Renesas OB1203SD-BT-EVK Evaluation Kit Manual

OB1203SD

Integrated Context Engine for Heart Rate and Bl ood Oxygen Saturation measurement with BLE

X0008647 Rev.1.2
Feb.8.21

Page 1

Copyright © 2021

TLSR8258

-BT-EVK

The Integrated Context Engine (ICE) for Biosensing
(see Figure 2) includes:

■

Renesas OB1203 reflective photoplethysmography
(PPG), proximity (PS) and light / color (LS/CS)
sensor

■

Telink’s TLSR8258F512 micro controller with
Bluetooth Low Energy (BLE) radio

■

LiPo’s LP201030 rechargeable Li ion battery , 3.7
V, 40mAh, 10

[1] Light and color sensing function not used in this application.

× 30 × 2 mm

3

.

The ICE hardware performs reflective, non-invasive
measurements (e.g., at the fingertip), transmits the data
via BLE to a smartphone or tablet (see Figure 1), where
the Heart Rate (HR) and blood oxygen saturation
(SpO

) are determined by an Android app. During this

2

process the proximity sensor function keeps the
measurement running as long as there is a finger
present.

Controller

Figure 1. Block Diagram of ICE

OB1203 Sensor Features

■

Highly reliable and industry-proven OSIP package
with integrated cover glass for hypoallergenic
products

■

Integrated and factory trimmed LED source, driver,
and photodetector

■

PPG (Heart Rate and Blood Oxygen Concentration):

●

Aesthetic industrial design options with unique
far-red LED allowing SpO
behind visibly dark, IR-transmissive ink.

●

16 to 18 bits output resolution

●

High speed sampling up to 3200 samples per
second for highest resolution and improved
SNR

●

On-chip averaging and FIFO data storage
enable convenient asynchronous access to data

measurements

2

[1]

Evaluation Kit Manual

■

Proximity Sensor:

●

Up to 16 bits resolution

●

Ambient light suppression

●

Analog and digital crosstalk cancelation

■

Wide operation temperature range: -40°C to +85°C

■

Wide supply voltage range:

●

1.7V to 3.6V for digital / analog

●

3.3 V to 5.0 V for LEDs

■

I2C interface capable of 100kHz or 400kHz
communication

■

Programmable level-based interrupt functions

■

Industry’s smallest package: 4.2 × 2 × 1.2 mm3
14-pin module

Radio Mode Features

■

Telink TLSR8258F512

●

BT 4.2 BLE 2.4GHz radio

●

32-bit MCU at 48MHz, 512 kB flash, 32kB SRAM

●

Wide supply voltage range: 1.9V to 3.6V

■

Compact size: 32-pin, 5.0 × 5.0 × 0.75 mm package

ICE Characteristics

■

PCB (see Figure 2):

●

Operation temperature range: -40°C to +85°C

●

PCB supply voltage range: 3.3 V to 6.5V

●

PCB: 40mm × 11mm (21mm with program pads) ×
5mm with USB charge connector (3.1mm without)

●

Program pad PCB section removable

■

Battery life:

●

150 × 30s measurements

●

Typical PCB quiescence current: 0.5 µA at 4V

●

Battery capacity: 40mAh if charged up to 4.2V

●

Battery operation: 3.3V to 4.2V

●

Rechargeable via USB Micro cable

●

> 70% shelf: 1 year stored (-20°C to 30°C)

■

Battery operating temperature range -20C° to + 60°C

Applications

■

Mobile devices: Wearables, Fitness, and Accessories

■

Industrial: Worker Safety, Driver Assist

OB1203SD-BT-EVK Evaluation Kit Manual

X0008647 Rev.1.2
Feb.8.21

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Contents

1. ICE Hardware.................................................................................................................................................. 3

2. Sensor Function............................................................................................................................................. 4

3. Getting Started ............................................................................................................................................... 5

4. Resources ....................................................................................................................................................... 7

4.1 PCB Schematics .................................................................................................................................... 7

4.2 PCB Layout ............................................................................................................................................ 9

4.3 PCB Components ................................................................................................................................ 10

4.4 Programming Pins ............................................................................................................................... 10

4.5 Programming Tools ............................................................................................................................. 10

4.6 Bill of Materials .................................................................................................................................... 11

4.7 OB1203 Run Mode .............................................................................................................................. 11

4.8 HR Algorithm ....................................................................................................................................... 12

4.9 SpO2 Algorithm .................................................................................................................................... 12

4.10 Recharging the Battery ........................................................................................................................ 12

4.11 Troubleshoot ........................................................................................................................................ 12

5. Ordering Information ................................................................................................................................... 13

6. Revision History .......................................................................................................................................... 13

Figures

Figure 1. Block Diagram of ICE ................................................................................................................................ 1

Figure 2. ICE Hardware ............................................................................................................................................ 3

Figure 3. Reflective HR and SpO2 Measurement .................................................................................................... 4

Figure 4. PPG Signal Measured at Finger Tip .......................................................................................................... 4

Figure 5. Recommended Height of a Finger Rest .................................................................................................... 4

Figure 6. PCB Activation Switch ............................................................................................................................... 5

Figure 7. Finger Rest Examples ............................................................................................................................... 6

Figure 8. Components for the OB1203 Sensor ........................................................................................................ 7

Figure 9. OB1203 Schematics .................................................................................................................................. 7

Figure 10. MCU Schematics ..................................................................................................................................... 8

Figure 11. Power Schematics ................................................................................................................................... 8

Figure 12. Connector Schematics ............................................................................................................................ 9

Figure 13. PCB Bottom with Telink Chip Left of the Middle ..................................................................................... 9

Figure 14. PCB Top with OB1203 at the Right ......................................................................................................... 9

Figure 15. PCB Functions ....................................................................................................................................... 10

Figure 16. Functions of Programming Pins ............................................................................................................ 10

Tables

Table 1. Bill of Materials ......................................................................................................................................... 11

OB1203SD-BT-EVK Evaluation Kit Manual

X0008647 Rev.1.2
Feb.8.21

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1. ICE Hardware

Figure 2. ICE Hardware

OB1203SD-BT-EVK Evaluation Kit Manual

X0008647 Rev.1.2
Feb.8.21

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2. Sensor Function

Figure 3 shows the principal of a reflective measu rement. In this case the sensor is located under a cover glass
that uses black and IR transmissive ink to visibly hide the PCB / sensor module. Light from the sensor module’ s
LED is reflected from the finger tissue and detected by the photo diode. As blood absorbs light, changes in bl ood
volume (caused by the heart beat) generate a small change in the intensity of the reflected light.

Figure 3. Reflective HR and SpO2 Measurement

Figure 4 shows this signal change of about 3,000 counts (peak to peak) on top of a DC signal of 190,000 counts
due to direct reflections from the finger tissue.

Figure 4. PPG Signal Measured at Finger Tip

The DC content of the signal as well as light reflections in the sensor set up (like reflections from the cover glass,
etc.) are called optical crosstalk. For a high AC t o DC ratio, a good AC signal and / or a small DC signal are key.

■

In order to get a good blood flow / good AC signal, the finger pressure onto the sensor needs to be light.

■

In order to keep the optical cross talk small, the dist ance from the sensor to the finger should be kept to a
minimum.

For example, without using a cover glass the f inger pressure can be kept low by using a finger rest (like the
cover of the provided sensor house) to spread the finger – sensor force over a larger area.

To recycle some of the diffused light the best col or f or the finger rest is white. To avoid additional optical cros s
talk the finger rest should not be thicker than the package (see Figure 5).

Figure 5. Recommended Height of a Finger Rest

OB1203SD-BT-EVK Evaluation Kit Manual

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Feb.8.21

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3. Getting Started

1. Install the Android app:
a. Download the app from the USB stick or GitHub

(

https://github.com/hyperdga/Android_OB1203_serial_BLE)

b. Click on the app to install.
c. Go to Settings -> Apps -> IDT HR Sensor -> Permissions -> activate ‘your locati on’ .
d. Turn on Bluetooth.
e. Open app. Activate sensor board by pushing the a ct ivation switch (Figure 6). Keep finger off sensor to

get a low data rate while pairing Android device with sen sor. App asks for Bluetooth pairing. After pairing

close app and reopen it.
f. After sensor re-programming unpair and pair again.
g. If Bluetooth does not connect, turn Bluetooth off / on and / or reboot Android device.

2. Open the app.

3. Put your finger on the heart rate sensor. Apply pressure until the activation switch on the bottom side of the
PCB (see arrow in Figure 6) clicks. Keep pressure until counter starts counting.

The pressure level sufficient to activate the switch is not required during measurement, as the sensor boa rd
stays active for about 30 seconds after the switch i s released. Less pressure on the blood vessels produce
better results.

Figure 6. PCB Activation Switch

4. The proximity function of the sensor deactivates / reactivates the red LED and heart rate measurement if the
finger is out of / back in range. This allows to relax or repositioning the finger without losing Bluetooth
connection.

5. When activated, the sensor measures the reflecte d LED light signals and transmits them to the Android
device which calculates and displays heart rate and S pO2.

6. A Finger Rest around the sensor (examples are shown i n F igure 7) distributes the force between sensor and
finger, improving the blood flow and accuracy of measurement.