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WhiteWizzard
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Posted: 26 December 2015 at 8:48am | IP Logged Quote WhiteWizzard

I have used RFM12 wireless modules connected to a 28pin SMD MicroMite and used TMP102s as the temp sensor. Was personally using 868MHz modules as less interference than with the 433MHz ones.

The only thing is, you need to write the 'configuration' sequence to the RFM12 modules rather than the MM having inbuilt support. However, with the use of LIBRARY command (and the information for the startup sequence for the RFMs) then you can end up with an easy (and legal) RF link for remote sensors.

Use the CPU sleep command too and battery power becomes a reality. . . .

WW

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robert.rozee
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Posted: 26 December 2015 at 12:39pm | IP Logged Quote robert.rozee

the 433MHz band is referred to as LPD433 (low power device 433 MHz) and requires no licence for use in many countries:
https://en.wikipedia.org/wiki/LPD433
for the average person, the most familiar use of this band is for garage door controllers, green button Merlin remotes, for example. it is also shared with amateur radio operators (70cm, 430-440MHz).

the first four channels of the HC-12 module fall within this band. the default power output of the HC-12 is 100mW, while in australia and new zealand the maximum power allowed is 25mW. however, the antenna supplied is a helical (20-turn, 4.5mm diamater, 20mm length) that is likely to attenuate the output to be within the 25mW limit:
http://www.cqham.ru/spiral.htm
the bandwidth of the transmission is also quite wide (400kHz), which spreads this power out quite bit, again helping to keep within the regulations.

also of note: the HC-12 only transmits when there is data sent to it. so if transmitting (for example) a temperature reading every minute, transmission will only consist of a short 'blip' now and then. this mode, in itself, is unlikely to interfere with other users such as remote controls or voice.

conclusion: using the supplied 20mm helical antenna the HC-12 should be ok to operate in australia or new zealand on channels 1 to 4 (channel 1 is the factory default). so no configuration needs to be sent to the unit. setting a channel number above 4 is best avoided without first checking the local regulations, as is attaching a 'real' antenna. and finally, avoid sending data continuously to be courteous to other users of the band.

UK and american users may with to chime in with details of their own local regulations.


cheers,
rob :-)
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lew247
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Posted: 26 December 2015 at 6:27pm | IP Logged Quote lew247

Thanks everyone, everything is being taken in and all advice greatly recieved :)
I'm actually in Manchester in the UK

I think I'll start off with probably a 5 inch touchscreen lcd, showing the day/date time etc from a gps module.

This should be a big enough screen to allow me once I figure out how (or is someone posts examples) of adding an analogue type time display on the screen, but it would have to have decent hands, not sticks if that makes sense

Later on once I've learnt a bit more I can add the temperature sensor and some rf modules to recieve the outside temp humidity and so on.

I really love the idea of an ultrasonic wind speed/direction being added at some stage but this will be way way in the distant future, I've seen some arduino projects doing that and it looks really complicated (the coding)

What I'd like to do with the lcd display if it was possible and I really dont know if it is or if its going to be too hard to program - is maybe have a background picture (jpg or similar) read off an sd card and the clocks drawn over the top
probably way too advanced.

I'm going to buy the MicroMite+ Explore 64 as soon as Christmas is over and start playing with that and a display to i can start learning.

I decided to buy that one as it should have enough pins and power to do most of what I want it to do, although I may have to get some smaller micromites to work with the remote modules, no idea yet
but I'm going to start small and work up. (hopefully)

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lew247
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Posted: 03 March 2016 at 9:51am | IP Logged Quote lew247

Really simple question but I cannot find the answer anywhere (not even in the manual)

When making a circuit that will not have in circuit programming -

Do I have pin 1 connected to 3.3V or do I connect it through the 10K resistor or do I leave it unconnected?

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matherp
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Posted: 03 March 2016 at 10:08am | IP Logged Quote matherp

Page 7 in the latest manual

Personally I wire to VCC with 10K and then have a switch to GND to allow easy resetting
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lew247
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Posted: 03 March 2016 at 10:31am | IP Logged Quote lew247

Thanks matherp
I did read that which is why I asked, it doesn't make it clear if it HAS to be connected to +V or not (not in my mind anyway)

If I get what you said right, I connect it via the 10K resistor and then I can have a switch anywhere connected to ground and pin 1 and if I want to reset the micromite I press the switch

If I have autorun turned on, will that reset the micromite and restart the program once the switch is turned off?

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matherp
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Posted: 03 March 2016 at 10:33am | IP Logged Quote matherp

Quote:
If I have autorun turned on, will that reset the micromite and restart the program once the switch is turned off?


Yes: just use a simple push-button switch
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Grogster
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Posted: 03 March 2016 at 10:48am | IP Logged Quote Grogster

As far as I know, MCLR(pin1) must be pulled high for the MCU to run. I am not sure if it has anything internal in the way of pull-up - I would have to look at the Microchip datasheet. It would not be a good idea to leave it floating.

So, in a nutshell, MCLR must be pulled high, yes.

It is generally good practice to use the somewhat ubiquitous 10k as the pull-up on this pin. As this pin is active low, and if left to float, it could result in many an unhappy project, as the MCU would be forever restarting at odd and unpredictable times - not a good thing for one's sanity.

For the sake of a couple of tracks, I always include the ICSP pads and tracks, weather I think I will ever need them again or not. Pretty much mandatory for any of the SMD chips, but you can get away without the ICSP header on the DIL chip I guess, as it is simple enough to swap out to program etc.

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lew247
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Posted: 04 March 2016 at 9:10am | IP Logged Quote lew247

Another what to most is probably a stupid question, but I'd like to be positive

Pin 28 analog power - does this need to be connected to the +3.3v as well, or can I just use it to only power an analog device? (pot used in a speed sensor)

Also pin 27 analog ground - does this need to be connected the the normal ground or can I use it as the ground for the analog device?
The manual says it can be used as a clean ground but not sure if it "has" to be connected to the normal ground.
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matherp
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Posted: 04 March 2016 at 9:40am | IP Logged Quote matherp

Quote:
Pin 28 analog power - does this need to be connected to the +3.3v as well


Yes, but see the Colour Maximite circuit (pin 30) for a better arrangement

Quote:
Also pin 27 analog ground - does this need to be connected the the normal ground


Yes. To get good analogue readings makes sure 27 and 28 are decoupled very close to the pins
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lew247
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Posted: 04 March 2016 at 10:40am | IP Logged Quote lew247

Thank you
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Grogster
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Posted: 05 March 2016 at 12:55am | IP Logged Quote Grogster

lew247 wrote:
Another what to most is probably a stupid question, but I'd like to be positive


There are no stupid questions, just stupid people who don't ask questions in the first place.

All your questions so far are very valid ones - don't run yourself down.

EDIT: Following up a little on your posts above, I never think it is a good idea to make MCU power pins a current path. That is, to feed power into one power pin, and suck power off at another power pin for something else. It seems to be generally accepted that all power and ground pins have to be connected together. That is just me though, but I expect that at least some other members here would also agree - I hope!

The analogue ground circuit(10R + 100N to GND) that Geoff uses in his MM+ and Maximite series of units are certainly the way to go if you expect to be making any serious analogue measurements. Otherwise, I just directly connect AGND to the surrounding ground-plane, and A3v3 directly to standard rail voltage without the 10R and 100N.

It does very much depend on what you plan to do.

In other words, if you plan to use analogue measurements in your project, then use the 10R+100N. If you know you won't be using any analogue features, then just directly ground the AGND pin, and connect A3v3 directly to the supply voltage. If in any doubt as to what you are going to end up doing, then include the 10R+100N.

Edited by Grogster on 05 March 2016 at 1:02am


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