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twofingers
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Joined: 02/06/2014
Location: Germany
Posts: 1526

Posted: 06:53am 18 Sep 2015

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There is already a thread for CLOCKTRIM but I think this is much easier.

Most of us own a DS3231 RTC modul which also outputs a very precise 32khz (32768hz) squarewave signal (32kHz TCXO).

With clocktrim value=0 I get the (wrong) 32742hz displayed (this means the MM is too fast!). After setting clocktrim value=-2 my MM2 works nearly perfect (Freq=32772).

' Clocktrim level for Micromite2/MMBasic
' determines the value for Option ClockTrim n
' using the DS3231 32768hz signal (32kHz TCXO).
' Released by twofingers@TBS 18.09.2015
' Provided AS IS. No warranty.
'
' You need only to connect a wire from
' DS3231/32kHz Pin to a MM2 (COUNT) pin (e.g. 16)

CLS
Option EXPLICIT
Dim integer freq,ctrim

SetPin 16,fin
Pause 2000
freq=Pin(16)

ctrim=Cint(freq-32768)/15
'Print freq, ctrim
If Abs(ctrim) < 10 Then
Option ClockTrim ctrim
Print "ClockTrim is set to "ctrim
Else
Print "Error! Please check 32khz signal. Freq="freq
EndIf

Download:2015-09-18_165241_Clocktrim.zip

Frequencies for different ClockTrim (-)values measured with MM2/MX170/28Pin at room temperature (22�C).
Each clocktrim value represents ~15hz (or 0,046% of 32768).

0 32742
1 32757 -15
2 32772 -15
3 32787 -15
4 32802 -15
5 32818 -16
6 32833 -15
7 32849 -16
8 32864 -15
9 32879 -15
10 32895 -16
11 32910 -15
12 32925 -15
13 32940 -15
14 32956 -16
15 32971 -15
16 32986 -15
17 33007 -15
18 33022 -15
19 33037 -15
20 33053 -16
21 33068 -15
22 33084 -16
23 33099 -15
24 33114 -15
25 33131 -17
26 33146 -15
27 33162 -16
28 33178 -16
29 33193 -15
30 33208 -15
-460 -15,33333333

Michael

causality ≠ correlation ≠ coincidence

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10067

Posted: 08:44am 18 Sep 2015

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Quote There is already a thread for CLOCKTRIM but I think this is much easier.

Certainly is - great bit of lateral thinking

One minor issue, you should remove CLS as we don't all have a display connected.

OPTION CLOCKTRIM isn't remembered so needs to be executed each time. However, with the new features in 4.7 it can now be included it in MM.STARTUP

twofingers
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Joined: 02/06/2014
Location: Germany
Posts: 1526

Posted: 09:12am 18 Sep 2015

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Thanks you for the kind words!

Quote One minor issue, you should remove CLS as we don't all have a display connected.

Yes! I used a BP170 with 2.4" TFT.

Quote OPTION CLOCKTRIM isn't remembered so needs to be executed each time. However, with the new features in 4.7 it can now be included it in MM.STARTUP

I thought it would be enough - in the most cases - if the Clocktrim value is at the beginning of the code. Moving it to the MM.STARTUP will be problematic because it takes 2sec (PAUSE 2000)! Who wants to wait for so long?

causality ≠ correlation ≠ coincidence

centrex

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Joined: 13/11/2011
Location: Australia
Posts: 320

Posted: 06:41pm 18 Sep 2015

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I have three 3231 modules all look the same but only one of them returns a trim figure the other two get the error message check the frequency.
They look identical and the 32 Khz pin on the 3231 is connected to the output pin.
Puzzled.

Cliff

twofingers
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Joined: 02/06/2014
Location: Germany
Posts: 1526

Posted: 11:05pm 18 Sep 2015

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centrex said They look identical and the 32 Khz pin on the 3231 is connected to the output pin.

to the output pin?

I have no idea. Can you check the signal on PIN1 (DS3231 chip)?
AFAIK the 32khz signal should be on (if powered by VCC):

Quote Control Register (0Eh)
Bit 7: Enable Oscillator (EOSC). When set to logic 0, the oscillator is started. When set to logic 1, the oscillator is stopped when the DS3231 switches to VBAT. This bit is clear (logic 0) when power is first applied. When the DS3231 is powered by VCC, the oscillator is always on regardless of the status of the EOSC bit. When EOSC is disabled, all register data is static. (MAXIM DS3231 manual p.13)

This is my DS3231:

Here is a updated version of the ClockTrim Demo:

DOWNLOAD:
2015-09-19_085543_Clocktrim1.zip

causality ≠ correlation ≠ coincidence

bigmik

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Joined: 20/06/2011
Location: Australia
Posts: 2946

Posted: 11:54pm 18 Sep 2015

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Hi Michael, All,

I have tried it on my SMD BackPack 170 which uses a DS3232 8pin RTC chip and it seems to work as well.

FYI here is where to link the 32kHz signal to Pin(16)

Regards,

Mick

Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<

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