Re: Selecting embedded Linux for a new medical device project (LONG)

"DavidK" <PleaseReplyTo@xxxxxxxxxxxxxx> skrev i meddelandet
news:rZXMi.122$LD2.46@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi,

I've just begun working on a new project for a medical device, and I'm in
the early stages of deciding which RTOS we'll use.

To summarize the device, it's a medical device that will have a graphical
user interface (and possibly a touchscreen), a control knob to set the
power
level, a footswitch, an RF power generator, and an 'applicator' that's
connected to the system by a long cable.

The doctor will use the device by setting the desired power level using
the
knob (the knob position is read by the software), and when the footswitch
is
pressed, the device will deliver the appropriate level of RF energy to the
patient via an applicator. During the 'treatment', the device will
display
the setpoint power level, the measured power level, the time in seconds
since the treatment was started, and the temperature of the patient's
tissue
that's being 'treated'. The device will emit a beep tone every three
seconds during 'treatment' to indicate that RF energy is being applied.
When the doctor deems the 'treatment' is complete, he will release the
footswitch, and the RF power will be turned off. Data aquisition
(temperature and measured power level) will be performed every 10ms or so.

Of course the final device, including its software, will be run through
rigorous testing and clinical trials as required by the US FDA. But it
would be nice to select an operating system that has been used
successfully
in safety-critical (such as medical) applications, so that I won't be the
first one going down that road with the OS we select.

At this stage, we have not decided which CPU will be used, but I suspect
it
will be a single-board computer (such as a PC/104 form factor) with an
Intel
x86 or compatible processor.

I am considering using embedded / RT Linux for this project, to help keep
costs down by avoiding operating system per-copy royalty charges. How
should I go about selecting a particular distro or Linux? I was reading
about uCLinux, but it doesn't seem to have been ported to Intel x86 CPUs
yet.

Any links or tips in selecting a particular version of Linux is
appreciated!

David K


It looks to me that you can solve your control problem in a small
Microcontroller
connected to a display unit which does not need to have any real time.

1 ADC channel to measure "knob".
1 ADC channel to measure temperature over NTC
1 Digital input to measure footswitch
1 Timer for beeper.
1 black box to generate RF power. (SPI?)
1 black box for applicator (What's an applicator?)
1 Communication channel to display unit.
1 measurement cycle per 10 ms.
115,200 BAUD UART => 115 characters per cycle
You need to transmit
* setpoint power level (2 bytes)
* the measured power level (2 bytes)
* the time in seconds since the treatment was started (2 bytes)
(Assume shorter than 16 hours)
* Temperature (2 bytes)
SPI to communicate with SD-Card.
EEPROM to handle Setup & Calibration.

Sounds like it easily could be done in an AVR
communicating with a display controller.

You did not mention the resolution/colourdepth of your screen.
This is quite important.
Also, what type of volume are you planning.
Just a few, and an off the shelf PC communicating with a USB device
doing the real measurement should do.
With some volume behind it, then there are several cheap ARMs with LCD
display.
(AT91SAM9261 is but one)



The displayunit can run Linux, but writing to a double buffered
screen without a large RTOS is probably not a big deal.

--
Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may not be shared by my employer Atmel Nordic AB



.

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