ECG plot using PCA10004/5

[Shrijit Mukherjee]

Hi, I was wondering if anyone has done this seemingly doable job of producing continuous ECG trace using PCA1004 and PCA10005 devices. My intended use case is this: Use one of PCA10004 or PCA10005 as Master and other as slave (GATT server and client). Use the Analogue input of the slave to connect to a ECG simulator (www.ms-gmbh.de/.../phantom_start.htm) and transmit data continuously to a PC , connected with the other device. Or, the PC may be connected to PCA10000 dongle as GATT client.

It may also be fine to use only one of the boards to transmit data (GATT server) and see it on a iOS device.

Has anyone done a similar task?

I see this post to be closely relevant but doesn't end successfully.

[cocoa]

Hi,

you need a specific ECG ADC, nRF51822 ADC has not the precision required for such task. ECG analog front end requires simultaneous sampling, 16-bit (minimum) delta-sigma ADC, gain amplifier with high common mode rejection and very low offset and drift, input bias current around 200 pA.

Sampling rate starts from 125 SPS to 8000 SPS

Use nRF51822 only as data transmitter and not as analog converter.

-c

PS: if used differently from an hobby device , FDA approval is required as medical device.

[Shrijit Mukherjee]

Yes, I agree. I have the front end solution for picking up the ECG but that's not I am concerned about in this post. If you see my post, I have said, at this stage I want to use a ECG simulator, nothing too medically sophisticated. Consider this as a simple problem: Transmit a 20 Hz sine wave using BLE nRF51822. Can I get some help? :)

I am not worried about any of the other concerns that you have raised, although they are valid. At this stage, I must have a proof-of-principle BLE based wireless link working.

I have worked quite a lot with analogue stuff and bench data converters but not so much this (digital/ wireless stuff). If I can interface nRF51822 with LabVIEW, even that is a start for me (I know some people have done it with other BLE modules).

[cocoa]

Hi, I thought you wanted to use the ADC port of nRF51 to convert analog signal.

If you are using a commercial AFE you should have some communication port (SPI and GPIO).

Use these to communicate the ADC conversions to nRF SPI or GPIO.

If you haven't comm ports, you can calculate the ADC sample rate that's fits with nRF51 data rate of your ble custom service.

-c

[Shrijit Mukherjee]

Please do bear with me as I am trying to go through a steep learning curve with this device and associated software development.

Let me simplify the task: Transmit a 50 Hz sine wave

According to the nRF51822 datasheets, there can be 250kbps, 1 Mbps, 2 Mbps data rates. I have run some of the example codes using Keil IDE and seen the RF outputs on a spectrum analyzer which was kind of a good thing (radio_test_example).

Now if I select, say, 1Mbps for data rate. So, if I want , say, 250 SPS sampling rate on a single analog channel with10-bit accuracy then I have 2500 bps data stream to send (per channel and I only want 1 channel for the initial task). This should be sufficient to transmit let's say 50 Hz sine wave quite easily?

I would like to get started with the above settings. So, once the connection has been established between the client and server, the server can continuously send data at 2.5 Kbps, much lower than the configured data rate.

Does this sound like a simple thing to do? It would be really helpful if I can get started with this simple system. I also want to be able to display this so I do need some kind of GUI. Is there something available that I can simply borrow, to start with?

Thanks

[cocoa]

Do you need to be BLE 4.0 compliant or a simple RF link is enough ?

-c