ECG plot using PCA10004/5

RE: ECG plot using PCA10004/5

Ole Morten — Tue, 04 Mar 2014 15:19:06 GMT

I'd strongly recommend you to take a look at nAN-36 and the accompanying code on GitHub. This shows how to build a custom service and send data.

You may also have use in looking at ble_app_hrs in the SDK, which shows how you can send heart rate data, using the standard Bluetooth SIG heart rate service.

Also, the User Guide for your kit shows how to just test the ready-made application, which may be useful to get a feel for how this works.

RE: ECG plot using PCA10004/5

cocoa — Sun, 02 Mar 2014 10:48:48 GMT

Hi,

I'm sorry but I do not use windows and Master Device.

Try to implement a BLE serial port : nRF UART

-c

RE: ECG plot using PCA10004/5

Shrijit Mukherjee — Thu, 27 Feb 2014 18:22:55 GMT

Thanks, I have been looking at that and other useful background readings. That article you have pointed to is certainly helpful.

Like I said, it will be really helpful if I could get some help for setting up a continuous data link between two BLE eneabled devices. I think it is something somebody has almost certainly attempted. I see some Youtube videos with continuous ECG on BLE so it is doable.

Can anyone please help me with some early code and whether I can link it to some GUI (something like a Serial interface between the Master device and PC, upon receiving data from the Slave)?

RE: ECG plot using PCA10004/5

cocoa — Fri, 21 Feb 2014 20:38:13 GMT

There is a useful post here : devzone.nordicsemi.com/.../how-do-i-calculate-throughput-for-a-ble-link.

Ole Morten explains all about a ble link throughput.

-c

RE: ECG plot using PCA10004/5

Shrijit Mukherjee — Fri, 21 Feb 2014 18:58:24 GMT

I do want it to be BLE complaint- hence invested in Nordic. But since I got no background, I want to go easy.

RE: ECG plot using PCA10004/5

cocoa — Fri, 21 Feb 2014 18:54:45 GMT

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

-c

RE: ECG plot using PCA10004/5

Shrijit Mukherjee — Fri, 21 Feb 2014 18:48:08 GMT

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

RE: ECG plot using PCA10004/5

cocoa — Fri, 21 Feb 2014 13:20:20 GMT

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

RE: ECG plot using PCA10004/5

Shrijit Mukherjee — Fri, 21 Feb 2014 10:13:50 GMT

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).

RE: ECG plot using PCA10004/5

cocoa — Fri, 21 Feb 2014 00:49:05 GMT

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.