Pulse Oximeter Teardown (incomplete)

[Kean Maizels]

I’ve ordered a few different OLEDs from AliExpress to experiment and see if they are a good replacement for LCDs – mostly on my internal projects like custom test equipment.

 

I also bought a few cheap Fingertip Pulse Oximeters to see if they were hackable, and they are.  We had a bit of a play with them at the space yesterday.  The firmware implements several screen layouts, including pulse waveforms and rotated views, which is quite nice.

 

Inside is a (1/4 split) yellow/blue 128x64 OLED connected to an MSP430F415 (wired in 8 bit parallel mode), plus a few odds and ends (2.5V LDO, analog switch, photo diode, pushbutton, speaker, and jellybeans).  The MSP430 FET (JTAG/ICSP) pins are nicely brought out to a 9 way 0.05” connector, and the first 7 pins are a perfect match for my standard MSP430 programming header.  The MSP430F415 is somewhat basic (16KB Flash, 512B RAM) and unfortunately has no UART.

 

Info and photos at http://www.kean.com.au/oshw/oximeter/

 

If there is interest, I’ll do a more thorough write up from my reverse engineering notes.  I’ve traced many of the interconnections, but it is still a somewhat incomplete analysis at this stage.

 

Kean Maizels

Kean Electronics - IT Consulting & Embedded Systems Design

Ph: 02 9482 5007 or 0414 245 326

 

[Madox]

If you were to hack it, what would you use it for?  Remove the photo diode and replace with another sensor, e.g. temperature and change it to a temperature display?

Actually silly me, the ISCP/JTAG/FET connector would probably make a better place to tack sensor modules onto...

Still question is - what would you make?

[Kean Maizels]

Not sure yet.  Was just thinking a small display device – maybe I2C or Serial comms to another CPU.

 

Unfortunately most of the MSP430 FET pins aren’t useable for other things like they are on AVR.

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[Gav]

Nice writeup, Kean.

I just got one delivered, but a cheaper type with 7-segment displays. Seems pretty cool and useful to calibrate any home-brew pulse sensors against. 

[Kris]

Why wouldn't you just measure your pulse with your fingers for calibration? :-)

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[Franc Carter]

On 10/04/13 09:29, Kris wrote:

Why wouldn't you just measure your pulse with your fingers for calibration? :-)

Ludite ;-)

Gav <the.mechat...@gmail.com> wrote:

Nice writeup, Kean.

I just got one delivered, but a cheaper type with 7-segment displays. Seems pretty cool and useful to calibrate any home-brew pulse sensors against.�

On 9 April 2013 19:49, Kean Maizels <Ke...@kean.com.au> wrote:

Not sure yet.� Was just thinking a small display device � maybe I2C or Serial comms to another CPU.

�

Unfortunately most of the MSP430 FET pins aren�t useable for other things like they are on AVR.

�

From: sydney-h...@googlegroups.com [mailto:sydney-h...@googlegroups.com] On Behalf Of Madox
Sent: Monday, 8 April 2013 10:01 PM
To: sydney-h...@googlegroups.com
Subject: [RnD] Re: Pulse Oximeter Teardown (incomplete)

�

If you were to hack it, what would you use it for? �Remove the photo diode and replace with another sensor, e.g. temperature and change it to a temperature display?

�

Actually silly me, the ISCP/JTAG/FET connector would probably make a better place to tack sensor modules onto...

�

Still question is - what would you make?

�

On Sunday, April 7, 2013 6:55:40 PM UTC+10, Kean Maizels wrote:

I�ve ordered a few different OLEDs from AliExpress to experiment and see if they are a good replacement for LCDs � mostly on my internal projects like custom test equipment.

�

I also bought a few cheap Fingertip Pulse Oximeters to see if they were hackable, and they are.� We had a bit of a play with them at the space yesterday.� The firmware implements several screen layouts, including pulse waveforms and rotated views, which is quite nice.

�

Inside is a (1/4 split) yellow/blue 128x64 OLED connected to an MSP430F415 (wired in 8 bit parallel mode), plus a few odds and ends (2.5V LDO, analog switch, photo diode, pushbutton, speaker, and jellybeans).� The MSP430 FET (JTAG/ICSP) pins are nicely brought out to a 9 way 0.05� connector, and the first 7 pins are a perfect match for my standard MSP430 programming header.� The MSP430F415 is somewhat basic (16KB Flash, 512B RAM) and unfortunately has no UART.

�

Info and photos at http://www.kean.com.au/oshw/oximeter/

�

If there is interest, I�ll do a more thorough write up from my reverse engineering notes. �I�ve traced many of the interconnections, but it is still a somewhat incomplete analysis at this stage.

�

Kean Maizels

Kean Electronics - IT Consulting & Embedded Systems Design

Ph: 02 9482 5007 or 0414 245 326

�

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�

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�

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Franc

[Gav]

I was actually thinking of the SpO2 level rather than the pulse, but perhaps that would be a very liberal definition of 'calibrate' if I'm using a DealExtreme sensor as the reference :-)

On 10 April 2013 09:44, Franc Carter <franc....@gmail.com> wrote:

On 10/04/13 09:29, Kris wrote:

Why wouldn't you just measure your pulse with your fingers for calibration? :-)

Ludite ;-)

Gav <the.mechat...@gmail.com> wrote:

Nice writeup, Kean.

I just got one delivered, but a cheaper type with 7-segment displays. Seems pretty cool and useful to calibrate any home-brew pulse sensors against. 

On 9 April 2013 19:49, Kean Maizels <Ke...@kean.com.au> wrote:

Not sure yet.  Was just thinking a small display device – maybe I2C or Serial comms to another CPU.

 

Unfortunately most of the MSP430 FET pins aren’t useable for other things like they are on AVR.

 

From: sydney-h...@googlegroups.com [mailto:sydney-h...@googlegroups.com] On Behalf Of Madox
Sent: Monday, 8 April 2013 10:01 PM
To: sydney-h...@googlegroups.com
Subject: [RnD] Re: Pulse Oximeter Teardown (incomplete)

 

If you were to hack it, what would you use it for?  Remove the photo diode and replace with another sensor, e.g. temperature and change it to a temperature display?

 

Actually silly me, the ISCP/JTAG/FET connector would probably make a better place to tack sensor modules onto...

 

Still question is - what would you make?

 

On Sunday, April 7, 2013 6:55:40 PM UTC+10, Kean Maizels wrote:

I’ve ordered a few different OLEDs from AliExpress to experiment and see if they are a good replacement for LCDs – mostly on my internal projects like custom test equipment.

 

I also bought a few cheap Fingertip Pulse Oximeters to see if they were hackable, and they are.  We had a bit of a play with them at the space yesterday.  The firmware implements several screen layouts, including pulse waveforms and rotated views, which is quite nice.

 

Inside is a (1/4 split) yellow/blue 128x64 OLED connected to an MSP430F415 (wired in 8 bit parallel mode), plus a few odds and ends (2.5V LDO, analog switch, photo diode, pushbutton, speaker, and jellybeans).  The MSP430 FET (JTAG/ICSP) pins are nicely brought out to a 9 way 0.05” connector, and the first 7 pins are a perfect match for my standard MSP430 programming header.  The MSP430F415 is somewhat basic (16KB Flash, 512B RAM) and unfortunately has no UART.

 

Info and photos at http://www.kean.com.au/oshw/oximeter/

 

If there is interest, I’ll do a more thorough write up from my reverse engineering notes.  I’ve traced many of the interconnections, but it is still a somewhat incomplete analysis at this stage.

 

Kean Maizels

Kean Electronics - IT Consulting & Embedded Systems Design

Ph: 02 9482 5007 or 0414 245 326

 

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Franc

[betasy...@gmail.com]

Hello! I am trying to work on this right now... But I am lost on how I can extract the data from the pulse oximeter device and send it to a database hosted in my computer. It is only for educational purposes. I am planning to extract the data from the pulse oximeter device and send it to the arduino board for processing. I am planning on using an ethernet shield for sending the extracted data into the database hosted in my personal computer.

[Mark Pearson]

I am using the cooking hacks http://www.cooking-hacks.com/ehealth-sensor-shield-biometric-medical-arduino-raspberry-pi board to record spo2 to a database. I found connecting the sensor to the raspberry-pi unreliable due to timing issues, so read the data with the arduino and then record the data on the raspberry-pi, with a web interface to control it.

I can send you more details directly if you are interested.

Mark

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[System Developer]

Hello Mark, thank you for your reply. I am planning to extract data from this pulse oximeter http://www.ebay.com/itm/OLED-Finger-Pulse-Oximeter-spo2-monitor-Fingertip-Oxygen-yk-80a-New-/251548620002 so that ay arduino will be able to send data into the database using an ethernet shield. I looked inside the pulse meter and it uses this board yk-80b-mainsp02 v2.3.1. It has the following on it, RST, TCK,TMS, TDI,GND,V,RX,Tx. I am assuming that I have to tap wires from any of these as an input to my arduino for data extraction. However, I am lost on which should it tap. I would appreciate any help from you.

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[System Developer]

this is what the insides of the pulse oximeter looks like. http://www.kean.com.au/oshw/oximeter/

[Brett]

Here's where it's time to find a data sheet on it.

GND is reasonably obvious - you WILL need it.

V is V in, power in to power the module - you will need it.

RX and TX are serial communication wires - most probably they are for a TTL level serial UART.

RST = likely ReSeT.

TCK = T ClocK

TMS = T Master Send

TDI = T Data In

These most likely form an SPI-like interface. 

So you have two serial interfaces, you really just need to figure out if a) both are active, and b) how to choose between them (if you need - they may be both active).

good luck

[Mark Pearson]

If you are lucky the data going to the oled is echoed on the interface pins. Otherwise the pins are only for programming the controller and you will have to decode the data sent to the oled. The cooking hacks unit reads data directly from the LED display.

[Ada Lim]

On Fri, Aug 29, 2014 at 6:48 AM, Brett <brett...@hotmail.com> wrote:

> RST = likely ReSeT.
> TCK = T ClocK
> TMS = T Master Send
> TDI = T Data In
> These most likely form an SPI-like interface.

The naming of the pins is very reminiscent of something.

oh, that's right, what kean said, TI's FET (JTAG/ICSP) interface.

[betasy...@gmail.com]

Still on the process. I hope the the data is echoed on the interface pins And it would be very unfortunate if the interface pins are only just for programming the controller. By any chance, have you tried looking the insides of the ehealth pulse oximeter unit? I can see that it has a cable on it to be connected to the ehealth shield sensor. It has ten pins if I am not mistaken, I am just wondering if you could share where the cable pins are tapped inside the pulse oximeter?

On Sunday, April 7, 2013 4:55:40 PM UTC+8, Kean Maizels wrote:

[Mark Pearson]

The ehealth just decodes the 7 segment data. The cable is soldered directly to the display - when I got the unit I was not happy with the cable length and changed it to a ribbon cable. It has 8 data lines, gnd and 3.3v.
The data is sampled at the screen refresh rate which is why the timing is critical.

[Nick Johnson]

As Ada says, tck, tms, and tdi form the JTAG/SWD interface for reprogramming the microcontroller. I would ignore those and focus on the UART.

On Fri, 29 Aug 2014 09:12 Mark Pearson <pears...@gmail.com> wrote:

The ehealth just decodes the 7 segment data. The cable is soldered directly to the display - when I got the unit I was not happy with the cable length and changed it to a ribbon cable. It has 8 data lines, gnd and 3.3v.
The data is sampled at the screen refresh rate which is why the timing is critical.

--

[Ada Lim]

On Fri, Aug 29, 2014 at 6:19 PM, Nick Johnson <arac...@notdot.net> wrote:
> As Ada says, tck, tms, and tdi form the JTAG/SWD interface for reprogramming
> the microcontroller. I would ignore those and focus on the UART.

One of the UART pins (TX) is not connected. It's not clear how the
directions are named, and I haven't looked at the F415 datasheet to
see what pin RX is hooked up to.

I guess the next obvious step would be to hook up a logic analyser to
the RX pin and see if it talks at all, but kean's description of the
F415 (no UART) does not inspire.

The question arises: what is the actual goal? What data are you
trying to collect?

[Julian Sortland]

I think the original idea was to harvest and use the OLED display, and other parts.

Julian VK2YJS / AG6LE.

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[Kean Maizels]

Correct – I just wanted more OLEDs to play with.

I didn’t detect any serial data on those test pads, and didn’t investigate further.

It may be possible to intercept the screen updates (SPI or I2C, I don’t recall).

 

Kean