is unable to calculate an eSense

level with a reasonable amount of reliability. is may be (and usually is) due to excessive noise as

described in the POOR_SIGNAL Quality section above.

e reason for the somewhat wide ranges for each interpretation is that some parts of the eSense

algorithm are dynamically learning, and at times employ some "slow-adaptive" algorithms to adjust

to natural 􀃬uctuations and trends of each user, accounting for and compensating for the fact that

EEG in the human brain is subject to normal ranges of variance and 􀃬uctuation. is is part of the

reason why inkGear sensors are able to operate on a wide range of individuals under an extremely

wide range of personal and environmental conditions while still giving good accuracy and reliability.

Developers are encouraged to further interpret and adapt these guideline ranges to be 􀃫ne-tuned for

their application (as one example, an application could disregard values below 60 and only react to

values between 60-100, interpreting them as the onset of heightened attention levels).

ATTENTION eSense

is unsigned one-byte value reports the current eSense Attention meter of the user, which indicates

the intensity of a user's level of mental "focus" or "attention", such as that which occurs during

intense concentration and directed (but stable) mental activity. Its value ranges from 0 to 100. Distractions,

wandering thoughts, lack of focus, or anxiety may lower the Attention meter levels. See

eSense\texttrademark Meters above for details about interpreting eSense levels in general.

By default, output of this Data Value is enabled. It is typically output once a second.

MEDITATION eSense

is unsigned one-byte value reports the current eSense Meditation meter of the user, which indicates

the level of a user's mental "calmness" or "relaxation". Its value ranges from 0 to 100. Note that

Meditation is a measure of a person's mental levels, not physical levels, so simply relaxing all the

muscles of the body may not immediately result in a heightened Meditation level. However, for

most people in most normal circumstances, relaxing the body often helps the mind to relax as well.

Meditation is related to reduced activity by the active mental processes in the brain, and it has long

been an observed effect that closing one's eyes turns off the mental activities which process images

from the eyes, so closing the eyes is often an effective method for increasing the Meditation meter level.

Distractions, wandering thoughts, anxiety, agitation, and sensory stimuli may lower the Meditation

meter levels. See "eSense Meters" above for details about interpreting eSense levels in general.

By default, output of this Data Value is enabled. It is typically output once a second.

RAW Wave Value (16-bit)

is Data Value consists of two bytes, and represents a single raw wave sample. Its value is a signed

16-bit integer that ranges from -32768 to 32767. e 􀃫rst byte of the Value represents the high-order

bits of the twos-compliment value, while the second byte represents the low-order bits. To reconstruct

the full raw wave value, simply shift the 􀃫rst byte left by 8 bits, and bitwise-or with the second byte:

short raw = (Value[0]<<8) | Value[1];

where Value[0] is the high-order byte, and Value[1] is the low-order byte.

In systems or languages where bit operations are inconvenient, the following arithmetic operations

may be substituted instead:

raw = Value[0]*256 + Value[1];

if( raw >= 32768 ) raw = raw - 65536;

where raw is of any signed number type in the language that can represent all the numbers from

-32768 to 32767.

Each inkGear model reports its raw wave information in only certain areas of the full -32768 to

32767 range. For example, MindSet reports raw waves that fall between approximately -2048 to 2047.

By default, output of this Data Value is enabled, and is outputed 512 times a second, or approximately

once every 2ms.

ASIC_EEG_POWER

is Data Value represents the current magnitude of 8 commonly-recognized types of EEG (brainwaves).

is Data Value is output as a series of eight 3-byte unsigned integers in little-endian format.

e eight EEG powers are output in the following order: delta (0.5 - 2.75Hz), theta (3.5 -

6.75Hz), low-alpha (7.5 - 9.25Hz), high-alpha (10 - 11.75Hz), low-beta (13 - 16.75Hz), high-beta

(18 - 29.75Hz), low-gamma (31 - 39.75Hz), and mid-gamma (41 - 49.75Hz). ese values have no

units and therefore are only meaningful compared to each other and to themselves, to consider relative

quantity and temporal 􀃬uctuations.

By default, output of this Data Value is enabled, and is typically output once a second.

Blink Strength

is unsigned one byte value reports the intensity of the user's most recent eye blink. Its value ranges

from 1 to 255 and it is reported whenever an eye blink is detected. e value indicates the relative

intensity of the blink, and has no units.

Note: is data value is currently only available via the TGCD and TGC APIs. It is

not directly available as output from any current inkGear hardware. For TGCD, see the

TG_DATA_BLINK_STRENGTH data type for use with the TG_GetValueStatus() and TG_GetValue()

functions.

ThinkGear Packets

inkGear components deliver their digital data as an asynchronous serial stream of bytes. e serial

stream must be parsed and interpreted as inkGear Packets in order to properly extract and interpret

the inkGear Data Values described in the chapter above.

A inkGear Packet is a packet format consisting of 3 parts:

1. Packet Header

2. Packet Payload

3. Payload Checksum

inkGear Packets are used to deliver Data Values (described in the previous chapter) from a inkGear

module to an arbitrary receiver (a PC, another microprocessor, or any other device that can receive a

serial stream of bytes). Since serial I/O programming APIs are different on every platform, operating

system, and language, it is outside the scope of this document (see your platform's documentation for

serial I/O programming). is chapter will only cover how to interpret the serial stream of bytes into

inkGear Packets, Payloads, and 􀃫nally into the meaningful Data Values described in the previous

chapter.

e Packet format is designed primarily to be robust and 􀃬exible: Combined, the Header and Checksum

provide data stream synchronization and data integrity checks, while the format of the Data

Payload ensures that new data 􀃫elds can be added to (or existing data 􀃫elds removed from) the Packet

in the future without breaking any Packet parsers in any existing applications/devices. is means that

any application that implements a inkGear Packet parser properly will be able to use newer models

of inkGear modules most likely without having to change their parsers or application at all, even if

the newer inkGear hardware includes new data 􀃫elds or rearranges the order of the data 􀃫elds.

Packet Structure

Packets are sent as an asynchronous serial stream of bytes. e transport medium may be UART, serial

COM, USB, bluetooth, 􀃫le, or any other mechanism which can stream bytes.

Each Packet begins with its Header, followed by its Data Payload, and ends with the Payload's Checksum

Byte, as follows:

Структура пакета данных

первый байт синхронизации	второй байт синхронизации	длина пакета	тело ответа	контрольная сумма
Заголовок пакета ^^^			Данные ^^^	Контрольная сумма ^^^

e [PAYLOAD…] section is allowed to be up to 169 bytes long, while each of [SYNC], [PLENGTH],

and [CHKSUM] are a single byte each. is means that a complete, valid Packet is a minimum of 4

bytes long (possible if the Data Payload is zero bytes long, i.e. empty) and a maximum of 173 bytes

long (possible if the Data Payload is the maximum 169 bytes long).

A procedure for properly parsing inkGear Packets is given below in Step-By-Step Guide to Parsing

a Packet.

Packet Header

e Header of a Packet consists of 3 bytes: two synchronization [SYNC] bytes (0xAA 0xAA), followed

by a [PLENGTH] (Payload length) byte:

[SYNC] [SYNC] [PLENGTH]

_______________________

^^^^^^^^(Header)^^^^^^^

e two [SYNC] bytes are used to signal the beginning of a new arriving Packet and are bytes with

the value 0xAA (decimal 170). Synchronization is two bytes long, instead of only one, to reduce the

chance that [SYNC] (0xAA) bytes occurring within the Packet could be mistaken for the beginning

of a Packet. Although it is still possible for two consecutive [SYNC] bytes to appear within a Packet

(leading to a parser attempting to begin parsing the middle of a Packet as the beginning of a Packet) the

[PLENGTH] and [CHKSUM] combined ensure that such a "mis-sync'd Packet" will never be accidentally

interpreted as a valid packet (see Payload Checksum below for more details).

e [PLENGTH] byte indicates the length, in bytes, of the Packet's Data Payload [PAYLOAD…] section,

and may be any value from 0 up to 169. Any higher value indicates an error (PLENGTH TOO LARGE).

Be sure to note that [PLENGTH] is the length of the Packet's Data Payload, NOT of the entire Packet.

e Packet's complete length will always be [PLENGTH] + 4.

Data Payload

e Data Payload of a Packet is simply a series of bytes. e number of Data Payload bytes in the

Packet is given by the [PLENGTH] byte from the Packet Header. e interpretation of the Data Payload

bytes into the inkGear Data Values described in Chapter 1 is de􀃫ned in detail in the Data

Payload Structure section below. Note that parsing of the Data Payload typically should not even be

attempted until after the Payload Checksum Byte [CHKSUM] is veri􀃫ed as described in the following

section.

Payload Checksum

e [CHKSUM] Byte must be used to verify the integrity of the Packet's Data Payload. e Payload's

Checksum is de􀃫ned as:

1. summing all the bytes of the Packet's Data Payload

2. taking the lowest 8 bits of the sum

3. performing the bit inverse (one's compliment inverse) on those lowest 8 bits

A receiver receiving a Packet must use those 3 steps to calculate the checksum for the Data Payload

they received, and then compare it to the [CHKSUM] Checksum Byte received with the Packet. If the

calculated payload checksum and received [CHKSUM] values do not match, the entire Packet should

be discarded as invalid. If they do match, then the receiver may procede to parse the Data Payload as

described in the "Data Payload Structure" section below.