Datasheet

FIFO Data Contains 3 Bytes per Channel
The FIFO data is left-justified, meaning that the MSB is always in the same location regardless of the ADC resolution
setting. FIFO DATA[18] – [23] are not used. Table 2 shows the structure of each triplet of bytes (containing the 18-bit
ADC data output of each channel).
Each data sample in SpO
2
mode comprises two data triplets (3 bytes each), To read one sample, requires an I
2
C read
command for each byte. Thus, to read one sample in SpO
2
mode, requires 6 I
2
C byte reads. The FIFO read pointer is
automatically incremented after the first byte of each sample is read.
Write/Read Pointers
Write/Read pointers are used to control the flow of data in the FIFO. The write pointer increments every time a new
sample is added to the FIFO. The read pointer is incremented every time a sample is read from the FIFO. To reread a
sample from the FIFO, decrement its value by one and read the data register again.
The FIFO write/read pointers should be cleared (back to 0x00) upon entering SpO
2
mode or HR mode, so that there is
no old data represented in the FIFO. The pointers are automatically cleared if V
DD
is power-cycled or V
DD
drops below
its UVLO voltage.
Figure 2. Graphical Representation of the FIFO Data Register. It shows IR and Red in SpO
2
Mode.
BYTE 1
FIFO_
DATA[17]
FIFO_
DATA[16]
BYTE 2
FIFO_
DATA[15]
FIFO_
DATA[14]
FIFO_
DATA[13]
FIFO_
DATA[12]
FIFO_
DATA[11]
FIFO_
DATA[10]
FIFO_
DATA[9]
FIFO_
DATA[8]
BYTE 3
FIFO_
DATA[7]
FIFO_
DATA[6]
FIFO_
DATA[5]
FIFO_
DATA[4]
FIFO_
DATA[3]
FIFO_
DATA[2]
FIFO_
DATA[1]
FIFO_
DATA[0]
Sample 2: RED Channel
(Byte 1-3)
Sample 2: IR Channel
(Byte 1-3)
NEWER
SAMPLES
2(a)
Sample 1: IR Channel
(Byte 1-3)
Sample 1: RED Channel
(Byte 1-3)
OLDER SAMPLES
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Maxim Integrated │ 15
MAX30102 High-Sensitivity Pulse Oximeter and
Heart-Rate Sensor for Wearable Health