BMD101 Product Brief (Preliminary) 2012

NeuroSky BMD101 Product Brief Rev 0.9.2

NeuroSky Confidential

Page 11

[CODE] Definitions Table

Extended

Code Level

[CODE]

(Byte)

[LENGTH]

Data Value Meaning

0

0x02

N/A

Signal Quality (0—sensor off, 200—sensor on)

0

0x03

N/A

Real-time Heart Rate (Beats Per Minute)

0

0x08

N/A

Don’t Care

0

0x80

2

16-bit Raw Data (2’s Complement)

0

0x84

5

Don’t Care

0

0x85

3

Don’t Care

Step-By-Step Guide to Parsing a Packet

1. Keep reading bytes from the stream until a [SYNC] byte (0xAA) is encountered.

2. Read the next byte and ensure it is also a [SYNC] byte (if not, return to step 1.)

3. Read the [PLENGTH] byte.

4. Read the next PLENGTH bytes of the [PAYLOAD...], saving them into a storage area (such as an

unsigned char payload [256] array). Sum up each byte as it is read by incrementing a checksum

accumulator.

5. Take the lowest 8 bits of the checksum accumulator and invert them. Here is the C code:

checksum &= 0xFF;

checksum = ~checksum & 0xFF;

6. Read the [CRC] byte and verify that it matches your calculated checksum (if not, return to step 1).

7. Loop until all bytes (and hence, DataRows) have been parsed from the data payload[] array:

a) Parse and count the number of [EXCODE] bytes (0x55) that may be at the beginning of the

current DataRow.

b) Parse the [CODE] byte for the current DataRow.

c) If applicable, parse the [LENGTH] byte for the current DataRow.

d) Parse and handle the [DATA...] byte(s) of the current DataRow, based on the DataRow's

[EXCODE] level, [CODE], and [LENGTH].

e) If not all bytes have been parsed from the payload[] array, return to 7a. to parse the next

DataRow.