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Andrew_G
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Joined: 18/10/2016
Location: Australia
Posts: 871

Posted: 02:48pm 23 Oct 2016

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Hi,
I'm starting to plan a Micromite (28 pin) device to monitor barometric pressure and plot daily/hourly trends (v useful for predicting weather at sea - often out of VHF range and certainly no internet). It will use a BMP180 and DS321 with the LCD Backpack. I've scoured the TBS history and have looked at Lew (and others') weather stations etc.
Some questions if I may:
- with the DS321 module - why the second set of headers (without pins)?
- I assume I can ignore the "32K" (signal output) and "SQW" (square wave output) header pins - at least for now - and use the remaining pins?
- with the BMP180, I see that Lew connects the SP1:CLK to pin 25 on the Micro. This is used by the LCD backpack - can they share it? (I have read Appendix D but not fully understood it - yet).
- I propose to take several readings (and average them) say every 30 minutes (unless a change is on and then it may be more frequent). This would give 6+ days of plot - more than enough. I'm thinking of an array with 320 values which would just be shuffled after plotting the lot (with say 30 minutes between plots - time is not an issue) (dropping the oldest / keeping the new one).
(In due course I may add an ambient light sensor etc)

Any suggestions?

Thanks, Andrew

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6269

Posted: 03:54pm 23 Oct 2016

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The BMP180 uses I2C not SPI for it's interface so that's pins 17 and 18 on the 28pin 'mite

Each I2C device has an address so many different devices can share the same bus.

Yes you can ignore the 32K and SQW pins on the clock.
I am guessing that the second set of pins on the clock module are simply an alternative pin arrangement and not used normally. I don't know your module so that's a bit of a guess.

Jim

VK7JH
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Andrew_G
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Joined: 18/10/2016
Location: Australia
Posts: 871

Posted: 05:17pm 23 Oct 2016

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Thanks Jim - ever helpful. Cheers, Andrew

mikeb

Senior Member

Joined: 10/04/2016
Location: Australia
Posts: 174

Posted: 07:26pm 23 Oct 2016

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Hi Andrew,

The second header connects to an Eeprom on board the module (assuming you are using the module we all know). 2 pins are for power, and ground, and the other 2 are for I2C communications. Otherwise, the Eeprom is not connected at all. Your choice.

Regards, Mike B.

There are 10 kinds of people in the world.
Those that understand binary and those that don't.

robert.rozee
Guru

Joined: 31/12/2012
Location: New Zealand
Posts: 2428

Posted: 10:48pm 23 Oct 2016

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on some (but not all) RTC+eeprom modules, i believe the second header is a passthrough of Vcc, ground, and I2C pins. This allows you to daisychain modules together. on grogster's E100 board you'll notice that the second header for the RTC module is not connected to anything, yet the eeprom on the module is still accessible.

cheers,
rob :-)

Andrew_G
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Joined: 18/10/2016
Location: Australia
Posts: 871

Posted: 12:34am 24 Oct 2016

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Mike and Rob, thanks for that.
It makes sense. I'll leave the second headers off.
I've populated a x320 array and shuffled new for old values and graphed it. The 'micro is plenty fast enough but I am nudging memory capacity. I'm using GeoffG's SuperClock so I'll strip variables and comments out and make it less generic (eg I only need three Clocks and eventually no GPS - it will go in my aluminium yacht which is a great Faraday cage).
I am really impressed with how easy it is to program and get a decent display.
Cheers,
Andrew

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