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MSP430FR4133 Launchpad Enough Memory, DAC needed for ECG Senior Design Project?

Jeffrey Frye
Prodigy 70 points

Other Parts Discussed in Thread: MSP430FR4133, DAC7760

Hi all,


I am getting started on my Senior Design Project with my group. We are planning on building an ECG Simulator and then having the actual circuit to filter out the signal and output it onto an Android tablet for a "doctor" to take notes and draw stuff on the signal.

I will try to be very clear so that I can get as much advice as possible. I am working mainly on the simulator part in the beginning. I will be taking the open data from PhysioNet since they have several databases. I was planning on using about ten different records, up to a minute each. They have an option to print out the sample in text, which has anywhere between 150-350 samples per second. So for a minute, there will be about 21,000 lines of data for each sample.
The user would be able to use push buttons to scroll through the available sample signals, seeing the options on an LCD display, and then the microcontroller would output the signal, which would be dealt with after being output.

SO, I saw the MSP430FR4133 LaunchPad since it comes with two push buttons and a small LCD display. The struggle I am having is that I am wondering if you think I'll need a separate DAC to make the digital data into an analog signal to output to the electrode leads for the ECG. Also, is there enough memory on the microcontroller to store up to 10 of these sample signals?

If you have any input or advice at all, I will be very grateful. Let me know if you need to me to explain more clearly a part of the project.

Thank you very much.

  • 0
    TI__Prodigy 485 points

    Hi Jeffrey,

    What is the accuracy of the analog signal that you want to output?  If you need high accuracy, I think a high resolution DAC will be better. Otherwise, you can also use PWM timer as a DAC. For this solution, you can refer to our application note SLAA116(http://www.ti.com/lit/an/slaa116/slaa116.pdf).

    MSP430FR4133 has 15.5KB FRAM that supports high speed data read or write with lower power consumpution. Based on your description, there will be 210,000 lines of data for 10 sample signals. This is lots of data and you'd better have one external FLASH to store the data. If the data size is not so large, you can use data compression algorithm(eg. ADPCM) to compress the data and then store on MCU.

    Best Regards,
    Darren Lu

  • 0 in reply to Darren Lu
    Prodigy 70 points

    Since it is am ECG signal, we do want it to be fairly accurate. Is there a high resolution DAC that you recommend? Also, since the data is just a few millivolts and of a decimal value, would I need to scale it for the DAC?

    Is there any flash that TI sells that could suffice? How easy is it to interface the Flash with the MSP430 in this case?

    I assume I could have both the Flash and DAC hooked up at the same time? 

    Thanks all your help.

  • 0 in reply to Jeffrey Frye
    Guru 25210 points

    Jeffrey Frye said:
    Is there any flash that TI sells that could suffice? How easy is it to interface the Flash with the MSP430 in this case?

    I would recommend a SPI flash device. TI doesn't sell these, but plenty of others do. It is not difficult to interface to these (4 wires required, use USCI in SPI mode to communicate with it).

    Jeffrey Frye said:
    Also, since the data is just a few millivolts and of a decimal value, would I need to scale it for the DAC?

    I would recommend scaling the signal AFTER the DAC, with an gain circuit with gain < 1. This allows you to keep all the resolution available in the digital samples.

    Jeffrey Frye said:
    Is there a high resolution DAC that you recommend?

    Look for one with a SPI interface. Something like DAC7760 might suit your needs.

    Jeffrey Frye said:
    I assume I could have both the Flash and DAC hooked up at the same time? 

    Yes. For easiest interface, put them on separate USCI channels.

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