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Dedicated clock CPU vs thread on an N2+?


Best Answer knut.tveitane, 22 March 2014 - 09:59 AM

If you synchronise the Netduino's clock with NTP at startup time, and then use a Timer object to trigger updates to the Nixie tubes/SPI signal (from the Timer event handler) as often as it is needed, you will have plenty of capacity for doing other work on the Netduino. No need to use a hardware RTC as long as you have Internet access and the NTP gives you sufficient accuracy.

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#1 remotewizard

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Posted 19 March 2014 - 02:54 PM

Work continues (slowly!) on my Nixie clock project.  Currently, it includes the following parts:

 

  • a conventional Windows service (running on an existing always-on PC) that periodically obtains the local weather forecast from Forecast.io, parses the results, and posts the one-word forecast for the next day to Xively
  • one (so far) Electric Imp with an Adafruit AM-2315 I2C temperature/humidity sensor, which will eventually reside outdoors; this periodically posts the current temperature and humidity to Xively
  • My Netduino (attached to an Edimax BR-6258n for WiFi access) running an MQTT client, subscribing to the forecast, temperature and humidity info on Xively.  When new data is received, the appropriate global variables are updated and action taken 
  • a lookup table on the Netduino that converts the one-word forecast ("snow") to a color ("white"); think the Gulf Building weather beacon in Pittsburgh, where lighting on the the top of the building changes color with the weather forecast.
  • currently, a tricolor LED to display the forecast color.  In the future, when I install my four DFRobot Nixie modules, I'll control the background colors of those instead
  • a RTC synced to NTP (currently by the Netduino), with an automatic adjustment for Daylight Savings time
  • finally, the four Nixie tubes which will display the clock time on request (I'll normally keep the neon part powered off, to increase the tube's lifespan.

 

It seems like a waste of the Netduino to run as a simple realtime clock, constantly updating the Nixies via SPI; I'd like to eventually add additional functionality to the Netduino (e.g. local room temperature sensor, smoke detectors, etc.) and don't want to burden the Netduino with gruntwork.  Would I be better off to move the strictly clock-related functions off to something like an ATTiny (or dedicated time clock chip), reserving the Netduino for more complex tasks?  Or am I worrying needlessly (as I often do)?

 

Did any of this make any sense at all?



#2 knut.tveitane

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Posted 22 March 2014 - 09:59 AM   Best Answer

If you synchronise the Netduino's clock with NTP at startup time, and then use a Timer object to trigger updates to the Nixie tubes/SPI signal (from the Timer event handler) as often as it is needed, you will have plenty of capacity for doing other work on the Netduino. No need to use a hardware RTC as long as you have Internet access and the NTP gives you sufficient accuracy.



#3 remotewizard

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Posted 23 March 2014 - 12:18 PM

I was hoping that would be the case, but it's nice to know for sure.  Thanks for taking the time to reply!






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