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Forum Index : Microcontroller and PC projects : New Micromite LCD clock
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| Talbit Senior Member  Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Geoff, you've done it again! What a beauty. But I'm going to have to adapt your program to update the display on the PPS mark. But it will need the GPS module with the PPS output, either the Globalsat EM-406A or the Fastrax UP501. Come on guys, I've shown you how to do it! It's someone else's turn. Talbit Talbit |
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| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Woops. On page 34 of the SC article, Geoff says "displays the time accurate to within a second". Then he says on his web site that the clock has "split second accuracy". I just had a look at the program and it looks like Geoff has addressed this issue by using a timer. I'll have to build it now! But I'm not quite sure how he updates the hour at the 60 minute mark. And what happens at the 24 hour mark? I'm sure it's all hidden in the code. It'll give me something to do! And I recall some testing I was doing with these GPS modules and the NMEA string doesn't always take the same amount of time to spit out. Geoff relies on this timing before he updates the time display. I'd be keen to hear comments on it's operation if someone builds it. Talbit Talbit |
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Geoffg Guru  Joined: 06/06/2011 Location: AustraliaPosts: 3167 |
I kept it simple for the magazine article to avoid having to go into a long winded explanation for the reader. The code in the magazine article will update the display about 300mS late (ie, the clock is about 300mS slow). In the code posted on my website (http://geoffg.net/Micromite_GPS_Clock.html) and on the SC website I optimised the code so that the display will only be about 10mS behind the real time. If you used the PPS output of a GPS module you could probably reduce that by a few milliseconds. I don't think that it really matters either way. The human eyeball watching the clock will not notice this very fine distinction - even a 300mS delay in updating the display would not be noticeable. Geoff Geoff Graham - http://geoffg.net |
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| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Thanks Geoff. You're right about the update delay not being visible. In fact with an LCD display, just the ambient temperature can slow things down a bit. Anyway, the main reason I wanted to use the PPS was to get my alarms as accurate as possible. I might build your new version and add my alarms and measure the real delays. Your new version looks so easy to knock up. That's the best part. Thanks again. Talbit Talbit |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
Hi Geoff, minor edit req'd for your 'clock' link. TimeZone is the offset of your local time from UTC. It can be positive or negative and it can be a fraction (for example, -6.5 is six hours thirty seconds before UTC). should be 30 minutes.
I'm really looking forward to reading your SC article - with a bit of luck it'll arrive tomorrow! Greg |
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| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Paceman, Well spotted. Geoff deliberately puts those things in to see if people read his stuff! Talbit Talbit |
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