[time-nuts] TruePosition on the Arduino
eb4apl at gmail.com
Sun Jun 25 21:05:10 EDT 2017
Maybe I'm missing something, but Arduino programs are usually
distributed as source code. If this is the case, the I2C address of the
display should be not a problem. If the problem is due to the display
library used, you can use another library that can be initialized with
the right address.
I'm curious about the real problem.
El 26/06/2017 a las 2:29, Tom Miller escribió:
> This is an update to discussions off list with Ben and Chris regarding
> using the two line, 16 character display with the Packrats software on
> the Arduino to control the TruePosition GPS board.
> First, the ebay seller still has a few boards left and seems to take
> offers of $40 for them.
> Second, the display used with the Packrats software must use the I2C
> address of 0x3F to work. The display needs to use the PCF8574AT I2C
> I/O expander chip and not the PCF8574T. The later chip addresses
> between 0x20 to 0x27 and will not work with this software.
> Third, I picked up some of the "A" chips on ebay and they were marked
> as A chips but addressed wrong. If you are going to change out this
> expander chip, get them from someone like Mouser.
> Next step is to find a suitable housing for this assembly.
> Thanks all,
> ----- Original Message ----- From: "Ben Hall" <kd5byb at gmail.com>
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Sent: Tuesday, June 06, 2017 7:46 PM
> Subject: [time-nuts] TruePosition on the Arduino
>> Good evening all,
>> There is a saying: "a man with one watch knows the time, a man with
>> two is never sure." Clearly, this man wasn't a timenut and didn't
>> have GPS. ;)
>> I've been working on the Arduino code for the TruePosition boards
>> that quite a few of us have bought from the e-place.
>> It's my first real foray into both Arduino and the C language. (About
>> a million years ago I was reasonably competent with FORTRAN...the
>> 1977 version...) It's mostly working - I can receive and display
>> pretty much everything that comes out of the unit minus a few
>> parameters. I can display it all on three pages on a 4 line by 20
>> character I2C display. Currently, the pages are selected by grounding
>> out one of two pins, or having nothing grounded. Eventually, I'm
>> going to change this so that it changes display pages when a button
>> is pressed. I don't have lat/long display yet, nor can I handle
>> doing a survey, but those are coming.
>> My code probably would make a real programmer vomit, but hey, it
>> works. :)
>> Back to the man with multiple watches. I was having a very
>> frustrating issue with my TruePosition and Arduino code being one
>> second behind my other sources of time. I went round and round,
>> trying to figure out why the TruePosition thru the Arduino was a
>> second slow. In the end, it turns out that it wasn't slow...it was
>> correct...but that my other sources of time have errors.
>> I finally proved this to myself by firing up an old Trimble Lassen LP
>> GPS board unit equipped with a 1PPS tick light and serial
>> output...and it was clear that it matched the TruePosition after
>> correcting for the fact that my TruePosition / Arduino code only
>> updates the display when 1PPS is asserted high...but that the Lassen
>> LP displays the serial message before it becomes valid at the next
>> 1PPS tick.
>> I was slightly embarrassed...I should have known that the other
>> sources of time all had sources of error beyond my control. I should
>> have trusted the TruePosition as being the purest, least complicated,
>> and the path I knew the most about between GPS and my eyeballs.
>> So for a while...the statement was true. With my multiple sources of
>> time...I really didn't know the time. But it was also untrue, as
>> when I got agreement between two very "pure" sources of time, I knew
>> everything else was wrong. ;)
>> I'm getting to the point that once I've got the button logic working,
>> I'll send out my source to anyone who wants to take a look at it or
>> use it. I will stipulate one condition - you can't make too much fun
>> of how poorly programmed it is. ;)
>> thanks much and 73,
>> ben, kd5byb
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